University of Southern California Dissertations and Theses

A study of the reaction of 2,4-dinitrobenzene-sulfenyl halides with ketones

(USC Thesis Other)

A study of the reaction of 2,4-dinitrobenzene-sulfenyl halides with ketones

PDF

Download

Open document

Flip pages

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content A STUDY OF THE REACTION OF 2,4-DINITROBENZENE- SULFENYL HALIDES WITH KETONES A Dissertation Presented to the Faculty of • the Graduate School The University of Southern California In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy ty Milton M. Wald July 1954 UMI Number: DP21777 All rights reserved IN FO R M A TIO N TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI DP21777 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 -1 3 4 6 VJv 0 C. '6S VV :o7 This dissertation, w ritten by Milton Max Wald under the direction o fh l& G u id a n c e Committee, and approved by a ll its members, has been pre sented to and accepted by the F aculty of the Graduate School, in p a rtia l fu lfillm e n t of re quirements fo r the degree of 3 ^ D O C T O R O F P H IL O S O P H Y Assistant Dean Dale 2 9 .....J u lX ...1 9 ^ i4 -. Guidance Committee Chairmait L/Z-L r/f .an > ACKNOWLEDGMENT The writer wishes to acknowledge gratefully the assistance which was made possible by a grant from the National Science Foundation in partial support of this work . • TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION . . . . ........... 1 II. THE QUANTITATIVE DETERMINATION OF SULFENYL HALIDES................. 4 Introduction ..................... 4 Discussion ............................. 5 Experimental ................... .... 8 Preparation of Reagents .............. 8 Titration Using Aqueous Reaction Media . 13 Titrations Involving Anhydrous Reaction. Media . . . . . . ...... 14 Blank Determinations.............. 19 Titrations of Sulfenyl Halides Other than 2,4-Dinitrobenzenesulfenyl Chloride ......... 23 The Effect of Dissolved Oxygen on the Determination of Sulfenyl Halides . . 23 Titrations of Sulfenyl Halides in the Presence of Substances Capable of Possible Interference . . .......... 29 Determination of Varying Amounts of 2,4- Dinitrobenzenesulfenyl Chloride ... 32 • iV CHAPTER PAGE III. THE REACTION OF 2,4-DINITROBENZENESULFENYL CHLORIDE WITH ACETONE................. 35 Introduction ................. 35 Discussion . . ....................... 35 Experimental ......... 51 Preparation of Reagents . .......... 51 Completeness of Reaction of 2,4- Dinitrobenzenesulfenyl Chloride and Acetone . ....................... 52 Independent Synthesis of 2,4-Dinitro- phenyl Acetonyl Sulfide ....... 53.: Independent Synthesis of 2,4-Dinitro- phenyl Phenacyl Sulfide ............ 53 Preparation of the 2,4-Dinitrophenyl- hydrazone of 2,4-Dinitrophenyl Acetonyl Sulfide . 53 Preliminary Rate Studies Using Small Excess of Acetone................. 5^ ; Preliminary Rate Studies Using Large Excess of Acetone .......... 55 Regular Rate Studies Carried Out in Transparent Flasks ... ............ 56 Effect of Volume Changes During Mixing . . . . . .of. Solutions .and Ad justing ..of ... . . . . ____ '.V CHAPTER PAGE Temperature....................... 58 Regular Rate Studies Carried Out in Black. Flasks....................... 58 ■ Attempted Aluminum Chloride Catalysis of the Reaction of 2,4-Dinitrobenzene- sulfenyl Chloride with Acetone .... 65 Attempted Pyridine Catalysis of the Re action of 2,4-Dinitrobenzenesulfenyl Chloride with Acetone ........ 66 Reaction of 2,4-Dinitrobenzenesulfenyl Chloride with Pyridine ............. 67 Attempted Catalysis of the Reaction of 2.4-Dinitrobenzenesulfenyl Chloride and Acetone with Ultraviolet Light . . 68 Reaction of Isopropenyl Acetate and 2.4-Dinitrobenzenesulfenyl Chloride . 69 Rate Studies Using Isopropenyl Acetate . 69 Isolation of Product from Rate Runs ... 69 IV. THE REACTION OF 2>4-DINITROBENZENESULFENYL CHLORIDE WITH ACETONE IN METHYL ACETATE . 96 Introduction ........ .......... 96 Discussion... ................ 96 Experimental ...... ............... 134 . Preparation of. Reagents . ... ... . . .. .13.4. vi CHAPTER PAGE Identification of Product and Study of Completeness of the Reaction of 2,4- Dinitrobenzenesulfenyl Chloride with Acetone in Methyl Acetate ............ 136 Titration of 2,4-Dinitrobenzenesulfenyl Chloridetin Methyl Acetate ............ 137 ; Pseudo Rate Run to Check Evaporation Losses . . . ; ................... 137 Preliminary Rate Studies ................ 137 ; Rate Studies Without Added Acid .... 139 Runs with Excess Hydrogen Chloride Added 140 Possible Reaction of 2,4-Dinitrobenzene sulfenyl Chloride with p-Toluenesulfonic Acid . .............................. 14Q Runs with Added p-Toluenesulfonic Acid . 142 Possible Reaction of 2,4-Dinitrobenzene- I sulfenyl Chloride with Mercuric Chloride . .......................... 142 Rate.Rhn with Added Mercuric Chloride . 142 ; Possible Interaction of 2,4-Dinitroben zenesulfenyl Chloride with Pyridine . 142 Interaction of 2,4-Dinitrophenyl 41- ' Dimethylaminophenyl Sulfide with 2,4- ! i - - ... - Dini trobenzenesulf enyl-Chloride- -. . ---.---145- CHAPTER PAGE Rate Studies with Limited Aounts of Hydrogen Chloride Added ............ 147 Conductivity Studies . . . ............ 150 Bromination of Acetone in Methyl Acetate 150 Reaction of 2,4-Dinitrobenzenesulfenyl Chloride with Isopropenyl Acetate in Methyl Acetate .............. 152 Rate Studies at Temperatures Other than 5 0 ° ............. 153 Rate Studies Utilizing Ketones Other than Acetone....................... 154 V. THE REACTION OF 2,4-DINITROBENZENESULFENYL BROMIDE WITH ACETONE ............ 203 Introduction ............... 203 Discussion ........................... 203 Experimental........... 216 Preparation of Reagents . .......... 216 Attempted Rate Studies of the Reaction of 2,4-Dinitrobenzenesulfenyl Bromide with Acetone....................... 221 Reaction of 2,4-Dinitrobenzenesulfenyl Bromide with Acetone: Determination of Products .......... 221 . Titration of Bromoaeetone ___ . . 226 viii CHAPTER PAGE Reaction of 2,4-Dinitrobenzenesulfenyl Bromide with Acetone in Methyl Acetate.............................. 227 Effect of Oxygen on Reaction of 2*4- Dinitrobenzenesulfenyl Bromide and Acetone......... 229 Reaction of 2*4-Dinitrobenzenesulfenyl Bromide with Acetone in Sunlight . . 230 Reaction in the Presence of Diphenyl- methane ............... 231 Possible Reaction of 2,4-Dinitrobenzene sulfenyl Bromide with Hydrogen Bromide 232 Competitive Reaction of 2,4-Dinitroben- zenesulfenyl Bromide and Bromoacetone with 23-Dinitrothiophenol..... 233 VI. RELATED STUDIES.............' ............ 235 The Reaction of 2,4-Dinitrobenzenesulfenyl Thiocyanate with Acetone ............ 235 Introduction ........•............ 235 Discussion ......................... 236 Experimental ......................... 239 Preparation of Reagents ............ 239 Preliminary Rate Studies ............ 239 •Regular Rate Studies- .. . ...... - ---240 ix CHAPTER PAGE Reaction in Methyl Acetate .......... 245 The Reaction of 2,4-Dinitrobenzenesulfenyl Chloride with Acetoacetic Ester .... 246 Introduction ................... 246 Discussion ............. 246 Experimental ........................ 247 Preparation of Reagents ............ 247 Rate Studies . ...................... 247 The Reaction of 2,4-Dinitrobenzenesulfenyl Chloride with Acetone in Different : Solvents . . . ........................ 247 ■ Introduction.................. 247 Discussion ............................ 249 Experimental ............................ 254 Preparation of Reagents .............. 254 Rate Studies ........................ 255 : Rate Study in 1,2-Dimethoxyethane . . 258 Miscellaneous Studies .................... 259 Solubility of Certain Salts in Methyl Acetate....................... 259 Discussion ........ ........ 259 Experimental ........................ 259 ; The Decomposition of 2,4-Dinitrobenzene- sulfenyl Chloride in Sunlight - ---..263 .X CHAPTER PAGE Discussion ..................... 263 Experimental....................... 263 Competitive Reactions .................. 267 Discussion .......................... 267 Experimental ........................ 268 VII. SUMMARY ............................. 27I REFERENCES . . . ...................... 280 LIST OP TABLES TABLE PAGE I. Titrations Using Aqueous Reaction Media . 15 II. Titrations Using Sodium Sulfite ........ 16 * III. Titrations Using Anhydrous Reaction Media. 17 IV. Blank Determinations Using Added Hydrogen Chloride and Acetic Acid Saturated with A i r ................................. 20 V. Blank Determinations Using Added Hydrogen Chloride and Nitrogen-Swept Acetic Acid Under the Typical Conditions Used in the Sulfenyl Halide Determination ... 24 VI. Titration of Other Sulfenyl Halides . . . 25 VII. The Effect of Dissolved Oxygen ........ 27 VIII. Determination of 2,4-Dlnitrobenzenesulfenyl Chloride in the Presence of Other Substances . ..................... 30 IX. Titration of Different Amounts of 2,4- Dinitrobenzenesulfenyl Chloride .... 34 X. Summary of Rate Runs Using Excess Acetone. 44 XI. Effect of Volume Changes During Mixing of Solutions and Adjusting of Temperature . 59 XII. Experimental Data for Run 1 ........... 71 XIII. Experimental Data for Run 2 ........... 72 xii ~ TABLE PAGE XIV. Experimental Data for Run 3 ............ 73 XV. Experimental Data for Run 4 ....... 74 XVI. Experimental Data for Run 5 ............ 75 XVII. Experimental Data for Run 6 ............ 76 XVIII. Experimental Data for Run 7 ............ 77 XIX. Experimental Data for Run 8 ............ 78 | XX. Experimental Data for Run 9 ............ 79 XXI. Experimental Data for Run 10 ...... . 80 XXII. Experimental Data for Run 1 1 ............ 8l XXIII. Experimental Data for Run 1 2 ............ 82 XXIV. Experimental Data for Run 13 ' ............ 83 XXV. Experimental Data for Run 1 4 ............ 84 : 1 XXVI. Experimental Data for 'Run 1 5 ............ 85 XXVII. Experimental Data for Run 16 .......... 86 XXVIII. Experimental Data for Run 1 7 87 • XXXIX. Experimental Data for Run 18 .......... 88 1 1 XXX. Experimental Data for Run 1 9 ............. 89 . XXXI. Experimental Data for Run 20 ............ 90 1 XXXII. Experimental Data for Run 2 1 ............ 91 ! XXXIII. Experimental Data for Run 2 2 ............ 92 XXXIV. Experimental Data for Run 23 .......... 93 XXXV. Experimental Data for Run 24 .......... 94 XXXVI. Experimental Data for Run 25 ...... . 95 L XXXVII. Summary- of. Runs_Carr.ied-out-at. -50° and.__________ 1 xiii TABLE PAGE with No Added Acid......... 100 XXXVIII. Summary of Runs Carried Oilt at 50° with Excess Added Acid ........ 104 XXXIX. Summary of Runs Carried Out at 50° with Limited Amount of Added Acid . . . 112 XL. Pit of First Order Data to Equation 8 . . 119 XLI. Summary of Runs at Temperatures Other than 50° ......... 126 XLII. Summary of Data for Arrhenius Plots . . . 128 XLIII. Rate Runs at 50° Using Ketones Other Than Acetone...................... 133 XLIV. The Titration of 2,4-Dinitrobenzenesulfenyl Chloride in Methyl Acetate .......... 138 XLV. Apparent Interaction of 2,4-Dinitrobenzene- sulfenyl Chloride with Pyridine .... 146 XLVI. The Reaction of 2,4-Dinitrobenzenesulfenyl Chloride with Acetone in the Presence of 2,4-Dinitrophenyl 4'-Dimethylaminophenyl Sulfide............................. 148 ! XLVII. Conductivity D a t a ........... 151 XLVIII. Experimental Data for Run 26 ...... . 157 XLIX. Experimental Data for Run 2 7 ...... 158 L. Experimental Data for Run 2 8 ...... 159 LI. Experimental Data .for^Run 30 . . . . . ._. -l6o. TABLE PAGE LII. Experimental Data for Run 29 • • . . . . 161 LIII. Experimental Data for Run 54 • • .... 162 LIV. Experimental Data for Run 31 « • ' .... 163 LV. Experimental Data for Run 32 « • .... 164 LVI. Experimental Data for Run 33 • • .... 165 LVII. Experimental Data for Run 34 « * . . . . 166 LVIII. Experimental Data for Run 35 • • .... 167 LIX. Experimental Data,for Run 36 • • .... 168 LX. Experimental Data for Run 37 • • .... 169 LXI. Experimental i Data for Run 38 • • .... 170 LXII. Experimental Data for Run 39 * • ..... 171 LXIII. Experimental Data for Run 40 • • .... 172 LXIV. Experimental Data for Run 41 • • .... 173 LXV. Experimental Data for Run 4 2 • • .... 174 LXVI. Experimental Data for Run 43 • • .... 175 LXVTI. Experimental Data for Run 44 • • .... 176 LXVIII. Experimental Data for Run 45 • « .... 177 LXIX. Experimental Data for Run 46 • • .... 178 LXX. Experimental Data for Run 47 • ♦ .... 179 LXXI. Experimental Data for Run 48 • • .... 180 LXXII. Experimental Data for Run 49 • • .... 181 LXXIII. Experimental Data for Run 55 • • .... 182 LXXXV. Experimental Data for Run 50 • • .... 183 .■ -LXXV... Experimental- Data for-.Run .51 __________ 184 .X V TABLE PAGE LXXVI. Experimental Data for Run 5 2 ........ 185 LXXVII. Experimental Data for Run 53 ...... . 186 LXXVIII. Experimental Data for Run 5 6 ........ 187 LXXIX. Experimental Data for Run 5 7 ........ 188 LXXX. Experimental Data for Run 5 8 ........ 189 LXXXI. Experimental Data for Run 59 ...... . 190, LXXXII. Experimental Data for Run 6 0 ........ 191 LXXXIII. Experimental Data for Run 6l . ........ 192 LXXXIV. Experimental Data for Run 62 ...... . 193 LXXXV. Experimental Data for Run 63 . . . . . . 194 LXXXVI. Experimental Data for Run 6 4 ........ 195 LXXXVII. Experimental Data for Run 6 5 ........ 196 LXXXVIII. Experimental Data for Run 6 6 ........ 197 LXXXIX. Experimental Data for Run 6 7 ........ 198 • XC. Experimental Data for Run 68 . ....... 199 XGI. Experimental Data for Run 6 9 ........ 200 XCII. Experimental Data for Run 70............ 201 ; XCIII. Experimental Data for Run 7 1 ........ 202 XCIV. Synthesis of 2,4-Dinitrobenzenesulfenyl Bromide...................... 218 XCV. Experimental Data for Run 72............ 223 XCVI. Experimental Data for Run 7 3 ........ 224 XCVII.. Experimental Data for Run 74............ 225 XCVIII. Iodimetric Determination.-of. Bromoace.tone. . . . 228 ' xvi TABLE PAGE XCIX. Experimental Data for Run 7 5 ............ 24l( - C. Experimental Data for Run 7 6 ............ 242 Cl. Experimental Data for Run 7 7 ............ 248 CII. Rate of Reaction in Various Solvents . . . 251 CIII. Experimental Data for Run 7 8 ............ 260 CIV. Solubility of Salts in Methyl Acetate . . 264 ( CV. Quantitative Competitive Reactions .... 270 ! LIST OP FIGURES FIGURE PAGE ' 1. Blank Corrections at Varying Hydrogen Chloride Concentrations 21 ; 2. Data for Runs 3 and 4 Plotted for First Order Kinetics :57 : 3. Plot of Data of Runs 4, 10, and 15, Showing : Effect of Solvent on Rate 61 1 4. Data for Runs 13 and 14 Plotted for First Order Kinetics . ........... 62 5. Data for Runs 10, 21, and 23, Showing Effect of Added Substances on Rate ............ 63 6. Data for Runs 10, 16, and 17, Showing Effect of Varying Acetone Concentration on Rate . 64 7. Effect of Initial Acetone Concentration on ' First Order Rate Constant in Methyl Acetate 101 1 8. Arrhenius Plots' 129 : 9. Data of Run 35 Plotted for First Order Kinetics l4l : 10. Data of Run 45 Plotted for Second Order ; I Kinetics ................ ....... 143 11. Data of Run 49 Plotted for First and Second 1 Order Kinetics ..... 144 j 12. Data of Runs 51 and 52 Plotted for First Or- xviii FIGURE PAGE ; der Kinetics........................... 149 13. Data of Run 70 Plotted for First and Second Order Kinetics........................ . 155 14. Data of Run 71 Plotted for Second Order Kinetics . . ......................... 156 15. Plot of Data of Rim 7 4 .................... 222 16. Data of Run 75 Plotted for First Order Kinetics ......................... 243 17. Data of Run 76 Plotted for First Order Kinetics......... 244 18. Data of Run 78 Plotted for First and Second Order Kinetics ................... 26l CHAPTER I INTRODUCTION ' The reactions of 2,4-dinitrobenzenesulfenyl chlo- ride, bromide and thiocyanate with acetone (equation 1) are formally related to the analogous reactions of chlo rine, bromine and iodine with this ketone (equation 2). Because the latter reaction is one of the best studied cases in all of organic chemistry, the possibly similar but far less known reactions of equation 1 were selected - — for comparative purposes — as one of the first in a series of studies concerned with the mechanisms of re actions of sulfenyl halides with various classes of organic compounds. 1. CH^COCH^ + RSX = RSCH2COCH3 + HX X = Cl, Br, SCN 2? CE^COCH^ + X:X = XCH2C0CH3 + HX X * Cl, Br, I It has been shown in such studies as those of Rice and Kilpatrick,^ Dawson and Spivey,1^ and Rice and 45 Fryling that the acid catalyzed reactions of acetone with chlorine, bromine, or iodine in aqueous solution proceed at rates which are independent of the concentra tion or nature of th;e halogen, and which depend, in a first order manner, ubon the concentrations of acetone _____ 2 and acid present. The reaction is formulated as proceed ing by way of two steps: the rate controlling acid catalyzed enolization of acetone followed by the very rapid reaction of the enol with halogen. Almost no kinetic studies have been made of this reaction in non-aqueous solvents, presumably because the halogen acids produced in the reaction are extremely powerful acid catalysts in such solvents. The only systematic study was that of Cathcart1^ who found that in such solvents as ethylene chloride, carbon tetrachloride, ethyl acetate, etc., the reaction was quite rapid — being complete within a matter of minutes — and was auto- catalytic to an extreme degree. A related study in which the difficulties engendered by the production of hydrogen halide were avoided was that 6 of Bell and Tantram who studied the halogenation of ace tone by N-halogen compounds in chlorobenzene solution. They found that the reaction was of intermediate order, and interpreted their results on the basis of the same mechanism as postulated for the reaction in aqueous solu tion, assuming that the two steps, in chlorobenzene, are of comparable rate. In terms of actual rates, this means that the addition of halogen to the enol must be con siderably slower in this case, as the rate of enolization calculated by them from their data is almost identical____ 3 to the observed rate of enolization in water.. A similar situation, intermediate kinetics interpreted on the basis of comparable rates for the enolization and halogenation /TQ steps, was found in the paper by Zucker and Hammett on the iodination of acetone in sulfuric acid-water mixtures. They found that as the percentage of sulfuric acid in the solvent was increased, the rate of enolization increased greatly relative to the rate of halogenation. In view of the above, kinetic studies of the re actions of sulfenyl halides with acetone were planned in order to ascertain whether this reaction paralleled the halogenation reaction — and therefore had a similar mechanism. If the kinetics of the reactions of the sulfenyl halides did not parallel those of the halogens, the investigation was to be extended to elucidate, insofar as possible, the actual detailed nature of the reactions. CHAPTER II THE QUANTITATIVE DETERMINATION OP SUIPENYL HALIDES I. INTRODUCTION A method for the quantitative determination of sulfenyl halides was a necessary prerequisite to any kinetic study of the reactions of these substances. While considerable information concerning the reactions and properties of sulfenyl halides is available in the litera- ture, almost no quantitative work has been done. Bohme Q and Schneider-' have reported a single determination, wherein benzenesulfenyl chloride, in carbon tetrachloride solution, reacted quantitatively with aqueous potassium iodide according to the following reaction: C6H5SC1 + 2 I" = C6H5SSC6H5 + I2 + 2 Cl" The iodine was determined by titration with standard sodium thiosulfate in the usual manner. The only other report in the literature on the de termination of sulfenyl halides or their derivatives is 21 by Foss, who developed a method for determining certain sulfenamides and sulfenyl thiocyanates by their inter action with thiosulfate ions, and measurement of the unreacted thiosulfate. . : _ 5 II. DISCUSSION The methods of Itohme and Schneider^ and of Foss,21 together with several variations of them, were attempted, using 2,4-dinitrobenzenesulfenyl chloride (i). In no case was the amount of -iodine found greater than ninety- three hundredths equivalent per mole of I used. The work of Steelink"^ indicated that sulfite ion might be expected to react quantitatively with sulfenyl halides. Therefore, attempts to titrate I with standard sodium sulfite solution were made, but the results were unsatisfactory. Elimination of other possible sources of error in determinations patterned on the method of Bohme and Schneider suggested that water might be interfering. This proved to be the case, since satisfactory titrations of I (accurate to ± 1%) resulted when dry acetic acid (or acetic acid mixed with solvents such as ethylene dichlo ride) was employed as the reaction medium. Table III summarizes the results obtained in various anhydrous media The chief sources of error appear to be the pre sence of water in the reaction mixture and impurities in the sulfenyl halide. Since the presence of water (pre vious to the addition of the potassium iodide solution) leads to low results, all reagents must be dried before ----------------------------: ---------------------------- 5— use. Considerable error may also occur due to oxidation of iodide to iodine by oxygen of the air — which occurs chiefly during the time the solution is anhydrous — and it is necessary to carry out a blank with each set of de terminations to correct for the iodine so released. It was found that, other factors being kept constant, the magnitude of the blank depended-upon the partial pressure of oxygen in the acetic acid used — as is strongly indi- * cated by the closeness to which the observed Y factor (see experimental) approaches the expected value of 0.20. The amount of the blank was diminished considerably by sweeping the solvents with dry nitrogen before use. This indicated that the oxygen is merely dissolved, or loosely bound, and is not strongly complexed or combined with the sulfenyl halide or solvent. Moreover, the con stancy (with the exception of the 2-nitrobenzenesulfenyl chloride case) of the amount of X value (see experimental) due to oxygen, indicates that the limiting factor is the time allowed for the oxygen and sodium iodide to -react in 17 the anhydrous media. The data of Falciola, who reports the solubility of oxygen in acetic acid to be 0.164 moles * The Y factor represents the fraction of iodine re leased by.air as compared to that released by pure oxygen at 1 atm. The value X, mentioned below, is the amount of iodine released by oxidation other than that caused by the sulfenyl halide. ______________________________ ____________ , . 7 per liter, is in accord with this observation. For ex ample, the twenty-five milliliters of acetic acid used in the 2-nitro-4-carboxybenzenesulfenyl chloride case should contain 0.0041 moles of oxygen, whereas the X value is only 0.00028 equivalents of iodine. Were the amount of oxygen the limiting factor, one would expect 4 x 0.0041 = 0.0164 equivalents, according to the equation: 02 + 4 H+ + 4 I" = 2 H o + 2 I2. The effect of hydrogen chloride concentration on the blanks was also determined, since this substance is a product in the ketone-sulfenyl chloride reaction to be studied. When acetic acid, saturated with air, was used in these determinations, the blanks increased with in creasing hydrogen chloride concentration; while with nitro gen swept acetic acid, the magnitude of the blank was not appreciably altered by changes in the amount of hydrogen 4q chloride present. This is in accord with the known J acid catalysis of the reaction of iodide with oxygen. It was found that other sulfenyl halides of struc ture similar to that of I titrate satisfactorily by this method. A summary of the compounds tested and results ob- tained is given in Table VI. Triphenylmethanesulfenyl chloride cannot be titrated satisfactorily by this method; the release of iodine under the conditions used~is very ■ a slow and apparently Incomplete. Qualitative tests indicate that a similar case occurs with -1-anthraquinonesulfenyl t / chloride. The validity of this iodometric method of analysis in the.presence of certain substances of the type likely to be encountered in these studies was shown (Table VTII). No doubt, interference may be-anticipated from substances which oxidize iodide ion readily, or which interact rapidly with iodine, but only two such cases (bromoacetone and ordinary, stock cyclohexene) were encountered in the pre sent study. To ascertain whether the accuracy of this method of analysis is dependent upon the amount of sulfenyl halide used, varying amounts of I (Table IX) were deter mined. It may be noted that, in those cases where a very small amount of I was used, the results were consistently high. This may be caused by the fact that the blank cor rection in these cases is a large fraction of the total iodine released, and, consequently, an error in the blank (e.g. a low blank value) would lead to high results. III. EXPERIMENTAL 1. Preparation of Reagents. a. 2,4-Pinitrobenzenesulfenyl Chloride. The pr_oAuct„_ofL-V:ers-atile. Chemicals was recrystallized several 9 times from carbon tetrachloride. In later experiments, the sulfenyl chloride was prepared by chlorinolysis, by the* method of Assony,^ of bis-(2,4-dinitrophenyl) disulfide. In all cases the solution of I was decolorized with char coal during the first recrystallization. b. 2,4-Dinitrobenzenesulfenyl bromide (II) was prepared by a modification of the method of Swidler,^ A typical preparation of this substance follows: To a -solution of 5*1 g* I in 66 ml. of ice cold ethylene chlo ride (in an ice bath) 5.55 g. of aluminum bromide was added all at once, and the flask was swirled vigorously. The dark red solution was kept cold for fourteen minutes with occasional swirling. Absolute ethanol (ca. 3-4 ml.) was added slowly (caution), the solution was shaken with excess water, and the organic layer separated and con centrated to about 3 ml. (aspirator, steam bath). About 50 ml. of "Skellysolve A” was added, and the precipitated II* 5.0 g., (yield 83$) of yellow-orange solid, m.p. 103-5°, was collected. Recrystallization from carbon tetrachloride (with about 5 per cent benzene added) raised the melting point to 104-5°. It was found that the pre sence of a small amount of benzene, used either with the Skellysolve or carbon tetrachloride results in a product having better crystalline form. __________ o_2J4.=Dlnitrobenzenesulf.en.y_l__thiocyanate_(XII,),. , 10 In a typical preparation of this substance: To 11.95 g. of I in 160 ml. of benzene, in a glass stoppered flask, was added 21.25 g* potassium.thiocyanate and'2 ml. of distilled water. The mixture was shaken for about .fifteen minutes, filtered, and the solvent evaporated, using steam and an aspirator. Care was taken to stop the heating (and allow the solution to cool) before the last of the benzene was removed, since overheating decomposed the product. The pale yellow solid (or oil) was recrystallized from carbon tetrachloride, yielding.yellow crystals, m.p. 83-4°, - The yield depended on the number of recrystallizations needed to obtain a satisfactory crystalline product of . suitable melting point, since about, 20 to 60 per cent of the product was lost on each recrystallization. If seed crystals were available, the crystalline product., m.p. 83-4°, could be obtained with, one crystallization; if not, it often required three or four recrystallizations from carbon tetrachloride to produce a product melting.above 28 eighty-degrees. Recent work indicates that if methylene chloride is used in place of both the. benzene and the carbon tetrachloride used above, most.of these difficulties are•circumvented and better yields obtained (although a less distinctly crystalline product is obtained). d. 2-Nitrobenzenesulfenyl chloride (IV). This _^ukaianfifi_Maa-;P-iie^aredJ3yLJ^he_^iethpd^_d^qrib_ed in Organic, 11 Q Syntheses. fi* 2* 4-Dinitrobenzenesulfenyl acetate (V). The author is indebted to A. J. Havlik for this compound. Its preparation and purification are described in reference 25, _f. 2-Nitro-4-carboxybenzenesulfenyl chloride (VI). This was obtained similarly as V. S . * Carbon tetrachloride and ethylene chloride. The commercial solvents were distilled, retaining only the constant boiling and clear middle fraction. h. Acetic acid. Commercial glacial acetic acid (Baker Chemical Co.) was refluxed about three hours with three times the amount of acetic anhydride required to react with the maximum water present. The acid was then distilled, only the constant boiling middle fraction being retained. Sodium iodide. Baker’s analyzed sodium iodides was dried in an oven at 110° for at least one hour before use. iL* Starch indicator solution. This was prepared 15 according to the method of Crowell. ^ In later experiments it was prepared using water saturated with sodium chloride in order to prevent the destruction of the starch by bacteria. k. Potassium iodide solution. This was prepared by dlssolving_ab.out__8.5_g^_Ba,ker-Ls—analy-zed-potas.s-i-um------ 12 iodide in one liter of distilled water. 1 _ . Sodium thiosulfate. Standard sodium thio- sulfate solution (ca. 0.1 N) was prepared by the method 15 of Crowell, standardized using analytical grade potas sium iodate, and its normality checked by reaction with oven-dried analytical grade potassium dichromate. m. Sodium sulfite. Sodium sulfite solution, about tenth normal, was prepared by dissolving the required amount of Baker’s analyzed sodium sulfite in distilled water. The solution was standardized against standard iodine solution. n. Triphenylmethanesulfenyl chloride. The sample; used was obtained from P. S. Magee, prepared by the method 6? of Vorlander and Mittag, and was recrystallized from benzene before use. £• Iodine. Standard iodine solution was prepared by dissolving resublimed iodine in 0.5 N potassium iodide solution, and standardizing against the sodium thiosulfate solution. 2.* Oxygen. Oxygen gas was used directly from the cylinder, supplied by Linde Air Products Co. Hydrogen chloride in ethylene chloride. A solution of hydrogen chloride in ethylene chloride was prepared by passing hydrogen chloride (dried by bubbling r through a sulfuric acid drying tower) into ethylene_______ 13.. chloride. The solution was standardized by titrating a 25 ml. aliquot (mixed with excess distilled water) with standard sodium hydroxide solution, using pheholphthalein as indicator. Vigorous mixing was required near the end point;to extract all the hydrogen chloride into the aqueous phase. Twenty-five milliliters of the ethylene chloride solution required 3-75 ml. of 1.00 N base, in dicating 0.15 moles of hydrogen chloride per liter of ethylene chloride solution. £• Hydrogen chloride in acetic acid. This was „ prepared by bubbling dried (as in g, above) hydrogen chloride gas into dry acetic acid. It was standardized with 0.112 N sodium acetate in acetic acid (prepared by dissolving 2.3139 g. of oven-dried sodium acetate in 250.0 ml. glacial acetic acid in a volumetric flask) using brom-phenol blue as indicator. Three 3 ml. aliquots of the hydrogen chloride solution were titrated, requiring 7.0, 7-2 and 7*2 ml., respectively; Ave. = 7*1 ml.; N = 0.27. £. Methyl acetate. The preparation and purifi cation of this material is discussed in Chapter IV. 2. Titrations Using Aqueous Reaction Media. a. In each case, a standard solution of I was prepared by weigh ing out the desired amount into a glass stoppered flask 14 and pipetting in an accurately measured volume of carbon tetrachloride or ethylene chloride. Aliquots (10.0 ml.) of this solution were added to the titration mixtures (in glass stoppered flasks) listed in Table I, and the result ing mixture vigorously shaken for two to three minutes. Excess standard sodium thiosulfate solution was added from a buret, the solution again shaken, 2 ml. of starch indi cator solution added, and the excess thiosulfate titrated with standard iodine solution. The results of different variations of this method are shown in Table I. b. To a known solution of I in ethylene chloride, in a glass stoppered erlenmeyer flask, was added excess standard sodium sulfite solution. The flask was stoppered and shaken vigorously, excess potassium iodide solution was added, and the excess sodium sulfite titrated with standard iodine solution. The results are summarized in Table II. 3* Titrations Involving Anhydrous Reaction Media. A standard solution of I was prepared, as in.(2) above, using; ethylene chloride as solvent, and 10 ml. aliquots of this were added to the reaction media (contained in glass stoppered erlenmeyer flasks) described in Table III. . After ninety seconds, during which time the flask was swirled gently about four or five times, about 40 ml. of 15 TABLE I TITRATIONS USING AQUEOUS REACTION MEDIA Equiv. ArSCl* Present Method of Titration Equiv. Iodine Pound $ • 1. .00082 used 40 ml. 0.05 M KI .00072 88.0 2* .00082 same as 1 .000716 87.4 3. .001094 used 40 ml. 1 M KI .000935 85.5 4. .001094 used 7.55 g. solid KI and 1 ml. water .000940 85.8 5. .001094 Added I to mix of 7.3 g. KI with 90$ of theor. am’t of thiosulfate soln. .00954 87.0 6. .002328 used 25 ml. 1 M KI soln. .00214 91.9 7. .002328 same as 6 .00215 92.3 8. .002328 same as 6 .00210 90.0 9. .002328- same as 6 with 0.5 ml. 6 N H2S04 added .00214 91.9 10. .001377 first added excess thio., then 20 ml. 1 M KI .00124 90.5 11. .001377 same as 10 .00123 89.5 12. .000934 same as 6- .000856 91.8 13. .000934 same as 3 .000851 91.3 14. .00338 Added 2.5 g. KI: after 3 min. added excess thiosulfate .00315 93.1 * Ar = 2,4-dinitrophenyl. 16 TABLE II TITRATIONS USING SODIUM SULFITE * Equiv. ArSCl Present Equiv.** Iodine Found $ ! 1. .00278 .00101 36.3 . 2 . . . , .00288 .00115 40.0 * These titrations were carried out by shaking a known amount of sulfenyl chloride, in ethylene chloride, with a known solution of sodium sulfite. The excess sulfite w&s estimated by iodimetric titration. .** In each case considerably more iodine was released after the titration was complete, indicating that un reacted sulfenyl halide was present. 17 TABLE III TITRATIONS USING ANHYDROUS REACTION MEDIA Eqniv. 'ArSCl Present Reaction Media Equiv. - ! Iodine Pound $ 1 . .000934 30 ml. ethyl ether sat. with Cdl2 .000908 97.3 2. .000934 same as 1 .000904 96.9 3. .001170 50 ml. ahs. ether sat. with Cdl2 none 4. .001170 50 ml. ahs. ether and 3 ml. 57$ HI .001040 89.0 5. .001170 25 ml. abs. ether, 25 ml. HOAc, 4 g. Nal .001172 100.2 6. .001170 same as 5 .001166 99.7 7. .00812 40 ml. C2H4C12, 15 ml. HOAc, 4 g. Nal .000803 98.8 S. .000812 same as 7 .000804 99.0 9. .000812 20 ml. C2H4C12, 15 ml. HOAc, 4 g. Nal .000811 99.9 o H .001532 same as 9 .001527 99.5 n. .001532 same as 9 .001529 99.6 12. .001.532 , same, as 9 . .001,524 99.3 I8— 0.5 N potassium iodide and 60 ml. of distilled water were added, and the mixture was shaken vigorously. Excess standard sodium thiosulfate solution was then added (with swirling) from a buret, the flask was restoppered and vigorously shaken, 2 ml. starch indicator solution was added, and the excess thiosulfate determined with standard iodine solution. After the end-point was reached, it was desirable to add an extra drop or two of iodine solution, restopper the flask and shake again. If the color dis appeared, a new end point was obtained. This redetermina tion of the end point was necessary in about one-twentieth of the titrations performed, and was probably caused by trapping of some of the thiosulfate solution beneath the ethylene chloride phase. It was later found that if the sulfenyl halide was dissolved in glacial acetic acid, or some other water-miscible solvent, the ethylene chloride could be omitted entirely and the titration carried out in a one phase system without requiring vigorous shaking. The results obtained in this manner appear to be somewhat less erratic than those from the two-phase titrations. The use of the aqueous potassiun iodide solution was also found to be unnecessary and it may be replaced by water. If, however, an organic solvent (e.g. ether or benzene) of density lower than water is present, it was found advisable to add (after the water had been Introduced) sufficient - = r 9 — carbon tetrachloride or ethylene chloride to make the organic phase more dense than water. This avoided the troublesome operation of titrating through the organic phase. 4. Blank Determinations. a. Determinations without added hydrogen chloride. These determinations were carried out exactly as described in (3)j above, except that no sulfenyl halide was added. The amounts of iodine found varied from about 0.010 to 0.030 milliequivalents, depending upon the reagents used. ' The values of the blanks thus obtained have been subtracted from all titration values reported in this paper except where blank values obtained as in (b) below were appro priate. b. Determinations with added hydrogen chloride and using air-saturated acetic acid. These determinations were carried out as in a, above, except that varying amounts of a standard solution of hydrogen chloride in ethylene chloride (see l-£ above) were mixed together with the ethylene chloride and acetic acid. The results are shown in Table IV and Pig. I. All titrations in which hydrogen chloride was present, with the exception of those employing acetic acid preswept with nitrogen, have been corrected accordingly. Since the value of the blank 20 TABLE IY BLANK DETERMINATIONS USING ADDED HYDROGEN CHLORIDE i V AND ACETIC ACID SATURATED WITH AIR Equiv.f HC1 Eqniv. I£ Present Eonnd ylOi^_____________xlO^ 1. Oi| 2.90 2. 0.0* 2.49 3. 1.6; 3.13 4. 3.8l 5.11 5. 6.8. 6.93 6. 7*3 5.98 7. 8.6 5.88 in :o , ; x •o C 3 o C M H 10 11 12 Equiv. HC1 Present x 10 _______ EIGUEE.J_______ 22 correction varies with the reagents used, it was necessary to repeat the blank determination each time a new set of reagents was prepared, and even with the same set if it was usdd over a considerable period of time. It was as sumed that the variation of the blank correction with changes in hydrogen chloride concentration would be ap proximately the same in all these cases, and therefore blank corrections (when hydrogen chloride was present) were read from curves drawn parallel to the one shown in Fig. I. This simplification required only the initial point (at hydrogen chloride concentration equal zero) to be determined experimentally. S . ' Determination of blanks using added hydrogen chloride and nitrogen-swept acetic acid. About five or six grams of oven-dried sodium iodide, dried at 120°, was placed in a similarly dried 250 ml. glass stoppered erlen meyer flask 1 In rapid succession there was then added, 20 ml. glacial acetic acid (previously swept for thirty minutes with dry nitrogen), 10 ml. of pure, dry methyl acetate, and varying amounts of the acetic acid solution of hydrogen chloride (see 1-q above). The stopper was replaced and the mixture allowed to stand for ninety seconds, during which time it was swirled gently four or five times. The flask was opened, 110 ml. distilled water 23 was added, and the resulting solution titrated as above. The results are given in Table V. The average of these titrations (omitting point 5) is 0.023 railliequivalents of iodine. This value does not differ significantly from those obtained for the blank in which hydrogen chloride was absent. It should be noted that an error of one drop — 0.05 ml. of 0.1059 N sodium thiosulfate solution — in the titration would cause an error of 0.005 milliequival- ents of iodine. 5* Titrations of Sulfenyl Halides Other Than I _ . Standard solutions of the sulfenyl halides in acetic acid were prepared as described in (2-a) above. These solu tions were titrated by the procedure described in (3) above. The results are given in Table VI. 6* The Effect of Dissolved Oxygen on the Determina tion of Sulfenyl Halides. In the determinations to ascer tain this effect, the sulfenyl halide was dissolved in glacial acetic acid, treated as noted in Table VII, and then sodium iodide was added and the mixture was titrated in the usual manner. The results obtained are shown in Table VII. The values of iodine found are not corrected for any blank. The value X is the amount by which the iodine found was greater than the expected value. The -value_Y_is—the_X_value—for—air-^s at urat-ed-solut ion-minus--- 24 TABLE V BLANK DETERMINATIONS USING- ADDED HYDROGEN CHLORIDE AND NITROGEN-SWEPT ACETIC ACID UNDER THE TYPIQAL CONDITIONS USED IN THE SULFENYL HALIDE DETERMINATION . . . Determination Meq. HCl Added Meq. Iodine Pound 1 0 0.018 2 0 0.022 3 1.04 0.025 4 2.49 0.017 5 2.40 0.060 6 1.74 0.019 7 2.08 0.039 8 2.40 0.015 9 1.98 0.030 25 TABLE YI TITRATION OF OTHER I SULFENYL HALIDES Sulfenyl Halide Used Equiv. of Sulfenyl Halide Equiv. of Iodine Found f o 1., ArSBr* .00232 .00231 99.5 2. ArSBr .001508, .001520 100.6 3. ArSBr .0008197 .0008260 100.8 4. ArSBr .0008197 .0008216 100.2 5. ArSBr .0008197 .0008215 100.2 6. ArSBr .0008197 .0008191 99.9 7. ArSBr .0008197 .0008245 100.6 8. ArSSCN .000737 .000748 101.3 9. ArSSCN .000737 .000728 98.8 • o H ArSSCN .0005911 .0005945 100.6 11. ArSSCN .000737 .000734 99.4 12. ArSSCN. .0005911 .0005976 101.1 13. ArSSCN .0005911 .0005889 99.6 14. ArSSCN .0005911 .0005887 .99.6 15. ArSOAc** .0004763 .0004861 102.0 16.. ArSOAc** .0004763 .0004948 103.7 17. ArSOAc .0006071 .0006264 103.2 18. ArSOAc .0006071 .0005847 96.2 2 6 TABLE VI (CONTINUED) TITRATION OP OTHER SULFENYL HALIDES Sulfenyl Halide Used Equiv. of Sulfenyl Halide Equiv. of Iodine' Found 1 o 19. ArSOAc .0006071 .0005800 95.5 20. Ar * SCI *** .0004649 .0004604 99.1 21. Ar'SCl .0004649 .0004696 101.0 22. Ar'SCl .0005464 .0005465 100.0 23. Ar* SCI .0005464 .0005517 100.9 24. o-no2c6h4sci .001236 .001222 98.9 25. o-no2c6h4sci .001242 .001238 99.5 26. o-no2c6h4sci .0011899 .001196 100.4 27. o"N02C6H4SC1 .0007827 .000786 100.8 28. o-no2c6h4sci .0009947 .0010025 100.9 29. o-no2c6h4sci .001734 .001700 98.0 30. o-no2c6h4sci .001734 .001716 98.9 31. (C6H5)5C-SC1 .000598 .000186 31.1 32. (c6h5)3c-sci .000598 .000432 72 4 **** 33. (c6h5)3c-sci .000598 .000585 g t - j g ***** Ar = 2,4-dinitrophenyl ** Dry nitrogen was bubbled through the solution of the sample before titration. *** Arf = 2-Nitro 4-Carboxyphenyl **** Swirled four minutes before aqueous solution added. . ***** swirled eight minutes before aqueous solution added.; 27 TABLE YII THE EFFECT OF DISSOLVED OXYGEN Theory Meq. Found Meq. X Vol. HOAc Treatment 2,4-Dinitrobenzenesulfenyl Chloride 1.5551 1.6185. 1.5551 1.5776 1.5551 1.8456 1.5551 1.5779 .0634 20 .0225 20 .2905 20 .0228 20 Y 0.15 2-Nitro. 4-Carboxybenzenesulfenyl Chloride; None (saturated with air) Np for 20 min. Op for 5 min. Op for 5 min., then Np for 15 min. 0.4649 0.5332 0.4649 0.4725 0.4649 0.7477 0.4649 0.4817 0.5464 0.5586 0.5464 0.5638 .0683 25 .0076 25 .2828 25 .0168 25 Y 0.22 .0122 50 .0174 50 None (saturated with air) Np for 15 min. Op for 5 min. Op for 5 min., stand for 10 min., Np for 15 min. Np for 15 min. Op for 5 min., stand for 5 hr., Np for 15 min. 2.4-Dinitrobenzenesulfenyl Acetate: .0445 50 0.6071 0.6516 0.6071 0.5977 -.0094**50 0.6071 0.8894 .2823 50 0.6071 0.5926 -.0055**50 Y 0.18 None (saturated with air) Np for 10 min. Op for 5 min. 02 for 5 min., stand 1 hr., Np for 15 min. 28 TABLE VII (CONTINUED) THE EEEECT OP DISSOLVED OXYGEN Theory ■ Meq. Pound* Meq.- X Vol. HOAc (ml.) Treatment 2-Nitrobenzenesulfenyl Chloride: 1.7341 1.7127 -.0214** 20 N2 for 15 min. 1.7341 1.7410 .0069 20 Air for 20 min. 1.7341 1.8549 .1208 Y 0.20 20 O2 for 5 min. * No Blank correction has "been made. The negative value probably signifies that the amount of impurity in the sulfenyl halide was greater than the blank value for the sample treated with nitrogen. 29 the X value for nitrogen-swept solution, all divided by the X value for oxygen-saturated solution minus the X value for the nitrogen-swept solution. If the magnitude of the titration increase due to dissolved oxygen is proportional to the partial pressure of oxygen, then this ratio Y should be the same as the partial pressure of oxygen in air divided by the pressure of pure oxygen used (l atm.), which is approximately 0.20. The gases used were dried by passing them through a sulfuric acid drying tower. 7* Titrations of Sulfenyl Halides in the Presence of Substances Capable of Possible Interference. These deter minations were carried out using I and by the procedure described in (3) above, except that — after swirling the anhydrous mixture for about one minute — three milliliters (or two grams if a solid) of the substance being tested was added, the mixture swirled one minute more, and the titration completed in the usual manner. The results are given in Table VIII. The substances used were purified by distillation, if.liquids; and by recrystallization from absolute ethanol if solids. All are well known compounds (A, B, C, D, E, K, M) or have been reported in the litera- lio 33 33 \ ture (G, H, 1, J~^) with the exception of substance P which has not been reported previously. It was prepared 30 TABLE VIII DETERMINATION OP I IN THE PRESENCE OP OTHER SUBSTANCES Substance Tested f o I- Pound- A. 2-Pentene 100. 4 B. Ethanol (anhydrous) 99.6 C. Dimethylaniline 99.6* D. Benzyl Alcohol 99.9 E. Acetoaeetic Ester 99.4** P. CH^COCHC SAr)C00C2H^*** 100.8- G. 2-Chlorocyclohexyl 2,4-dinitrophenyl sulfide 99.3 H. C6H5CHClCH2SAr 100.2 I. ArS0C2H5 101.33 J. CH5COCH2SAr 100.3 K. Acetone 99.1 L. Acetone 101.7 M. 99.3 * When dimethylaniline was added to.the titration mixture it turned into an almost solid slush. When the aqueous KI ■was added, and the mixture shaken, almost no iodine was observed in the aqueous layer although in a normal titra tion almost all of the iodine goes into the aqueous phase .at this point. Nevertheless the solution titrated satis factorily. Apparently an addition complex between di methylaniline and iodine is formed, but is decomposed completely by the thiosulfate solution added. 31 TABLE VIII (CONTINUED) DETERMINATION OP I IN THE PRESENCE OP OTHER SUBSTANCES Substance Tested $ I Pound , The presence of aeetoacetic ester seems to make the titration more difficult — causing the iodine to remain in the ethylene diehloride layer, and making the end point less distinct. *** Ar = 2,4-dinitrophenyl. **** An anhydrous solution of HC1 gas in ethylene di chloride containing .000635 equivalents of HC1 was used. 32 in good yield from I and ethyl acetoacetate by mixing and allowing the solution to stand at room temperature until it gave no color when a small portion of it was shaken with potassium iodide solution containing starch indi cator. The compound was recrystallized from absolute ethanol; fine yellow needles, m.p. 112-3°. Analysis (by J. V. Pirie): Calc, for c12Hi2N2°7S: C> H> 3*69* Pound: C, 44.12; H, 3.81. When ordinary stock cyclohexene was used, the titration values were from 150 to 250 per cent high, on the basis of the amounts of I known to be present. A blank determination showed that this was undoubtedly caused by oxidant impurities in the olefin. Bromoacetone (one of the products obtained in reaction of II with acetone (see Chapter V) also led to high results in the titration of II. Separate titration (see Chapter v) showed that this was due to release of iodine by interaction of bromo acetone and sodium iodide under the conditions of the titration. 8. Determination of Varying Amounts of 1. The de sired amounts of I were weighed directly into glass stoppered erlenmeyer flasks and dissolved in about 20 ml. of ethylene dichloride. Fifteen to twenty milliliters of acetic acid and about four grams of sodium iodide were 33 then added, and the titration completed as described in (3) above. The results are summarized in Table IX. 34 TABLE IX TITRATION OP DIFFERENT AMOUNTS H o Equiv. ArSCl Used Equiv. Ip Foiand. 1 o ...... 1. .000317 .000323 101.8 2. .0003325 .0003362 101.0 3. .000333 .000365 106.5 4. .000342 .000345 100.9 5. .0006255 .0006204 99.1 6. .0008268 .000861 104.0 7. .0009351 .0009295 99.2 8. .001021 .001029 100.4 9. .001151 .001154 100.2 10. .001152 .001155 100.2 11 « .001365 .001350 98.9 12. .001367 .001303 ' 99.8 13. .001721 .001687 97.9 14. .001955 .001961 100.2 15. .002021 .002013 99.5 16. .002528 .002540 100.2 17. .003039 .002900 95.5 18. .004473 .004465 99.9 19. .007611 .007641 100.3 20. .01002 .00985.... 98.3 CHAPTER III THE REACTION OF 2,4-DINITROBENZENESULFENYL CHLORIDE WITH ACETONE I. INTRODUCTION Zincke and coworkers ^3 were the first to study the reactions of certain aromatic sulfenyl chlorides with such ketones as acetone and acetophenone. The formation of hydrogen chloride was noted and the solid products obtained were formulated as beta-keto sulfides. The work of Fries and coworkers on similar reactions has also been noted in a recent review (1) RCOCH^ + ArSCl = RCOCHgSAr + HC1 35 Kharasch, Wehrmeister and Tigerman-'-' reported the similar reaction (equation l) of I with acetone and acetophenone and also formulated the products as beta- keto sulfides. They reported "a good yield" of the acetone product and a 95 pe** cent (crude) yield in the q S T case of acetophenone. Recently McQuarrie has extended the reaction with I to a considerable number of other ketones. II. DISCUSSION As a first step in the quantitative investigation ; ---------------------------------------------- 36' of the reaction of I with acetone, it was shown that the reaction (equation 1, R = CH^, Ar = 2,4-dinitrophenyl) was essentially complete (95 per cent isolated product) under conditions suitable for rate determinations. It also seemed desirable to independently confirm the structure of the product. Accordingly, an independent synthesis of 2,4-dinitrophenyl aeetonyl sulfide, from 2,4- dinitrothiophenol and bromoacetone, was effected. A syn thesis of 2,4-dinitrophenyl phenacyl sulfide from phenacyl bromide and 2,4-dinitrothiophenol was also carried out. Both compounds corresponded in melting points to those of the corresponding compounds prepared from I and the ketone^, and mixtures of the products gave no depression in melting point. As further evidence for the structure of the aeetonyl sulfide given above, the 2,4-dinitrophenylhydra- zone derivative was prepared. The possibility that the monosubstitution product might react further with I was also considered. From the nature of the product isolated, however,- no evidence for the formation of such a second product was noted, and ex periments designed to produce possible disubstitution pro ducts from I and the aeetonyl sulfide have not yielded such a product. That such a compound can be formed has 50 been shown by Schotte^ who reports the formation of c<. s<,di-(2.4-dinitrophenylthio) acetone from c* . ot1 37 dimercapto acetone and 2,4-dinitrochlorobenzene. By suitable analysis (see Chapter II) it was shown that the presence of small amounts of acetone, 2,4-dinitro- ■ phenyl aeetonyl sulfide, and hydrogen chloride do not in validate the titration for the sulfenyl chloride. It was also shown that the reaction was sufficiently slow, at ; room temperature in ethylene chloride, to follow by a titration technique. Preliminary rate studies were then carried out, using dilute solutions of I and acetone. When a solution of I (0.047 M) and acetone (0.094 M) in ethylene chloride was kept at constant temperature (26.5°C) and aliquot portions titrated for sulfenyl chloride content at regular time intervals, it was found that less than 2 per cent of the sulfenyl chloride had reacted after ten hours, and that, after one hundred six hours, 92 per cent of the sulfenyl chloride still remained. Similar results were obtained with acetic acid as solvent. In view of the nature of the reactants, it appeared that satisfactory kinetic data would not be obtainable over the extended periods of time which the above experi ments indicated would be necessary, and therefore that higher concentrations of reactants would be needed to increase the rate of reaction. Since the concentration of I is limited by its solubility (roughly four grams -per hundred milliliters of- ethylene-chloride, - and somewhat * .............. 3B less in acetic acid) it was necessary to increase the concentration of acetone disproportionately. When the acetone concentration was increased to about two and seven tenths molar (which corresponds to about twenty volume per cent acetone in the solution) it was found that the reaction was sufficiently rapid for convenient kinetic studies — the half life of the reac tion being about twenty-four hours. Exploratory studies, over short time intervals, showed that there was no sig nificant difference in the rate of reaction in ethylene chloride or acetic acid, and that the presence of anhydrous hydrogen chloride in either solvent affected the rate of reaction only slightly. It was also found that the rate was dependent upon the initial concentration of sulfenyl chloride. These facts indicated that the reaction between I and acetone was not analogous to the reaction of halogens with acetone, in which the rate of reaction is independent of the concentration of the halogen, and is decidedly sub ject to acid catalysis. More accurate rate runs, over longer time intervals, were then undertaken. When the titration data for these runs were corrected for the "blanks" (cf. Chapter II) it was found that the reaction was first order with respect to I. The results of runs 1-6 are shown in Tables XII through XVII. Er.om_these_dat_a_it„c.an_be_seenJ;hat_the____ 39 rate of the reaction is almost exactly the same in ethyl ene chloride as in- acetic acid, and that the presence of hydrogen chloride increased the rate only very slightly. The order of the reaction with respect to acetone in these runs could not be ascertained since the change in the concentration of acetone is negligible during a run. It can, however, be definitely stated that the enoliza- tion of acetone is not the rate determining step; I must be involved in the rate determining step, and hydrogen chloride is not. This is. almost exactly opposite to the results found for halogenation of acetone, in which the acid-eatalyzed enolization of the ketone is almost cer tainly the rate determining step. In these runs it was noted that the points obtained / the first day of the run and those obtained on the second day formed two separate parallel curves, with a curve of lesser slope, corresponding to a slower night rate, be tween them. Light was the most probable cause for such behavior, as the reaction mixture was exposed to ordinary diffuse light during the day, while at night it was in almost total darkness. Runs 7-12 were therefore made in black flasks, and it was found that this "overnight'’ de viation disappeared. Tables XVIII through XXIII show the results of these "dark" runs. However, when the .change to black flasks was made, a necessary change in 4D laboratory quarters and constant temperature apparatus was also made, so it was desirable to confirm this effect of light. Two runs (13 and 14) were set up simultaneously, using identical conditions and reagents, except that one was carried out in a transparent flask, while the other was in a black flask. -No significant difference was found (see Tables XXIV and XXV, and Pig. 4) in the rate con stants or rate curves obtained. It was therefore con cluded that the "slower night rate" was probably due to environmental factor(s) other than light* and that the light effect, if it exists at all, is smaller than the experimental error in these runs. The lack of a solvent effect inechanging from ethylene chloride to acetic acid in the above runs was * quite surprising. The question arose as to whether this was because the rate of the reaction was independent of solvent effects, or whether it was caused by preferential solvation by the large excess of acetone present. To clarify this matter, the reaction was run in a third solvent, carbon tetrachloride, chosen chiefly because its dielectric constant (2.24) differs greatly from those of The first six runs (in transparent flasks) were done in*a constant temperature bath set next to a window, and it may have been the cold night air which, by cooling the reaction flask slightly, caused the lower night rate. Ill either acetic acid (6.4) or ethylene chloride (10.5). The I results of this run (see Table XXVT) showed that change of solvent alters the rate of the reaction, but that the ef fect is not very large. All of the above rate runs utilized a large and constant excess of acetone, and for this reason the order of the reaction with .respect to acetone could not be de- 1 termined. Studies were therefore initiated in which the 1 concentration of acetone was varied systematically. As shown in Tables XXVII1 and XXVIII, it was found that chang- ■j ing the acetone concentration by a factor of two changed the observed rate constant in runs carried out in ethylene chloride by a factor jof approximately fivej and the effect was shown to be similar in acetic acid (Tables XXIX and XXX). If other facto'rs are not considered, this would • i correspond to an order of the reaction with respect to acetone of 2.3> and therefore a total order of the re- . * action of 3*3* Such an order is highly unlikely. Therefore it seemed most probable-.that the change of rate with acetone concentration was in large part influenced by the effect of the nature of the solvent — the latter being altered i considerably by addition of the highly polar acetone. v The effects of an added salt, of change in surface, and_of_possib.le_c.atalys±s_by_p^itoIuenesulfoni.c_ac.id_were__ 42 also tested: added lithium chloride exerted a marked positive effect on the rate in acetic acid (Table XXXI), b u f f c p-toluenesulfonic acid had no noticeable effect on the rate -- an observation which accorded with the earlier study of the effect of added hydrogen chloride. The lack of an effect by added‘glass surface was shown in a run using ethylene chloride as solvent. The effect of water is shown in Table XXXIV and Pig. 6. Curve A is for the run with water present, Curve B is a run carried out under similar conditions with water absent. These data suggest that water does not intrinsical ly affect the reaction of I with acetone- as such, but that an independent and competing reaction with I occurs, and that the resulting curve is the composite of the two re actions. The formation of an insoluble high-melting pro duct, probably bis-(2,4-dinitrophenyl) disulfide is in accord with this viewpoint, since this is known to be a product of the hydrolysis of I. Further attempts to catalyze the reaction were made. When I, (0.128 moles), acetone (0.025 moles) and aluminum chloride (0.0098 moles) in ethylene chloride were allowed to react at -3° for four hours (see experimental), 90 per cent of the sulfenyl chloride used was unchanged (shown by formation of the cyclohexene adduct). None of acetony-l—suif-ide—was—found-.— Mosb—likely,—the-^aluminurri- ■ : ~~~ chloride complexes preferentially with the acetone, and thus prevents, or at least does not catalyze the reaction with I. Attempts to find basic catalysts were also made. The choice of bases is very limited since the sulfenyl •34 halides are known'-' to react with almost all known basic substances. It was felt, however, that tertiary amines might be satisfactory and pyridine catalysis was attempted. However, when pyridine, I, and acetone were allowed to react (see experimental) both an insoluble product (pror? bably the disulfide) and the aeetonyl sulfide were obtained. It was also found that pyridine and I react even in the * absence of acetone to give this insoluble product. Tri- ethylamine was shown to behave similarly. Ultraviolet light was also shown to be unsatisfactory as a catalyst. Table X summarizes the rate data considered in this chapter. In attempting to interpret these data the following mechanisms may be considered. Mechanism A is based on the analogy of-the reaction of I plus acetone to the halogen-acetone reaction. ^This observation has been confirmed by Dr. L. Goodman^? of these laboratories, who has found evidence that the reaction observed is a pyridine catalyzed hydrolysis of I by traces of water present. The results of the pyridine-I reaction in sealed tubes (reported in Chap ter IV) are in accord with this hypothesis. 44 TABLE X SUMMARY OP RATE RUNS Temp.: 26.5° - . Run Sol vent * . Conditions Acetone Cone. CM) _ kl (hr.-1) Table No. 1. A Transparent Plaslc 2.710 .0277 XI 2. B Transparent Plask 2.741 .0278 XII 3. A Transparent Plask 2.711 .0276 XIII 4. B Transparent Plask 2.741 .0282 XIV 5. A Transparent Plask .and added HC1 2.711 .0290 XV 6. B Transparent Plask ,and added HC1 2.741 .0283 XVI ■ 7. A Opaque Plask 2.711 .0294 XVIII 8. A Opaque Plask 2.711 .0288 XIX 9. A Opaque Plask 2.711 .0273 ** XX 10. A Opaque Plask 2.711 .0293 XXI 11. A Opaque Plask 2.711 .0272 XXII 12. B Opaque Plask 2.741 .0265 XXIII 13. A Transparent Plask 2.711 .0287 XXIV 14. A ‘ Opaque Plask 2.711 .0292 XXV 15. C Opaque Plask 2.700 .0193 XXVI 16. A Opaque Plask 5.422 .1507 XXVII 17. A Opaque Plask 1.355- .00605 XXVIII 45 TABLE X (.CONTINUED)' SUMMARY OE RATE RUNS Temp.: 26.5° Run. Sol vent . Conditions Acetone Cone. ( I f f ) ' ki (hr.-1) Tahle No. 18. i B Opaque Plask 5.482 .1522 XXIX ■ 19 * B Opaque Plask 1.570 .00715 XXX 20. B Opaque Plask with LiCl Added 2.741 .0511 XXXI ; 2i. A Opaque Plask with added surface 2.711 .0295 XXXII 22. B Opaque Plask with added p-CH^CgH^SO 2.741 3H .0264 XXXIII 25. A Opaque Plask with water added 2.711 --- XXXIV • C \ J A. Opaque Plask 1.796*** .0049 XXXV . 25. A Opaque Plask 1.796*** .0040 XXXVI * • Solvent: A Ethylene Chloride B Acetic Acid C Carbon Tetrachloride ** Temperature control was poor during this run. *** Isopropenyl Acetate was used in place of acetone. ■ - ■ zfg- Possible Mechanism A: k, k0 CH^COCH^ + HA y~-— » CH3CCH3 4- A" CHgC«CHg.+ HA -1 OH -2 - OH' n r CH^C=0Ho + ArSCl ----- * CH,CCH0SAr - 9 - Cl 31 2 31/ 2 OH +OH k4 CHoCCH^SAr ------» CHoCOCH^SAr + HA 3 u 2 «— r p 3 2 OH -4 + For such a process, one can derive — • using the method 14 proposed by Christiansen — the following kinetic ex pression in which the protonated ketone, the enol form and the protonated aeetonyl sulfide are considered as the intermediates of low concentration and k_3 is set equal tquzero. -d(ArSCl) v k-jk^ (Acetone) (HA) (ArSCl) kgk^ (ArSCl) + (ArSCl) + k_^k_2('HA) Accepting this expression, the only way one can come to the observed result (that the acid concentration does not affect the rate) is to assume that k^ is very small in comparison to the other rate constants. This permits dropping of the first two terns in the denominator of the rate expression, for these become negligible in _ _ _ _ _ . 47 comparison with the third. When this is done, the acid concentration terms cancel out and leave the expression: -d (ArSCl) _ klk2k3 (Acetone) (ArSCl) — = ~ kohs (Acetone) (ArSCl) This is essentially the same as saying that the reaction proceeds by a two step mechanism, the first and rapid step being the enolization of acetone and the second (rate controlling) involving the reaction of I with the enol. As may be seen from the above kinetic expression, this would predict that the reaction kinetics should be first order with respect to acetone, whereas the observed order for acetone is 2.3. The difference would have to be explained by the solvation effects already referred to above. Although the rate of enolization of acetone is 6 13 probably faster * J than the observed rate of reaction, it was considered necessary to determine whether the re action between I and the enol form of acetone might be slow enough to be the rate determining step. For this purpose isopropenyl acetate (the enol acetate of acetone) was used. Preliminary tests indicated that this compound reacted with I at a rate comparable to that of acetone, but unfortunately no definite adduct could be obtained. In every attempt to isolate the product of this reaction only the aeetonyl sulfide and/or a red-brown tar could be obtained. This result is not too surprising if one con siders that the probable nature of the adduet is as shown below, and that such a structure is likely to be an un stable one. Nevertheless, rate studies were made for the re action of ArSCl and isopropenyl acetate. First order kinetics were found with respect to ArSCl (using a large excess of isopropenyl acetate). The results, given in as acetone. That the analytical method used in these studies is applicable in this case is shown by the fact that the results are fairly consistent, and that, after a sufficient reaction interval, a negative test for ArSCl is obtained, showing that reaction is complete and that none of the products releases iodine under the conditions of the titration. A second run (Table XXXVI) confirmed the order of magnitude of the rate — even though the precision was not as high as could be desired — a dif- ococ: ■ » CEUCOCHgSAr + CH^COd (?) Table XXXV, are that isopropenyl acetate, under strictly comparable conditions, reacts only about one-sixth as fast "49 ference of 20 per cent in values of the rate constant was found between the two runs. On the basis of relative enol content between iso propenyl acetate and acetone (known to have a very low concentration of enol^), the above result is indeed sur prising, and is therefore opposite to what would be ex pected if mechanism A were involved. The results with isopropenyl acetate do not, however, definitely exclude mechanism A, since one cannot a priori decide what effect the change from hydrogen to acetyl group on the oxygen of the enol would make in the rate, and there is again the need to consider the possible effect of the reaction systems involved • — for the solvent system ethylene chloride plus acetone is different from ethylene chloride plus isopropenyl acetate. In fact, the results are con sistent with mechanism A insofar as they support the as sumption that the addition of I to enol would be a slow step as compared to the rate of enolization. Another possible mechanism, in which the reaction is formulated as a termolecular process — involving two moles of acetone -- is as follows: 1 -ycr Possible Mechanism B: i i 0 H 2 CH3COCH3 - 9 - ArSCl » CH3CO-CH2 » CH^COCHgSAr (a) A - At Cl + (CH^gC^H Cl or CI^-C-CH- I I 9 P OSAr (b J 2 CH~COCH, + ArSCl --> CH,C-CH„---> CH,C=CH, 5 5 5 ii 2 5 d 9 Ar-S-Cl + (CH3)2C=9H Cl" That this is a possibility worthy of serious considera- tion is indicated by the work and calculations of Swain^ by which he presents evidence that many reactions which appear kinetically to be pseudo first order or second order are really termolecular processes. In fact, in one 57 paper ' he presents rather convincing evidence that the enolization of acetone is actually a termolecular process. involving the simultaneous action of a nucleophilic and an electrophilic agent on a molecule of acetone. In the reaction, as pictured above, a second molecule of acetone is acting as the nucleophilic reagent, and the sulfur atom of I is acting as the electrophilic agent, leading to either the observed product (a) or the enol " 51 sulfenic ester (b). The latter, In turn, could rearrange to (a). This mechanism would predict third order kinetics -- second order with respect to acetone and first order in I. This comes quite close to the observed kinetics, the difference being that the observed order for acetone was 2.3. This difference could be ascribed to the fact that changing the concentrations of acetone considerably alters the dielectric constant of the reaction medium. Prom the above results, it next appeared essential to ascertain the correct order with respect to acetone. Work towards this goal is described in the following chapters. III. EXPERIMENTAL* 1. Preparation of Reagents. a. Acetone. Baker’s analyzed G.P. acetone was 52 purified by the method of Shipsey and Werner^ except that, for the final drying before distillation, calcium sulfate ("Drierite*') was used in place of calcium chloride. iL* Isopropenyl acetate. Commercial isopropenyl acetate was distilled. The clear middle fraction (b.p. 97-98°) was used in the rate work. * A summary table of all the rate runs, and the re lated tables of data are given on p. 44 and on p. 71 ff. 52 _c. p-Toluenesulfonic acid. The Eastman Kodak pure-grade product was dried by codistilling the water with benzene* crystallizing the anhydrous material from benzene., and storing in a vacuum desiccator over phosphorus pentoxiqe before use. d. All other reagents used were prepared as described in Chapter II. 2. Completeness of Reaction of I C and Acetone. A solution containing 1.601 g. (0.00681 moles) of I and 10 ml. acetone in about 70 ml. ethylene chloride was pre pared in a glass stoppered flask and kept at room tempera ture for eight days. At this time* a negative test for sulfenyl halide was obtained* that is* no iodine was re leased when a small portion of the solution was shaken witlji aqueous potassium iodide solution containing starch indi cator. The solvent and excess acetone were evaporated at room temperature on the aspirator* leaving a yellow solid. About 15 ml. of absolute ethanol was added and the mixture heated to boiling. Cooling to 0° yielded 1.654 g. (0.00646 moles of aeetonyl sulfide); yellow crystals* m.p. 138-9°. Yield: 95.0 per cent. After drying at 85° for three hours* the weight of product was 1.648 g. (94.4 per cent yield) and the melting point fell to 135-6°. 53 3. Independent Synthesis of 2,4-Pinitropheny1 Aeetonyl Sulfide. To a solution of 2,4-dinitrothiophenol (1.5 g. m.p. 129-30°) in 50 ml. ethanol, 5 ml. of 28 per cent potassium hydroxide (in ethanol) and about 1 ml. of bromoacetone were added.^ The mixture was warmed on the steam bath for five minutes and then poured into about 300 ml. of ice water. A gummy, brown solid was separated and recrystallized (with prior decolonization) from ethanol, yielding fine yellow crystals, m.p. 139-41°. There was no depression in melting point on admixture with the aeetonyl 2,4-dinitrophenyl sulfide prepared via I plus acetone. 4. Independent Synthesis of 2,4-Dinitrophenyl Phenacyl Sulfide♦ 2,4-Dinitrothiophenol and phenacyl bromide were allowed to react at room temperature in ethylene chloride for.about two hours. The solvent was removed on the aspirator and the resultant solid re- crystallized twice from ethanol, giving yellow crystals, m.p. 168-70°. A mixture with 2,4-dinitrophenyl phenacyl sulfide (m.p..168-70°), prepared from I and acetophenone, melted at 168.5-169.5°• 5. Preparation of the 2,4-Pinitrophenylhydrazone of 2,4-Dinitrophenyl Aeetonyl Sulfide. To a solution of 0.4 g. of aeetonyl sulfide in 20 ml. hot ethanol was______ 54 added, in one portion, 10 ml. 2,4-dinitrophenylhydrazine 53 solution. Immediate precipitation of a voluminous orange solid was observed. The mixture was kept at room tempera ture for ninety minutes, and the solid product was sepa rated, washed with warm ethanol and recrystallized from an ethanol-chloroform mixture. The yellow-orange product melted (with decomposition) at 202-203.5°. A mixture of this substance with 2,4-dinitrophenylhydrazine (m.p. 195-6°) melted at 175-77°. The product was recrystallized from chloroform, and bright orange crystals which softened at 203-5°, and finally melted with decomposition at 210-11°, were obtained. Further recrystallization from chloroform did not change the crystalline form or melting behavior. Anal. Calculated for C-^H^NgOg: C,41.28; H, 2.77; N, 19-26. Found: C, 41.49, H, 2.86; N, 19X14. 6. Preliminary Rate Studies Using Small Excess of Acetone. a. A solution of 4.369 g. acetone in 200 ml. of ethylene chloride was prepared, and 25 ml. of it was added to a solution of 1.0991 g. of I in 75 ml. ethylene chlo ride in a glass stoppered, 125 ml. flask. Both solutions were kept in the constant temperature bath at 26.5° for several hours before mixing. At irregular intervals, 10 ml. aliquots of the solution were titrated as described 55 in Chapter II. No significant decrease in titer during the first day was observed* and, after four and one-half days, the titer had dropped only 8 per cent. b. A solution of 1.3004 g. of I in 100 ml. acetic acid was prepared and brought to 26.5° in the constant temperature bath. Acetone (2 ml.) was added, and the solu tion mixed and replaced in the bath. Aliquots were titrated as described in (6) above. No significant drop in titer was observed the first day, and in five days the titer had dropped only 13 per cent. 7* Preliminary Rate Studies Using Large Excess of Acetone. These runs were all carried out as follows: The desired amount of I was dissolved in 100 ml. of the solvent (measured by pipette) in a glass stoppered flask and then placed in the constant temperature bath at 26.5°. After an hour or so 25.0 ml. of acetone (kept in the same constant temperature bath) were added by pipette and the mixture was shaken vigorously. . Aliquots (10.0 ml.) were removed at approximately one hour intervals and titrated for sulfenyl halide content. The amount of I used in various runs varied from 1.5 to 3*0 g. The solvents em ployed were ethylene chloride and acetic acid; and these two solvents with added anhydrous hydrogen chloride. Plots of molar concentration of I vs. time were 56" prepared and compared with each other. Kinetic plots, for a first-order dependence in I were also prepared and the corresponding rate constants calculated. Regular* Rate Studies Carried Out in Transparent Flasks. a. Runs 1 through 6 were carried out as follows: The desired amount of I was weighed accurately, directly into a 300 cc. glass stoppered flask and 200 ml. of the solvent was pipetted .in. The flask was swirled until all the sulfenyl halide dissolved and was then brought to 26'.5° (i 0*1°). After about an hour, 50.0 ml. of acetone, also at 26.5°j was added, and the mixture was shaken vigorously and replaced in the bath. Aliquots (10.0 ml.) were removed at irregular time intervals and titrated for sulfenyl halide content as previously described. All i o glassware was oven-dried at 120 C for at least two hours before use. b. Rim 5 was carried out exactly the same as those above, except that the solvent was prepared as fol lows: Approximately 300 ml. of ethylene chloride was saturated, at room temperature, with dry hydrogen chloride gas. The concentration of hydrogen cfrloride^was found (by titration with standard sodium hydroxide as previously described) to be 9.1338 N. Two hundred milliliters of 7 this solution (containing 0.027 mole of hydrogen chloride) Hi.5 # Run 3 (| Run k* Plotted -Log(ArSCl) +0.1 10 Time (hrs.) FIGURE 2. : 5 - 8 “ was used as solvent. jc. Run 6 was carried out as described in a above except that the solvent was prepared as follows: Approxi mately 250 ml. of acetic acid were weighed into a tared flask and dry hydrogen chloride gas passed in. The amount of hydrogen chloride absorbed (2.41 g.) was determined by weight difference, and the concentration calculated to be approximately 0.053 moles of hydrogen chloride in the 200 ml. of the solution used. 1 9* Effect of Volume Changes During Mixing of Solu tions and Adjusting of Temperature. Aliquot portions of the solvents in the desired proportions were pipetted directly into a glass stoppered graduated cylinder, mixed, and allowed to come to temperature equilibrium in the constant temperature bath at 26.5°. The acetone used had been previously brought to 26.5°, whereas the other solvent was measured at room temperature, which was 21°. After temperature equilibrium had been reached (several hours) the volume of the mixture was read. The results are recorded in Table XI*. y 10. Regular Rate Studies Carried Out in Black Flasks. a. Runs 7 through 12 were carried out exactly as described in (8-a) above except that the flasks and stoppers used were painted with a heavy black asphalt paint. ________ 59 TABLE XI EFFECT OF VOLUME CHANGES LURING MIXING OF SOLUTIONS ANL ALJUSTING OF TEMPERATURE Volume Acetone Taken ml. Solvent Taken Volume of Mixture at 26.5° ml. Volume* Ratio of Acetone Volume** i ml. 25 100.0 ml. ethylene chloride 125.75 50-‘ 250 251.5 50 75.0 ml. ethylene chloride 126.5 100 250 253.0 25 100.0 ml. acetic acid 124.35 50 250 248.7 10 90.0 ml. acetic acid 99.5 25 250 248.8 25 100.0 ml. carhon tet rachloride 126.5 50 250 253.0 Volume of acetone taken divided "by total volume taken. ** Actual volumes used in rate run utilizing this ratio of acetone.' _____ . b. Runs 14 and 13 were carried out simultaneously (side by side in the constant temperature bath) using identical conditions and reagents, by the procedure de scribed in (8-a) above. In Run 14, however, a transparent flask was used whereas Run 13 was performed in a black flask. c _ . Run 15 was carried out as described in a . , above, using carbon tetrachloride as solvent. d. Runs 18 and 16 were carried out as described in a, above, except that 150 ml. pf solvent and 100.0 ml. of acetone were used. e _ . Runs 19 and 17 were carried out as described in a, above, except that 225.0 ml. of solvent and 25.0 ml. of acetone were used. £\ Run 20 was carried out as described in a, above, using as solvent acetic acid in which 4.7 g. of lithium chloride (dried at 110° for 2 hours) was dissolved. j£. Run 21 was carried out as described in a, above, using ethylene chloride as solvent and with the flask about one-third filled with solid glass beads, each approximately three millimeters in diameter. Before use, the beads were carefully washed with hot ethylene chloride and acetone and oven dried at 110°. h. Run 22 was carried out as described in a, above, using, as solvent, acetic acid in which 2.461 g. Curve I Run 15 Run 10 Curve II Curve III: Run 4" *Plotted Log(ArSCI) + 2 C O 0.6 III 0.2 125 100 Time (Mrs.) FIGURE 3 (ArSCl) 0.7 C V J + 0.5 f a O 3 0.3 Run 14 Run 13 Plotted Log (ArSCl) +2.1 0.1 10 20 Time (hrs.) RIGORE-ik Curve I Curve II Curve III Run 21 Run 23 Run 10' Plotted Log(ArSCl) +2.5 on I —I o i p r p . ± . C . 1.0 0.8 II' 0.6 h i 0.2 100 125 Time (Hrs.) FIGURE 5 . 2.0 Mole.Fraet. Acetone Curve 0.212 0.417 0.154 co 0.107 0.00592 +1.2 Plotted Log(ArSCl) + 2 £0.8 0.6 0.2 200 250 150 100 Time (hrs.) FIGURE 6 55 of p-toluenesulfonie acid was dissolved. i _ . Run 23 was carried out as described in a, above, except that after the acetone had been added, 2 ml. of distilled water was added and the flask was shaken vigorously. After the last point had been taken the solution was filtered, and a fine yellow solid collected. This was washed with acetone several times (even though the filtrate was not colored after the first wash), sus pended in refluxing acetone, thdn separated and dried in a pistol at 100°. The product decomposed at 285-300° (Fisher-Johns block), but its decomposition behavior was not exactly like that of bis-(2,4-dinitrophenyl) disulfide. It was probably a. mixture of the disulfide with other 82 products of the hydrolysis of the sulfenyl chloride. 11• Attempted Aluminum Chloride Catalysis of the Re action of I with Acetone. A solution of 3*0 g. (0.0128 mole) of I in 300 ml. ethylene chloride was placed in a 500 ml. flask fitted with a stirrer and cooled to *-3°• Acetone, 2.0 ml. (approx. .0.025 moles), and 13 g. of aluminum chloride (0.097 moles) were added and the solu tion stirred for four hours keeping the temperature at -3° (ice-salt bath). No red color, characteristic of the complex of AlCl^ with I, was observed. After this time 110 ml. 6 N HC1 solution was added with stirring, keeping .. 6K the temperature below 10°. The organic layer was separatee., dried over sodium sulfate, and excess cyclohexene added. After several hours at room temperature the solvent was removed (aspirator) and about 5 ml. of absolute ethanol added, giving 3.65 g. of yellow crystals, m.p. 118-9°, corresponding to 0.0115 moles 2-chlorocyclohexyl 2,4- dinitrophenyl sulfide. 12* Attempted Pyridihe Catalysis of the Reaction of I with Acetone. To a solution of 4.01 g. (0.0170 moles) of I in 100 ml. ethylene chloride were added 10 ml. of acetone and 10 drops of pyridine. After about 10 minutes a yellow precipitate was observed, which gradually in creased in amount during the next twenty-one hours. The solution, which still gave a positive test for sulfenyl halide, was heated to boiling on the steam bath but the precipitate did not dissolve. After two hours refluxing I the solution gave a negative test with potassium iodide- starch reagent. The insoluble material was separated, and washed with ethylene chloride. It proved to be O.83 g, of a material corresponding in melting point behavior (darkening but not melting 220-300°) to bis-(2,4-dinitro- phenyl) disulfide. t The filtrate from the above (combined with the ethylene chloride washings) was evaporated to dryness and 6 _ _ the resulting yellow solid recrystallized twice (with charcoal decolorization) from absolute ethanol, yielding 1.14 g. yellow crystals, m.p. 137-138.50. 13. Reaction of I with Pyridine. A solution of 5-0 g. (0.021 moles) I and 2.0 ml. pyridine (dried over cal cium hydride) in 200 ml. ethylene chloride was prepared in a glass stoppered flask and set aside in a dark cabinet for two days. The yellow crystalline precipitate (O.65 g. ) was separated, and it was noted that in the filtrate, almost Immediately, a yellow precipitate began to form — even though the volume of the solution was being increased by added solvent used to wash the original precipitate. The filtrate was therefore allowed to stand 24 hours more, after which time filtration yielded 1.22 g. of yellow solid. Again a precipitate appeared almost im mediately in the filtrate, so the procedure was repeated, yielding 1.30 g. more yellow solid. All three of the above solids behaved similarly to bis-(2,4-dinitrophenyl) disulfide (darken and decompose 230-300°) on the melting block. The final clear filtrate was concentrated to a volume of about 10 ml. on the aspirator, yielding 1.68 g. of pale yellow solid. When a sample was removed for melting point determination, it liquefied before it could . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i : 58’ be placed on the melting point block. Recrystallization from ethylene chloride gave extremely hygroscopic white crystalline material, which, when dissolved in water, gave a solution with a pH of about 4 (universal indicator paper), a strongly positive test with silver nitr&te, arid a negative test with potassium iodide and starch. The substance was undoubtedly pyridine hydrochloride. 14. Attempted Catalysis of the Reaction of I _ and Acetone with Ultraviolet Light. A solution of 5.0 g. (0.021 moles) I and'2.0 ml. (approx. 0.028 moles*) acetone in 100 ml. ethylene chloride was placed in a water-cooled ultraviolet light cell and illuminated with ultraviolet light for six hours. The solution (which still gave a strongly positive iodide-starch test) was filtered, giving 9*.5vl £.«. .(fiv,QQ&£5.jnoles?) of a brown solid corresponding in melting point behavior to bis-(2,4-dinitrophenyl) disulfide; see above. Cyclohexene (3*9 ml.) was added to the filtrated and, after standing forty-eight hours, it gave a negative stareh-iodide test. Removal of the solvent at the aspirator yielded a dark oil, which, on addition of a small amount of absolute ethanol, was converted to a yellow amorphous solid. . This was recrystallized from absolute ethanol (with chrircoal decolonization) yielding 2.78 g. (0.0088 moles) of 2-ehlorocyclohexyl 2',4l -dinitrophenyl sulfide, m.p. 59 117-18°; mixed melting point with authentic material 116.5-118°. 15. Reaction of Isopropenyl Acetate and 1. A solu tion of 2.5 g. (0.0106 moles) of I and 25.0 ml. isopropenyl acetate, in 50.0 ml. ethylene chloride, was prepared and set aside at room temperature for three weeks. A negative stareh-iodide test was obtained at this time. Evaporation of the solvent (aspirator) led to a red tar. Addition of chloroform to the latter produced a tan amorphous powder, m.p. 130-32°, which, when recrystallized from a mixture of ethyl acetate and Skellysolve B, gave yellow-orange crystals m.p. 135-36°, mixed melting point with authentic 2,4-dinitrophenyl aeetonyl sulfide (m.p. 139-40°) was 135.5-38°. Several repetitions, with minor variations, of this procedure gave similar results. Rate Studies Using Isopropenyl Acetate. Runs 24 and 25 were carried out as described in (10-a), above, using ethylene chloride as solvent, and isopropenyl acetate in place of acetone. ■ * - 7 * Isolation of Product from Rate Runs. In nans 8, 14, 17, and 19, after the last point had been taken, the remaining solution was left undisturbed at room tempera 70 ture until a negative test for sulfenyl halide was ob tained. , The solvent was then evaporated (steam bath and .aspirator) and the resulting yellow solid recrystallized from ethanol. In each case the product thus obtained cor responded in melting point and solubility behavior to 2,4-dinitrophenyl acetonyl sulfide, and did not depress the melting point of authentic acetonyl sulfide. Temp.: 26.5° TABLE XII Run 1 Solvent: CH2C1CH2C1 Time (hr.) Gone. ArSCl xl02 (m/l) Log. ArSCl Cone.. x(-l) k (first order) 1. 0 6.532 1.18495 2* 2 6.063 1.21733 .0373 3. 4 5.853 1.23263 .0275 4. 6 5.471 1.26192 .0295 5. 7.17 5.380 1.26921 .0271 6. 9 5.033 1.29817 * .0290 7. 10 4.914 1.30859 .0285 8. 11.25 4.725 1.32562 .0288 9. 12.5 4.583 1.33886 .0284 H O • 23 3.520 1.45346 .0269 H H • 24 3.473 1.45933 .0263 • CM H 25.25 3.475 1.45908 .0250 13. 28.5 3.041 1.51699 .0268 14. 30 2.929 1.53330 .0267 15. 31.67 2.830 1.54823 .0264 16. 34 2.744 1.56163 .0255 17. 36 2.464 1.61836 .0277 H 00 • 49.5 1.874 1.72724 .0253 Average rate constant .0277 72 Temp.: 26.5° TABLE XIII Run 2 Solvent: ch5cooh ......... Time . . (hr.) , . , Cone. ArSCl ....xlO2 (m/1) .. Log. ArSCl Cone. x(-l) k (first order) . 1 . 0 6.538 1.18454 2. 2 6.094 1.21512 .0412* ; 3. 4 5.866 1.23168 .0271 4. 5 5.582 1.25322 .0316 5. 6 5.472 1.26188 .0297 6. 7 5.430 1.26521 .0265 7. 9 4.983 1.30264 .0302 ' 8. 10 4.784 1.30736 .0283 ; 9. 11.25 4.762 1.32225 .0282 ■10. 12.5 4.416 1.35000 .0314 11. 23 3.530 1.45229 .0268 12. 26.5 3.311 1.48007 .0257 13. 28.5 3.165 1.49966 .0255 • H 31.5 2.801 1.55277 .0269 15* 34 2.646 1.57745 .0266 16. 36 2.489 1.60399 .0268 1.7.' 49.33 1.841 1.73501 .0257 ' Average rate constant .0278 Omitted in calculating average rate constant. 73 TABLE XIV Temp.r '26.5° Run 3 Solvent: CHgClCHgCl Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. x(-l) k (first order) 1. 0 8.763 1.05737 2. 2 8.275 1.08223 .0286 3. 4 7.692 1.08995 .0326 4. 5 7.712 1.11283 .0255 5. 6 7.323 1.35309 .0299 6. 7 7.128 1.14703 .0295 7. 9 6.712 1.17315 .0296 8. 10.5 6.471 1.18903 .0289 9. 11.75 6.257 1.20363 .0287 10. 22.5 4.863 1.'315 54 .0264 11. 24 4.620' 1.33538 .0267 12. 26.25 4.409 1.35566. .0262 13. 28.5 4.'105 1/38670 .0266 14. 31 3.860 1.41341 .0265 15. 33 3.520 1/45346 .0276 16. 34.5 3.491 1.45705 .0267 17. 36 3.542 1.45075 .0252 18. 48.75 2.629 1.58021 .0247 Average rate constant .0276 Temp.: 26.5° TABLE XV Run 4 Solvent: CHjCQOH 1 Time (hr.) Cone. • ArSCl xl02 (m/1) Log. ArSCl Cone * x(-l) k (first . order) . 1. 0 8.810 1.05502 2. 2 8.256 1.08325 . .0325 3. 4' 7.834 1.10604 .0294 4. 5 7..'541 1.12230 .0310 5. 6 7.301 1.13664 .0313 6. 7 7.094 1.14914 .0310 7. 9 6.690 1.17461 ^0306 8. 10.5 6.495 1.18745 .0291 9. 11.75 6.254 1.20387 .0292 10. 22.5 4.793 1.31944 .0271 11.' 24 4.694 1.32850 .0262 12. 26.25 4.323 1.36412 .0271 13. 28.5 4.187 1.37808 .0261 14. 29.75 3.952 1.40320 .0270 15. 31 3.836 1.41616 .0268 16. 33 3.655 1.43715 .0267 17. 36 3.456 1.46149 .0260 18. 48.75 2.596 1.58572 .0251 Average rate constant *0282 Temp.: 26.5° TABLE XVI Run 5 Solvent s CHpClCHpCl +HC1 . Time (hr. ) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. . x(-l).... k (first order) 1. 0 6.561 1.18306 2. 2 6.157 1.21063 .0318 | 3. 5 5.562 1.25478 .0330 4. 7.25 5.098 1.29261 .0336 5. 10 4.937 1.30654 .0284 6. 11.25 4.660 1.33161 .0304 7. 12.5 4.402 1.35635 .0319 8. 23.5 3.477 1.45885 .0270 9. 24.5 3.493 1.45680 .0257 , 10. 25.5 3.405 1.46791 .0257 ' 11. 27 3.120 1.50585 .0275 12. 29.5 2.891 1.'5389 5 .0279 13. 30.5 2.798 1.55315 .0279 14. ■31.5 2.721 1.56530 .0280 15. 34 2.599 1.58521 .0272 : 16. 35.5 2.489 1.60398 .0273 17. 36.5 2.478 1.60591 .0267 ; 18. 50.25 lV.68.2 1.77418 .0271 Average rate constant .0290 ; 76 Temp.s 26.5° TABLE XVII Run 6 Solvent: CBUCOOH P+HC1. Time (hr.) Cone. ArSCl xlO2 (m/l) Log. ArSCl ■ Cone. x(-l) k (first order) 1. 0 6.609 1.17988 2. 1 6.460 1.18980 .0229* 3. 5 5.369 1.27013 .0416* 4. 7.5 5.300 .1.27576 .0294 5. 10 4.868 1.31267 .0306 6. 11.25 4.621 1.33528 .0318 7. 12.5 4.411 1.35551 .0324 8. 23.5 3.483 1.45806 .0273 9. 24.5 3.406 1.46780 .0271 10. 25.5 3.383 1.47074 .0263 11. 27 3*265 1.48619 .0261 > • CM H 28.5 3.145 1.50242 .0261 13. 30.5 2.971 1.52715 .0262 14. 31.5 2.832 1.54782 .0269 15. 34 2.571 1.58999 .0278 16. 35.5 2.427 1.61503 .0282 2.7. 50.25. 1.625 1.79920 .0284 Average rate constant .0283 * Omitted in calculating average rate constant. 77 TABLE XVIII Temp,: 26.5° Run 7 Solvent: CHgClCHg-Cl Time (hr.) Cone. ArSCl xLO*- (m/l) Log. ArSCl Cone. x(-l) k (first order);. 1. 0 7.282 1.13775 2. 1 6.971 1.15670 .0436 3. 2.5 6.954 1.15777 .0184 4. 4.08 6.553 1.18356 .0258 5. 5.5 6.472 1.18896 .0214 6. 8.25 5.551 1.25563 .0329 7. 10 5.285 1.27696 .0308 8. 11.25 4.999 1.30112 .0334 9. 22.83 3.691 1.43286 .0298 10. 24.5 3.849 1.41465 .0260 11. 26 3.398 1*46878 .0293 12. 27.75 3.309 1.48030 .0284 13. 29.5 3.019 1.52014 .0299 14. 32 2.746 1.56130 .0305 15. 33.5 2.594 1.58603 .0308 16. 35 2.553 1.59295 .0300 17. 48 . . 1.721 1.76422 .0301 Average rate constant .0294 Temp.: 26.5° .TABLE XIX Run 8 Solvent: ch2cich2ci . Time (hr.) Cone. ArSCl xl02 (m/1) Log. ArSCl Cone.’ x(-l) (first order); 1. 0 6.064 1.21724 2. 1.5 5.805 1.23620 .0291 3. 2.5 5.634 1.24918 .0294. 4. 3.75 5.382 1.-26906 .0318 5. 8.75 4.568 1.34030 .0324 6. 21.08 3.301 1.48135 .0290 7. 24.33 3.253 1.'48772 .0256 8.' 27.58 2.907 1.53655 .0267 9. 30.25 2.472 1.60695 .0297 10. 31.75 2.403 1.61925 .0296 11. 32.75 2.384 1.62275 .0290 12. 45.5 1.853 1.73212 .0261 13. 47.67 ■ 1.953 1.75780 .0260 14. 51.67 1.413 1.84996 .0282 15. 56.85 1.080 1.96662 .0304 Average rate constant .0288 Temp.: 26.5° TABLE XX Run 9* Solvent: ch2cich2ci Time (hr.,,). Cone. ArSCl xlO^ (m/1) Log. ArSCl Cone. +3 k (first order) 1. 0 8.376 1.‘ 92302 2. 1 8.157 1.9U55 .0264 3. 4.5 7.223 1.90477 .0329 4. 5.62 7.194 1.'85697 .0271 5* 7 5.955 1.84227 .0266 6. 10.5 6.297 1.79916 .0272 7. 12.5 5.932 1.77320 .0276 8. 22.5 4.606 1.66328 .0266 9. 25.5 4.206 1.62382 .0270 10. 28.5 3.878 1.58873 .0270 11. 36 3.030 1.48140 .0283 . CM H 45.5 2.532 1.40346 .0263 13. 49 2.361 1.37310 .0259 14. 56 1.957 1.29149 .0260 Average rate constant .0273 * Temperature control was poor during this run. 80 TABLE XXI Temp.: 26.5° B m 10 Solvent: CH2C1CH2C1 Time (hr.) Cone. ArSCl xlO^ (m/l) Log. ArSCl Cone. +3 k (first order) 1. 0 7.926 1.89905 2. 2 7.449 1.87212 .0310 3. 5.451 1.73650 .0288 4. 15 5.155 1.71223 .0287 5. 18.5 4.647 1.66712 .0289 6. 23.5 3.940 1.59554 .0297 7. 25.5 3.714 1.56980 .0297 8. 38 2.668 1.42625 .0287 9. 40.5 2.463 1.39140 .0289 10. 43 2.307 1.36305 .0287 11. 63.5 1.’ 293 1.11160 .0286 12. 67.5 1.099 1.04100 .0293 13. 84.5 0.679 0.83168 .0291 14. 90 0.491 0.69117 .0309 . Average rate constant .0295 81 TABLE XXII Temp.: 26.5° Run 11 Solvent! CH2C1CH2C1 Time . . . (hr.) Cone. ArSCl xlO2 (m/1) log. ArSCl Cone . +1 k (first ^ order)' 1. 0 7.652 .88375 2. 1 7.572 .87920 .0274 3. 3 7.168 .85537 .027? 4. 4 7.014 .84597 .0255 5. 8 6.323 .80090 .0258 6. 10 5.922 .77245 .0273 7. 12 5.638 .75111 .0268 8. 14 5.262 .72118 .0280 9. 23 4.110 .61388 .0278 10. 24 4*084 .61104 .0269 11. 28 3.559 .55132 .0280 12. 30 3.514 .54574 .0265 13. 34 2.905 .46313 .0290 14. 36 2.753 .43979 .0289 15. 48 1.999 .30088: .0283 16. 49 2.159 .33315 .0262 17. 54 1.888 .27596 .0262 18. 58 1.468 .16663 .0288 Average rate constant .0273 82 TABLE XXIII Temp.: 26.5° Run 12 Solvent: CH^COOH Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +1 k (first order) ; . 1. 0 8.4756 .92817 2. 1 8.2024 .91394 .0328 3. 3 7.9219 .89883 .0225 4. 4 7.6855 .88567 .0245 5. 6 7.3144 .86503 .0239 6. 8 6.8517 .83580 .0266 7. 10 6.3967 .80596: .0282 8. 14 5.7404 .75894 .0278 9. 23 4.5990 .66266 .0266 10. 24 4.4323 .64663 .0270 11,. 28 4.0699 .60958 .0262 ' 12. 30 3.8695 .58766 .0261 13. 34 3.4888 .54268 .0261 14. 36 3.1344 .49615 .0276 15. 49 2.3250 .36642 .0264 16. 52 2.2141 .34520 .0258 17. 54 2.1576 .33397 .0253 : 18. 58 1.8878 .27596 .025,9 1 Average rate constant .0265 83 TABLE XXIV Temp.: 26.5° Run 13 Solvent: CE^ClCHgCl Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +1 k* (first order) 1. 0 6.7031 .83628 2. 1 6.7212 .82745 3. 3 6.2047 .79272 .0258 4. 5 5.6053 .74860 .0358 5. 8 5.3525 .72856 .0281 6. 9 5.1470 .71162 .0293 7. 10.5 4.8902 .68933 .0300 8. 23 3.6485 .56211 .0265 9, 24 3.5199 .54653 .0268 10. 27 3.3638 .52683 .0290 11.' 29.5 3.0310 .48159 .0269 12. 33.5 2.5777 .41123 .0285 13. 34.5 2.3448 .37011 .0205 M - 46.5 1.8242 .26107 .0280 15. 47.5 1.8062 .25677 .0276 16. 51 1V5171 .18101 .0291 17. 52 1.5214 .18224 .02&5 , Average rate constant .0287 * Rate constants calculated from point 2. 84 TABLE XXV Temp.: 26.5° Eun 14 Solvent: CH2C1CH2C1 Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +1 k (first order) 1. 0 6.6647 .82378 2. 1 6.3752 .80449 .0444* 3. 3 6.1050 .78569 .0292 4. 5 5.9458 .77421 .0228 5. 6 5.6577 .75264 .0273 6. 8 5.1209 .70935 .0329 7. 9 4.8903 .68934 .0344 8. 10.5 4.7291 .67478 .0327 9. 23 3.5088 .54516 .0279 10. 25 3.1696 .50101 .0297 11. 27 3.2141 .50706 .0270 12. 29.5 2.9994 .47703 .0271 13. 33.5 2.4677 .39229 .0297 14. 46.5 1.7668 .24719 .0286 15. 47.5 1.5621 .19371 .0306 16. 51 1.5527 .19109 .0286 17. 52 1.5270 .18384 .0283 Average rate constant .0293 * Omitted in calculation of average rate constant. Temp.: 26.5° TABLE XXVI Run 15 Solvent: CCl^ Time (hr.) Cone. ArSCl xlO2 (m/l)) Log. ArSCl Cone. +3 k (first order) 1. 0 6.285 1.79827 2.' 3 5.912 1.77174 .0204 3. 11.5 5.105 1.70800 .0181 4. 25 4.185 1.62164 .0163 5. 29.33 3.066 1.'48657 .0245 6. 32.83 3.268 1.51432 .0199 7. 36.5 3.148 1.'4980 6 .0189 8. 48.5 2.402 1.38063 .0198 9. 52 2.209 1.34427 .0201 10. 58 2.076 1.31727 .0191 11. 72 1.545 1.18904 .0195 12. 75.5 1.472 1.16776 .0192 13. 78.5 1.341 1.12746 .0197 14. 97.5 0.951 0.97800 .0194 13. 100 0.979 0.99096 .0186 16. 102 0.940 0.97290 .0186 17. 122.17 0.569 0.75496 .0197 Average rate constant .0195 86 TAB1E XXVII Temp.: 26.5° Him 16 Solvent: CH2C1CH2C1 Time .(hr.*) Cone. ArSCl xlO^ (m/1) Log. ArSCl Cone. +3 k (first order) 1. 0 5.417 1.73375 2. 2 3.944 1.59596 .1587 3. 3 3.524 1.52704 .1587 4. 4 3.011 1.47865 .1469 5. 5 2.529 1.40291 .1524 6. 7.33 1.834 1.26331 .1477 7. 8.67 1.611 1.20710 .1400 8. 12.17 1.310 1.11737 .1167* 9. 22 0.0 Average rate constant .1507 * Omitted in calculating average rat e c ons t ant. 87 TABLE XXVIII Temp,s 26*5° Run 17 Solvent: CH2C1CH2C1 Time ....(hr..).... Cone. ArSCl xl02 (m/1) Log. ArSCl Cone. +3 k (first order) 1. 0 11.838 2.07228 2. 1.’ 25 11.610 2.06483 .00137* 3. 14.25 10.659 2.02770 .00720* 4. 19.25 10.432 2.01837 .00645 5. 39.25 9.253 1.96628 .00622 6.' 44.25 8.987 1.95361 .00618 7. 64.75 7.814 1.89287 ' .00638 8. 68.75 7.732 1.88829 .00616 9. 85.75 6.978 1.84373 .00614 10. 108.33 6.222 1.79393 .00592 11. 115.75 5.965 1.77561 .00590 12. 143 5.016 1.70036 .00599 13. 159.25 4.653 1.66773 .00585 14. 186.25 4.006 1.60271 .00581 15. 207.25 3.590 1.55509 .00575 16.‘ 259.25 2.617 1.41780 .00581 17. 282 2.281 1.35813 .00583. Average rate constant .00605 * , Omitted in calc-ulating average rate constant. 88 TABLE XXIX Temp.: 26.5° Run. 18 Solvent: CH^COOH Time (hr.) Cone. ArSCl x1Q2 (m/1) Log. ArSCl Cone. +1 k i (first order) 1. 0 5.8160 .76462 i 2. 1 5.0626 .70437 .1388 3. 2 4.4442 ..64779 .1345 4. 3 4.0173 .60393 .1234 ■ 5. 4.5 3.2690 .51442 .1281 6. 6 2.5900 .41330 .1344 7. 7 2.3419 .36957 .1300 8. 9 1.7690 .24773 .1323 9. 10 1.5246 .18316 .1339 10. 11 1.3266 .12274 .1344 Average rate constant .1322 89 TABLE XXX Temp.: 26.5° Run 19 Solvent: CH^COOH Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone.’ +3 k (first order) 1. 0 8.239 1.91588 2. 2 8.062 ' 1.90646 .01089* 1 3. 8,5 7.937 1.89967 .00439* 1 4. 23 7.089 1.85060 .00654 5. 26.5 6.947 1.84177 .00644 6. 45.: 5 5.855 1.76745 .00751 7. 49 5.747 1.75946 .00735 8.: 56.5 5.478 1.73868 .00722 9. 69 5.080 1.70590 .00701 10. 75 4.744 1.67615 .00736 11. 94 4.219 1.62517 .00712 12. 99 4.416 1.61762 .00694 13. 118.5 3.543 1.54937 .00712 ; ■ 14. 142.‘ 5 3.066 1.48656 .00694 ' 15. 167.83 2.387 1.37787 .00738 16. 190 2.015 1.30434 .00741 17. 213.5 1.678 1.22482 .00745 . Average rate constant .00715 * Omitted in calculating average rate constant. 90 Temp*: 26.5° TABLE XXXI Run 20 Solvent: CH^COOH Time (hr.) Cone. ArSCl xlO2 (m/l) Log. ArSCl Cone* + 2 k (first order) 1. 0 6.6400 1.82207 2. 1 6.3197 1.80070 .0495 ; 3. 3 5.8237 1.76520 .0437 4. 5 5.1138 1.70874 .0522 5. 8 4.2906 1.63252 .0546 6. 9 4.0041 1.60649 .0552. 7. 10.5 3.8364 1.58392 .0523 8. 23 2.1132 1.32494 .0498 9.' 24 1.9803 1.29673 .0504 10* 27 1V8771 1.27349 .0468 11. 29.5 1.7362 1.23960 .0455 12. 33.‘ 5 1.1759 1.07037 .0517 13* 34.5 1.0862 1.03591 .0525 14. 46.5 .6198 .79225 .0510 15. 47.5 .5791 .76275 .0514 16. 51 .3939 .59539 .0554 17.‘ 52 .3665 .56407 .0557 Average rate constant .0511 91 TABLE XXXII Temp.: 26.5° Run 21 Solvent: CHgClGHgCl Time (hr..). Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone*' +3 k (first order) 1. 0 8.348 1.92158 2. 3 7.682 1.88545 .0277 3. 9 6.301 1.79944 .0313 4. 11.5 5.934 1.77338 .0297 5. 25 4.136 1 ,: 616 58 .0281 6. 29.17 3.560 1.55142 .0292 7* 30.58 3.353 1.52541 .0298 8. 32.17 3.227 1.50885 .0296 9. 36.17 2.881 1.45956 .0294 H O • 48.5 1.966 1.29363 .0298 11. 50.5 1.930 1.28558 .0290 12. 52 1.794 1.25380 .0296 13. 58.83 1.508 1.17849 .0291 14. 72 1.952 0.97841 .0270* 15. 73.5 0.821 0.91408 .0318* 16. 77.5 0.765 0.88366 .0310 . 17. . 97.5 . 0.270 0.43169 .0352* Average rate constant .0295 * Omitted in calculating average rate constant. 92 t Temp.: 26.5° TABLE XXXIII Run 22 Solvent: ch5cooh Time (hr.) Cone. ArSCl xl02 (m/l) Log. ArSCl Cone. +1 k* (first order) 1. 0 8.0749 .90714 2. 1 7.9603 .90093 I 3. 3 7.7338 .88839 .0144** : 4. 4 7.3879 .86852 .0249 5. 6 7.0693 .84938 .0238 6. 10 6.1933 .79192 .0279 7. 12 5.7717 .76130 '.0292 8. 14 5.5410 .74359 .0279 9. 24 4.3821 .64168 .0260 o H 28 3.9209 .59339 .0262 1 11. 30 3.9169 .59294 .0245 12. 36 3.0435 .48337 .0275 13. 48 2.2792 .35778 .0266 14. 52 2.1021 .32265 .0261 15. 54 2.0284 .30715 .0256 16. . 58 1.6979 .22991 .0268 ' ! Average rate constant .0264 * Rate constant calculated from point 2. ,*-* Omitted in calculating average_rat_e constant. 93 TABLE XXXIY Temp.: 26.5° Run 23 Solvent: CEUC1CHAC1 ^+h2o^ Time . , .(hr...)..... Cone. ArSCl xl02 (m/D Log. ArSCl Cone. +3 1. 0 6.895 1.83856 2. 2.33 5.746 1.75939 3. 3.75 5.151 1.71187 4. 4.75 4.734 1.67523 5. 6 4.271 1.63051 6. 8 3.924 1.59371 7. 12.83 3.054 1.48488 8. 22.5 1.939 1.28753 9. 25 1.689 1.22766 H O • 29.25 1.445 1.15972 11. 32.08 1.306 1.11584 12.' 50 0.846 1.92727 13. 56 0.949 0.97740 14. 57.25 0.714 0.85346 15. 71.83 0.485 0.68547 16. 7.5.5. 0.440 0.6429.6 Temp.: 26.5° TABLE XXXV Run 24 Solvent: ch2cich2ci Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +3 k (first order) 1. 0 \ 8.072 1.90697 2* 1.25 7.998 1.90300 .00731* 3. 15 7/399 1.86916 .00581* 4. 16 7.387 1.86848 .00554 5. 25.5 7.130 1.85311 .00486 6. 40 6.320 l.; 80075 .00612* 7. 42.5 6.649 1.82272 .00457 8. 65.5 6.067 1.78295 .00436* 9. 85 5.431 1*73491 .00456 10. 92 5.303 1.72454 .00457 11. 113 4.757 1.67737 .00468 12.' 137.5 4.243 1.62766 .00468 13. 143.58 4.048 1.60725 .00481 14. 158.5 3.763 1.57548 .00480 15. 187 3.232 1.50945 .00490 16. 208.37 2.799 1.44696. .00509 17. 259 2.161 1.33456 .00509 Average rate constant .00490 Omitted in calculating average rate constant. 95 TABLE XXXVI Temp.; 26.5° Rim 25 Solvent: CHgClCHgCl Time (hr.) Cone. ArSCl xlO^ (m/l) Log. ArSCl Cone • +1 k (first order)- 1. 0 7.7253 .88791 2. 1 7.6227 .88211 .0134* 3. 9 7.1469 .85412 .00865* 4. 10 7.3050 .86362 .00560* 5. 23 7.0130 .84590 .00421 6. 51.5 6.1962 .79213 .00428 7. 52 6.2164 .79354 .00418 8. 73.5 5.6301 .75052 .00431 9. 101 5.2000 .71600 .00392 10. 120.5 4.6961 .67174 .00413 11. 144.5 4.5735 .66025 .00363 12. 153.5 4.4191 .64534 .00364 13. 168.5 4.0708 .60968 .00380 14. 174.5 3.8138 .58136 .00405 15. 195.5 3.6806 .56592 .00379 16. 218.5 3.2412 .51071 .00398 Average rate constant .004045 * Omitted in calculating average rate constant. CHAPTER IV THE REACTION OF 2 * 4-DINITROBENZENESULFENYL CHLORIDE WITH ACETONE IN METHYL ACETATE I. INTRODUCTION In continuing the study of the reaction of I with acetone it was necessary to find a solvent in v\rhich the reaction occurred rapidly enough* with equivalent amounts of the reagents* for convenient kinetic studies. The dis cussion and experimental work done in connection with this problem are given in Part III* Chapter VI. For reasons discussed there* methyl acetate was chosen as the solvent for further work* and the studies conducted in this solvent are described herein. II. DISCUSSION Preliminary studies showed that the reaction be tween I and acetone in methyl acetate-produced the same product* 2*4-dinitrophenyl acetonyl sulfide, as was found in the solvents used previously. The reaction to form this product was essentially complete -- 93*3 per cent isolated yield -- in methyl acetate. It was also shown that the sulfenyl chloride could be titrated satisfactorily in this solvent* even after being kept in methyl acetate 97 at fifty degrees for twelve hours. Preliminary rate studies were then undertaken, ks the temperature used was fifty degrees, and the boiling points of acetone and methyl acetate are 56.5° and 57.1° respectively, it was apparent'that precautions against evaporation loss would have to be taken -- particularly losses which might occur during the time samples were being removed for analysis. When a pseudo rate run con sisting of I in methyl acetate in a standard-taper glass stoppered flask was carried out at fifty degrees, it was found that the titer of sulfenyl chloride increased about 10 per cent in seven days (ten aliquots were removed for > titration during this time). It was believed that this increase in sulfenyl chloride concentration was caused by evaporation of methyl acetate from the open flask dur ing the time samples were being removed. For this reason, the first rate studies were car ried out in glass stoppered (standard taper) test tubes (capacity about fifteen milliliters) prepared for this purpose. The tubes were filled with the original solution of I and acetone in methyl acetate, stoppered carefully, and placed in the constant temperature bath. When it was desired to make a determination, one of the tubes was •opened, the sample removed, and the remainder of the solu- tion in the tube discarded. In this manner evaporation ; g g - losses due to continual opening of a flask were prevented. It was found, however, that these precautions were not sufficient. The data obtained were erratic, and often when two determinations were made at almost the same time they differed by much more than the experimental error of the titration. It therefore appeared that evaporation was occurring past the standard taper stopper. Runs were therefore made in which the stoppers were sealed on with wax, but little improvement in results was observed. It was noted that the wax became discolored, and in some cases developed visible pinholes, presumably caused by the dissolving action of the methyl acetate vapors. Nevertheless, some reasonably satisfactory rate curves were obtained by these procedures. It was found that the data plotted best for first order kinetics, but that the rate constants varied greatly from run to run (see Runs 26-30). To eliminate the problem of evaporation, sealed ampoules were used. Because of the difficulty inherent in sealing ampoules containing such highly volatile and inflammable materials, special ampoules with fragile bottoms were constructed. These could be sealed (contain ing an exactly measured volume of the solution) at Dry Ice temperature, kept at fifty degrees, and then, when a de- termination, was-des-ired, cooled again to Dry Ice__________ ----------------------------------------- 99 temperature and broken under the surface of. the titration mixture. ' In this way, the volume of the solution used could be known accurately without requiring the sealing or opening of ampoules containing solvent at high pressure. When runs utilizing these ampoules were made, satisfactory data were obtained. It was found that the reaction, as was indicated by the preliminary studies, was first order with respect to sulfenyl chloride and zero order with respect to acetone. However, the first order rates were found to be directly proportional to the initial concentration of acetone. Thus, doubling the initial acetone concentration (keeping the initial sulfenyl chloride concentration the same) produced almost exact doubling of the observed first order rate constant, while if the initial acetone concentration was the same in two runs, the observed rate constants were also the same, k summary of the first order runs done at fifty degrees, and a plot of first order rate constants as a function of initial acetone concentration.for these runs is given in Table XXXVII and Pig. 7. This dependence of observed rate constant upon the initial concentration of a .component which did not enter into the rate expression for a given run could well be caused by reaction with, or catalysis by a product, as is illustrated -- for example -- by the reaction_Qf__ac.e_t.a-ts___ 100 TABLE XXXVII 'SUMMARY OP RUHS CARRIED OUT AT 50° AMU WITH HO ADDED ACID Run ■ . no.. Init. ArSCl (m/1) Init. Acetone (m/l) xlO hr. k^xlO2 Init* Acetone 31- .140 • .137 7.35 5.37 32 .252 .251 14.72 5.86 33 .134 .269 14.90 5.54 34 .140 .070 3.55 5.07 35 .170 .170 8.80 5.19 36* .122 .123 6.66 5.41 Average k-^ x IQ2 Init. Acetone 5.41 * Solution used contained added acetonyl sulfide 2.0 3 rk 1 •*1-5 2 U X J3- rH l.o (D Preliminary Run 3^init. (“-A.) JSKHJRE-7------- 102 ion with ft-propriolactone, in the study by Bartlett and 4 > Small. Runs with product added were therefore made in the present work. The addition of acetonyl sulfide (see Run 36) apparently made no significant difference; the reaction was still first order (in I) and the observed rate constant agreed with the value which would have been predicted from the initial acetone concentration had no acetonyl sulfide been added. When an excess of anhydrous hydrogen chloride was added, however (see Runs 37* 38, and 39); a significant difference was noted. The rate of the reaction increased considerably, and the reaction now plotted best for second order kinetics instead of first order. The second order rate constant thus obtained was independent of the amount of excess -acid used, and also independent of the initial concentrations, of the reactants, To test whether this effect was limited to hydrogen chloride or whether it was a more general acid catalysis, runs with added p-toluenesulfonic acid were made -- after showing that p-toluenesulfonic acid did not react with I under the conditions used. These runs also plotted for second order kinetics, and the rate constants obtained were similar to those using hydrogen chloride. The second order rate constants thus obtained varied from 0.14 to 0.23; depending upon the concentrations of reactants and 103 ' appears to be some tendency for the rate constant to de crease as the acid concentration is increased, but this is neither pronounced nor invariable. A summary of the second order runs made at fifty degrees is given in Table XXXVIII. Although it had already been shown (see Chapter III) that Lewis acids such as aluminum chloride tend to complex with acetone in preference to I, an attempt to catalyze the reaction with the mild Lewis acid, mercuric chloride, was made — after it had been shown that mercuric chloride was quite soluble in methyl acetate and was nonreactive towards I. The reaction with mercuric chloride present at a concentration of 0.14 M started as intermediate order (between first and second) but soon became second order -- probably as a result of the fact that the reaction pro duces hydrogen chloride, which should increase the tendency towards second order. The second order rate constant for the latter part of the reaction, calculated from the slope of the second order curve, agreed very well with the cor responding constant for the reaction with added hydrogen / chloride. The fact that excess acid shifts the reaction from first to second order makes it appear very remarkable that the runs with no added acid plot so well for first order -- for the reaction is producing hydrogen chloride, which____ 104 TABLE XXXVIII SUMMARY OS STMS CARRIED OUT AT EXCESS ADDED ACID 50° WITH Init. Init. Init. 3 e2 Sun ArSOl Acetone Acid CL . N-O. .(m/1). (m/1). (m/1) (m/1)J hr. 37 .115 .120 ,65a .136 38 .137 .138 . 52a .144 39 .201 .203 .38a .146 40 .199 .198 ,.06b .144 41 .196 .197 .19b .143 42 .099 .197 .14b .190 43 .195 .098 .13b .229 44 .198 .099 .115b .207 45 .050 .099 .116b .148 46 .197 .197 .12b .208 ■ 47 • 191 .191 . 245b .164 48 .100 .100 • 12b .163 a = hydrogen chloride b = p-toluenesulf onic acid H-H 105 should cause a tendency to shift to second order. It seemed possible that the effect of the increasing hydrogen chloride concentration as the reaction proceeded was being compensated for somehow — perhaps by the decrease in acetone concentration. One possibility-is that the reaction is actually third order; obeying the equation below, but that the product of acetone and hydrogen chloride concentrations is relatively constant during the main part of the run, lead ing to pseudo first order kinetics. This rate expression was therefore integrated and attempts made to evaluate the third order rate constant using the data of Runs 32 and 36. It was found, however, that consistent sets of rate con stants could not be obtained — the constant varied by a factor of at least ten during each run; and, in the case of Run 36, the constant was negative during half of the run. It was therefore apparent that the third order expression did not apply. Equation 1. -d(ArSGl)/dt = k(ArSCl)(CH^COCHg )(HC1) Another possibility is that the reaction is analo gous to those studied by Bell and Tantram^ and Zucker and 68 Hammett, in which the rate of enolization of acetone and the rate of addition to the enol are of comparable magni tude, leading to complex kinetics. To check this possi- : 3.06 bility, the differential expression (2) was derived for the case of equal initial acetone and sulfenyl chloride concentrations and comparable rates for the two step reaction below, assuming a steady state for the enol con centration. The letters y and z are the composite rate constants, k^/kg, and k-^k^kg, respectively, for the re action scheme of mechanism I. Equation 2. -d(ArSCl)/dt (1 4- ya/b) = za2 k - . Mechanism I: CH-COCH- + HC1 CHo=C(0H)CH, + HC1 3 3 *rz £ 3 2 k3 CH2=C(OH)CH3 - 9 - ArSCl — ^ CI^COCHgSAr 4- HOL The ArSCl concentration is represented by a, and I d represents the hydrogen chloride concentration. Large scale plots of sulfenyl chloride concentration vs. time were made for Runs 32 and 36V and values of -d(Ai?SCl)/dt at different ArSCl concentrations were obtained, by measuring the tangent of these curves at different points with a tangentmeter. Values for y and z were then cal culated and found to be inconsistent, indicating that this rate expression did not apply. Also, the reshlts of the experiments on the bromination of acetone in methyl acetate, described below, show conclusively that the two steps postulated, above for the reaction cannot be of 107 comparable rate. A third possible kinetic expression which might account for the data is equation 3* This expression would account for the first order kinetics -- for as the acetone concentration drops, the hydrogen chloride concentration increases, mole for mole, making the sum of acetone and hydrogen chloride concentrations a constant during a given run. This would give pseudo-first order kinetics, with the observed first order rate constant directly propor tional to initial acetone concentration, exactly as is observed. It would not, however, account for the switch to second order observed when excess hydrogen chloride is added, since the expression predicts that first order kinetics will be found no matter how much hydrogen chloride is added. It is possible, however, that the change to second order kinetics, on addition of excess hydrogen chloride or other acid, is caused by a change in mechanism or a change in rate-determining step under acid conditions. One possible mechanism which would lead to the above rate expression is as indicated below. Equation 3. -d (ArSCl )/dt = k(ArSCl) [ (C^COCH^ )+(HCl) ] Mechanism II: ArSCl --- > ArS+Cl~ ArS+Cl" + CHjCOCHj --» ArSCH2COCH3 + HC1 — . ---------- - ro8 The first step would presumably be aided by any substance capable of pulling off a negative chlorine atom -- perhaps by hydrogen bonding. Ordinary acetone should be relatively incapable of hydrogen bonding, but, in its enol form, it has a hydroxyl group which should be able to hydrogen bond to a partially negative chlorine. Hydrogen chloride itself should be capable of the same type of action, and the rate of the first step should therefore be: Equation 4. -d(ArSCl)/dt = (ArSCl) [k(enol) 4- kg(HCl)] Since the keto and enol forms of acetone are in rapid equilibrium (see below for discussion of the evidence: for this) one can substitute for the enol concentration its equivalent from the equilibrium expression K = v gsnol/keto, and, assuming the amount of keto form to be approximately equal to the amount of acetone, obtain the expression: -d(ArSCl)/dt = (ArSCl)[k1(CH^ If k-£ and kg are approximately equal, the desired expres sion, equation 3, is obtained. Addition of hydrogen chloride should increase the rate, and, if step two is normally only slightly faster than step one, it may make the rate of step one greater than that of step two, mak ing the latter rate determining. One method of testing this mechanism would be to COCHo )4-kg (HC1) ]. .. rag add or remove hydrogen chloride to check if the first order rate constant changes as the kinetic equation re quires. Since the addition of hydrogen chloride was al ready attempted and led to a change in rate determining step, attempts to remove the hydrogen chloride as it formed were made. The difficulty in finding a base non reactive towards I was discussed in the preceding chapter. Despite the adverse results discussed there, an attempt to use pyridine in the presence of I was made. A known solu tion of pyridine and I in methyl acetate,was sealed in am poules under conditions as nearly anhydrous as could be obtained without resorting to dry-box techniques, and the ampoules were broken open and their contents titrated for sulfenyl halide content over a period of six days. It was found that the titer dropped about 30 per cent during the first hour (during which time a precipitate ap peared in each vial) and then tended to level off. This is good evidence for' the supposition, already discussed, that the supposed interaction of pyridine with I is actually a pyridine-catalyzed reaction of I with traces of water present. Because of the low molecular weight of water, only a very small amount of it would be required to destroy comparatively larger weights of I; for example, less than seven milligrams of water per ampoule could ------- — . — , — ----------- -— —--• nxr * have caused the amounts of reaction observed. In view of this, and the known difficulties in preparing’ 'and using 28 rigorously dry pyridine, no attempts to use pyridine or similar tertiary amines as a scavenger for hydrogen chloride were made. Another base considered for this purpose was 2,4- dinitrophenyl 4'-dimethylaminophenyl sulfide — a compound which is known to be very weakly basic, but which does 12 form a hydrochloride. Two runs in sealed ampoules were set up at fifty degrees: the first consisted of I, 2,4- dinitrophenyl 41-dimethylaminophenyl sulfide, and acetone in methyl acetate, and the second, a 'blank' which was identical to the first -- except that no acetone was added. It was found that, in both runs, the titer for sulfenyl halide dropped rapidly, indicating that the sulfenyl chloride was reacting rapidly with the amino sulfide, which, of course, shows that compound to be unsuitable as a base for removing hydrogen chloride in the I-acetone runs. In view of the failure to find a base capable of removing the hydrogen chloride from the reaction without disturbing the sulfenyl chloride, it was necessary to try * V The hydrolysis of I has been studied by N. Kharasch and W. King,32 and the precipitated product, ArSSAr would be expected. Ill again to test the mechanism by addition of hydrogen chlo ride. Runs were therefore made in which the amounts of hydrogen chloride added were small, and it was found that, if the hydrogen chloride concentration were sufficiently small, the reaction remained first order. A summary of the data of these runs is given in Table XXXIX. The ob served first order rate constants for these runs were not proportional to the sum of the concentrations of acetone and hydrogen chloride as required by equation 3. With the exception of the run in which both acetonyl sulfide and hydrogen chloride were added, the rates were only slightly greater than they would have been had no hydrogen chloride been added. This disproves equation 3 completely. How ever, the abnormally high rate of Run 53, in which both acetonyl sulfide and hydrogen chloride were added, indi cated that something had been overlooked in the derivation of equation 3* namely that species in the solution other than acetone enol and hydrogen chloride might be catalyzing * step one. * There is also the possibility that the acetonyl sulfide is increasing the rate by itself reacting with I (catalyzed by hydrogen chloride). Therefore a run was made in which I, acetonyl sulfide and hydrogen chloride were used. A steady decrease in sulfenyl halide titer was indeed observed, indicating a reaction between I and the acetonyl sulfide, but the rate was far too slow to explain the increase in rate in Run 53* 112 TABLE XXXIX SUMMARY OP RUNS CARRIED OUT AT 50° WITH LIMITED AMOUNT OP ADDED ACID Run No. Init. ArSCl (m/1) Init. Acetone (m/1), Init. HC1 (m/1)} H K \ 1 H O • * k-^xlO Init Acetone 50 *114 .116 • .116 * * 51 .068 .068 .071 4.71 6.93 52 .06? .034 .034 2.02 5.94 .0677 .0665 .0665 5.98 9 *00 * This run was of intermediate (between first and second) order. ** Acetonyl sulfide added. Note: The values for k, x 10 divided by the sum of the initial acetone and hydrogen chloride concentrations were 3*39, 2.97 and 4.'50 for runs 51> 52, and 53, respectively 113 If all the substances present in the solution dur ing a run are considered, it appears reasonable that other substances capable of hydrogen bonding may be formed through the following equilibria. 1. ch3coch3 t > ch2=c($h )ch3 (VII) 2. CH3COCH3 + HC1* ■ ■ ■ ----» CH3C(=$H)CH3C1" (VIII) 3. CH3COCH3SAr + HC1* - --■ » CH3C(=$H)CH2SAr Cl” (IX) 4. ch3coch3 + hci* t....> ch3c(=oh)och3 Cl” (X) Thus, in addition to acetone enol and hydrogen chlo ride, the protonated forms of acetone, acetonyl sulfide, and methyl acetate are present and probably active in pro moting step one. Taking these substances into considera tion, equation 4 becomes: Equation 5. -d(ArSCl)/dt = (ArSCl) [k-^VIIl) + k2(VIl) + k3(IX) + k^(HCl) + k5(X)]. Terms should also be added for p-toluenesulfonie acid and for mercuric chloride for the runs in which these are present. Using the equilibrium constant expressions for reactions one to four, it is possible to express the values for the concentrations of VII, VIII, IX and X in terms of the concentrations of other species in the * Also p-toluenesulfonic acid when present. 114 solution: (VII) = Ke(CH3COCH3) (viii) = k1(ch3coch3)(hgi) (IX) = Ki j .(GH3GOCH2SAr)(HCl) (x) = k^(gh3coch3)(hci) = k5(hci) In deriving these it was assumed that the ionic species VII-X exist in the solution as ion pairs, rather than as free ions. This would he expected in a solvent of such low dielectric constant (7.3)^ as methyl acetate.2^ That reactions 2, 3, and 4 could occur, and that some ionization does occur, was shown by conductivity studies. The conductivity of pure methyl acetate, methyl acetate with anhydrous chloride, hydrogen chloride as well as acetone, and acetone alone added were compared. It was found that the conductivity of the solutions with added hydrogen chloride was significantly higher than those with no added acid, and that the conductivity increased with increasing hydrogen chloride concentration. When the above values for VII, VIII, IX, and X are substituted into equation 5, and the last two terms com bined, equation 5 becomes: 115 Equation 6. -d(ArSCl)/dt = (ArSCl) [k-^CCHgCOCH^ (HCl) + k2Ke(CH3COCH3) + k3K3(CH3COCH2SAr)(HCl) + (k4 + k5)k5(hci)] If this equation is to reduce to a first order ex pression (as is required by the data when no excess of acid : is present) it is necessary that the sum of the terms in brackets remain constant during the reaction. Considering each of these terms individually, it can be seen that the !first term will be zero at the beginning of the reaction, increase slowly to a maximum at 50 per cent reaction, and decrease slowly thereafter. The second terra will be at a f maximum at the beginning of the reaction and will decrease regularly thereafter. The third term, starting at a value i of zero, will increase exponentially, and the fourth term, also starting at zero, will increase linearly during the reaction. These relationships can perhaps best be seen from an equation in terms of a and x in which a is the initial acetone concentration and x is the amount of sulfenyl halide reacted. (It is assumed throughout that there is no ; 'storage1 of starting materials in the form of intermediates or protonated species.) Equation 6a. -d(ArSCl)/dt = (ArSCl) [k-jK^a-x.) (x) + k2K^(a-x) + k3K3(x)2 + k'(x)] i i 6 ' ■ Thus at the beginning of the run (when x is small) terms 1, 3* and 4 are increasing slowly, compensating for the decrease in term 2. In the latter half of the reaction, the value of term 1 is decreasing rather than increasing, helping to compensate for the now rapid increase in term 3* For those runs in which no acid is added, the initial rate (and, if the expression in brackets does indeed remain constant, the rate for the entire reaction) should depend on the initial acetone concentration, as is indeed ob served. This also allows the evaluation of k0K since the 2 e observed rate constant for these runs should equal k^Ke(a) — the value k2K~ being the proportionality factor between observed first order rate and initial acetone concentra tion discussed above. Its value (see Table XXXVII) is taken as 0.054, the average value for the runs made in sealed ampoules. For those runs in which a small amount of hydrogen chloride was added (the reaction remaining first order) the initial rate should be proportional to terras 1, 2, and 4 of equation 6, and the observed rate constant is as given by equation 7. The rate should therefore be greater than that calculated from the initial acetone concentration• alone, as is observed, but should not necessarily be pro portional to the sum of the acetone and hydrogen chloride concentrations. ... 117 Equation J. kQbs = k^K-^CHgCOCI^) (HCl) + 0.054(CH3C0CH3) + k^(HCl) By solving equation 7 for Runs 51 and 52 simultaneous ly it should be possible to evaluate k^K^ and k^. When this was done the values obtained were k^K^ = 0.302 and k^ ^ • • -0.005. The negative value found for k^ is, of course, im possible, and seems to indicate that equation 6 is not sat isfactory. However, in calculating these constants it was necessary to use the differences between numbers of very similar magnitude, and therefore even a relatively small er ror in the value for the concentrations or the observed rate constants could cause a very large error in the constants thus calculated. To evaluate and to demonstrate this error, the constants were recalculated using a value for the ob served rate constant for Run 52 which was 5 per cent higher than that obtained experimentally. The constants thus ob tained were: = 0-. 19 and k^ = 0.0018. As the probable 1 errors in the rate constants used are at least 5 per cent, and, in addition, there are probably errors in the con centrations used, it was apparent that accurate values for these constants could not be obtained in this manner. The evaluation of k3K3 from the data of Run 53 by similar means f' is subject to the same limitation. Therefore these values were not used except as a guide to the order of magnitude : 118 of the actual constants, which were estimated hy trial and error methods using the data of all of the first order rims (at 50°). At any point during any of the first order.runs, it should he possible to evaluate the rate constant from equation 8. Using different sets of arbitrary constants (except that they corresponded in order of magnitude to . the constants calculated from the data of Runs 51# 52, and 53) rate constants for each of the points in each of the first order runs were calculated and checked for constancy during the given run, and for correspondence to the constant calculated via the first order rate -'equation (and/or the constant calculated from the slope of the log. (ArSCl) vs. time plot). The best fit found was. for the set of constants = 0.15, ^3^3 = 0.20, and k^ = 0.018. Table. XL summarizes the results of the calculations using these constants. The average rate constants calculated with- , the aid of equation 8 deviated from the rate constants via the first order equation (-d( A r S C l)/dt= k(ArSCl)) by 5 per cent (average deviation). It can be seen that each set of rate constants remains fairly constant, although 1 most do have a decided tendency to increase or decrease steadily throughout the run. This tendency to drift may be due to a poor selection for the relative values for , the constants. It is interesting.tq_note,. however, that, TABLE XL FIT OF FIRST ORDER DATA TO EQUATION 8 " 1 ~ ........ ..— 1 .. —— ........ ‘ j1 ■ — x 102 at Each Point Calculated from Equation 8 *v®q2 ^ Rate Equation 51 5.67 5.41 5.23 0 0 • LA 0 CO • 4.74 4.64 CO LA • - = t * 5.01 4.71 + 6 52 2.62 2.57 2.34 2.18 1.95 1.86 2.25 2.02 +11 53 6.33 6.28 6.20 6.10 6.04 6.10 5.98 5.97 5.96 5.95 6.09 5.98 + 2 36 6.65 6.57 6.55 6.55 6.46 6.41 6.40 6.40 6.40 6.42 6.48 6.66 - 3 32 13.6 13.9 14.6 15.2 15.9 16.2 16.4 15.1' 14.7 + 3 33 14.6 14.9 15.1 15.3 15.8 16.0 15.3 14.9 + 3 31 7.35 7.04 6.72 6.49 6.40 6.35 6.27 6.24 6.23 6.57 7.35 -10 35 3-74 3.45 3.20 3.08 2.61 3.22 3.55 - 9 Average Deviation 5$ T2U in some cases at least (e.g. Runs 33* 3^* and 36) the trend in the rate constants calculated via equation 8 parallels the trend in rate constants calculated from the first order rate equation (see Tables LIII, LIV, and LVl). Some of the error in the values calculated from equation 8 is Undoubtedly caused by the use of uncorrected values for the acetone, hydrogen chloride, and acetonyl sulfide concentrations. For example, the value used for the acetone concentration was the.stoichiometrically calcu lated one, whereas the true acetone concentration is the stoichiometric concentration minus the concentrations of VII and VIII. Equation 8. kobg = (CH^COCH^) (HCl) Thus the data for the first order run fits, at least reasonably well, equation 8, which is derived from step 1 of Mechanism II. It should be noted that the fact that the first order rate constants obtained,using ethylene chloride and acetic acid - , a s solvents did not change when hydrogen chloride was added is not inconsistent with the above since, in these solvents, step 2 may be rate de termining even in the absence of acid; and, because of I the—large—exc-e.se_Q£—ac.e-t.one-jused., s_tep_2_-would als o give + k^K^ (CH^COCHgSAr)(HCl) + k^(HCl) .......... . .................... 1 12T~ pseudo-first order kinetics. Equation 8 does .not, however, explain the shift from first to second order kinetics observed when excess acid is added. It is necessary to assume that step 2 be- * comes rate determining under these conditions. That this is reasonable is indicated by the fact that, when acid is added, step 1, as is required by equation 8, increases in rate; and, if the two reactions are not too different in rate when no acid is present, step 1 may become faster than step 2. There should, of course, be a region of acid concentration where the two steps are of comparable rate, leading to intermediate order kinetics. This was observed in Run 50, the first part of Run 49* and in the study of the reaction of diethyl ketone with I (see be low) . Step 2 as the rate determining step would require second order kinetics — first order with respect to both acetone and I -- with the rate relatively independent of the amount of excess acid added, all of which is as ob served. The data do not allow us to decide whether the keto or enol form of acetone is reacting. In order to * Another possibility, suggested by the work of Szmant,°l is that the acid is promoting nucleophilic at tack by sulfur on acetone, by protonating the acetone. However, if this were so, the second order rate should be proportional to the acid concentration, which is not observed. _........................... ....... 122 determine whether or not the rate of enolization of ace tone in methyl acetate is rapid enough to permit the enol to participate, a study of the bromination of acetone in methyl acetate was made, for it has been shown that in this reaction it is the enol which reacts. It was found that, whether or not hydrogen chloride was present, the reaction between bromine and acetone in methyl acetate was complete within thirty seconds, indicating that the rate of conversion of keto to enol is extremely rapid, k run in which acetone was omitted showed that this rapid disappearance of bromine was not caused by attack on the solvent. When a small amount of quinoline was added, an induction period of eighteen minutes was observed; but complete reaction occurred during the nineteenth minute. This indicates that the conversion of keto to enol form of acetone occurs only slowly when no acid is present, but is very rapid in the presence of acid, in accord with the 1^ work of Cathcart. The fact that the enolization of acetone is ex tremely rapid under the conditions used in the sulfenyl chloride-acetone study means that the keto and enol forms of acetone are kinetically indistinguishable in the re action. To ascertain whether the rate of reaction of I with acetone enol might be of the proper order of magni tude, isopropenyl acetate was again used. The reaction between isopropenyl acetate and I in methyl acetate was found to be considerably slower than the corresponding acetone reaction. Unfortunately, satisfactory rate data could not be obtained because of the extensive decomposi tion occurring after about two hundred fifty hours (at which time approximately 40 per cent, reaction had oc curred). The exact, nature of the decomposition is not known but the reaction mixture apparently underwent alter nate reaction (darkening) — as observed in the Experi mental part. Nevertheless, because of the known reactivity of I -50 with olefins, and the well known tendency of ketone sub stitutions to occur through the enol form, it is believed likely that step 2 consists of attack of the sulfenium- chloride ion pair (or sulfenium ion) on the olefinic link age of acetone enol. The rate expression for step 2 would therefore be: Equation 9. dUrSCHgCOCH^)/dt = k(ArS+Cl~)[CH2=C(OH)CH3] When this step is rate determining in the reaction, the equilibrium of step 1 must be fast compared to it, and the ArS+Cl~ concentration may be expressed as: (ArS^Cl-) = K-^(ArSCl). Likewise it has been shown that the enolization of acetone is rapid compared to step 2, „-------------------------- . ------------------12-4“ so that the enol concentration may be expressed as: [CH2=C(0H)CH2) - K^CH^COCH^). When these are substituted into equation 9* equation 10 is obtained. The tendency for the rate to decrease with increasing acid concentra tion may be caused by a lowering.of the equilibrium enol concentration, caused by the increased conversion of ace tone to VIII by the excess acid. However, this effect is probably minor as compared to activity coefficient effects caused by added acid. Equation 10. d(ArSCH2COCH3)/dt = kK^K±(ArSCl)(CH^COCH^] There is, however, a major objection that can be raised to this interpretation of step 2 — namely its 4 . _ . relatively slow rate. The ArS Cl ion pair (or the sul'fenium ion itself) would be expected to be a highly i reactive intermediate (as it is, for example, in the aluminum chloride and sulfuric acid catalyzed Friedel- Crafts reactions of I with aromatic systems^) and thus it should react rapidly with acetone enol. Also, the re- 40 action of I with olefins is considerably>more rapid than step 2. These factors would seem to indicate that step , 2 should be considerably faster than is observed. However, step 2 consists of the reaction of two species which are at very low concentrations (both Kg and are almost certainly very small), and this should decrease the X23 observed, rate. The effect of surface on both the first and second order reactions was tested by carrying out runs in the presence of added glass helices. The first order reaction (see Run 54) was completely unaffected by the added sur face, but the second order rate (see Run 55) was signifi cantly increased. No explanation for this increase in rate is offered at the present time. No studies to test the effect on the reaction of added salt were made — al though attempts in this direction were made and are dis cussed in Part IV, Chapter VI. The effects of solvent change and their interpretation in terms of mechanism II are also discussed in Chapter VI. The effect of temperature on the rate and kinetic behavior of the reaction was also studied. Table XLI sum marizes the data for runs at temperatures other than fifty degrees. It was found that the reaction at thirty and forty degrees showed essentially the same kinetic behavior as at fifty degrees. The reaction with no added acid was first order, with the first order rate constants propor tional to the initial acetone concentrations, and the acid catalyzed reaction was second order. The second order rate constants obtained for the reaction at thirty degrees, however, varied significantly -- apparently as an inverse function of the acid strength. There was__ 126 SABLE XLI SUMMARY OE RUUS AS SEMPERASURES OTHER-SHAN 50° Run . Ho . Semp. °G. Init. ArSCl (m/1) Init. Acetone (m/1) Init.' Acid* (m/1) V xlO^-, hr."* ^2 ' (m/l)“J hr. 2 k^xlO Init. Acetonf 56: 40 .135 .135 ----- 3.62 . ----- 2.68 57 40 .136 .136 ----- 4.15 ----- 3.05 65 40 .197 .197 .235 ----- .075 ■----- 58 30 .141 .140 ----- 2.3 ----- 1.64 59 30 .260 .260 ----- 5.1 ----- 1.96 60 30 .198 .199 — ■ 3.7 ----- 1.86 61 30 .136 .202 ----- 4.2 ----- 2.08: 62 30 .135 .269 ----- 4.56 ----- 1.70 64 30 .197 .198 .109 ----- .060 ----- 65 30 .196 .197 .215 — __ .042 ---- 66 30 .107 .247 .29 ----- .023 ----- p-toluenesulfonic acid 127 also a decided tendency for those first order runs at thirty degrees in which a relatively high initial acetone concentration was used to deviate towards second order towards the end of the reaction. Presumably the point in acid strength at which a shift from first to second order kinetics occurs is lower at thirty than at fifty degrees. When an Arrhenius plot for the data for the first order runs was made (Fig. 8), a straight line, slope 2.28 x 1CK was obtained, corresponding to an activation energy of 10.5 kcal. The values plotted were the logarithms of the average values for kQbs/initial acetone concentration at each'temperature (see Table XLII). The slope (and thus the activation energy) was calculated from the runs at fifty and thirty degrees, sinee six and five runs respectively were made at these temperatures, and only two at forty degrees. Using the above value for the activa tion J energy, and the Arrhenius equation, k = Ae^~ AH*/RT)^ a value of 5.78 is obtained for log. A. Using the method 28 suggested by Frost and Pearson, ^ the entropy of activa tion is found to be -32.2 e.u. The reaction therefore has a relatively favorable energy of activation, but a very unfavorable entropy of activation — the entropy term being the chief reason for the slow rate. The existence of this large, unfavorable entropy term lends considerable support to the hypothesis that the first order reaction is 128 TABLE XLII SUMMARY OP DATA POR ARRHENIUS PLOTS First Order Data: Temp. ^xlO2 * k-^xlO2 1 xlO5 °C Init. Acetone Log. Init. Acetone T’ 30 1.85 .26717 3.300 40 2.87 .45788 3.195 50 5.41 .73320 3.096 2.58 .41160 3.247 Second Order Data: Temp. °0 Run 2 Ho. (m/l)”f hr. 1 Log. k2 xlO2 1 xlO3 T 30 65 4.2 .62325 3.300 40 63 7.5 .87506 3.195 50 41 14.3 1.15524 3.096 * Average values for the runs at each temperature (see Tables XXXVII and XLI). ** Only one run, a preliminary one (Run 50), was made at this temperature. 2.0' First Order Second Order * Plotted. .Log k + 3 1*0 a , 3.0 V0 130 an ionization process, since such an entropy term is char acteristic of an ionization process in a non-polar solvent / 42 \ (see R. G. Pearson for a discussion of this effect). When an Arrhenius plot for the second order runs was made (using runs— see Table XLII — selected because of their similar starting concentrations of I, acetone, and p-toluenesulfonic acid, a straight line, slope 2.61 x 10 , was obtained. The activation energy, log. A, and entropy of activation were calculated and described above and found to be 12.0 kcal., 7*23* and -25.8 e.u., re spectively. Again we find a relatively low activation energy and a highly unfavorable entropy, although the activation energy is higher and the entropy less unfavor able than was the case for the first order reaction. The higher activation energy for the second order process ex plains the above-mentioned tendency for the first order runs done at thirty degrees to deviate towards second order at relatively low acid concentrations -- for the second order rate, because of its higher activation energy, is affected more (slowed down more) by the drop in temperature than is the first order rate, and the two rates thus approach more closely. The highly unfavorable entropy of activation for this reaction, presumably step 2. at first appears surprising, especially since ionic character is lost in the reaction, which should be highly 131 favorable, entropywise, in the relatively nonpolar solvent used. However, when the probable intimate mechanism of step 2 is considered, it is seen that the initial product is probably the ion pair of protonated acetonyl sulfide and chloride ion: following and very rapidly established equilibrium. It is impossible to estimate the change in solvation entropy due to charge distribution in going into the above transition state, but it probably is not very favorable. It should be noted that the formation of the transition state in volves the formation of one particle from two, which should make the entropy negative. All in all, the values found for the activation energies and entropies do not ap pear to be inconsistent with the hypothesis that the first order reaction corresponds to step 1 in Mechanism II and the second order reaction to step 2. kinetic behavior of the I-aeetone reaction extended to the reaction of I with other ketones. A preliminary study OH + - * ArS Cl + CH2=CCH3 OH Cl" OH i l If OH u ± ArSCHgCOCH^ + HC1 The loss of ionic character probably occurs as a It was deemed of interest to see if the anomalous was therefore made of the reactions of I with acetophenone, diethyl ketone, and pinaeolone. A summary of the data ob tained is given in Table XLIII. Two runs were made using acetophenone in place of acetone -- one without added acid (Run 67) and one with added p-toluenesulfonic acid (Run 68). The run without added acid proved to be first order and only slightly faster (k0^s /initial ketone concentration = 0.062) than the corresponding acetone reaction (kQbs /initial ketone concentration = 0.054). The run with added acid was second order and the rate constant obtained, 0.141 (moles/ liter)-3' hr.-1, was almost identical to that obtained for the corresponding acetone reaction (see Run 41). Two runs (69 and 70) were made with diethyl ketone - with no added acid. The rate of the reaction was greater than the corresponding acetone reaction (half-life about thirty hours as compared to a calculated half-life of about sixty hours for the acetone reaction using similar con centrations) . The reaction did not plot either for first or second order; and was apparently of intermediate order. No further studies were made. One run in which pinaeolone was the ketone was at tempted (Run 71)* The reaction was extremely slow -- the half-life under the conditions used being about two months. Nevertheless,..satisfactory data .were obtained, and. it was _ 133 TABLE XLIII RATE RUNS AT 50° USING KETONES OTHER THAN ACETONE ; Ron No, Ketone Init • ArSCl (m/l) Init. Acetone (m/1) k^xlO^ hr."1 Init. 2 • , Acid* (m/l)” (m/l) hr.” : 67 Ac et ophenone . 204 .204 12.'62 .-; — ----- 68 Acetophenone .160 .159 .207 .141 69 Diethyl Ketone .218 .218 Intermediate Order 70 Diethyl Ketone .096 .096 Intermediate Order 71 Pinaeolone .158 ,158 ----- --- .0048 * p-toluenesulfonic acid found that the reaction plotted best for second order even though no acid was added. The first part of the second order curve was irregular, however, and an enlarged plot of the data for the first two hundred hours indicates that this part of the reaction is first order. This behavior is easily Interpreted on the basis of mechanism II, if one as sumes that the tertiary butyl group of pinaeolone, by its steric effect, decreases the rate of both step 1 and step 2 to about the same extent. The reaction at its beginning, should therefore be first order. However, as it proceeds, hydrogen chloride is produced, which catalyzes the first step. While the first three terms of equation 8 are de pendent on the nature of the ketone, and therefore pre sumably decreased by the tert-butyl group of pinaeolone, the fourth term is, of course, independent of the nature of the ketone and will therefore increase disproportion ately as hydrogen chloride is produced. Thus as the re action. proceeds the rate of step 1 should increase rapidly and it should overtake step 2 in rate, making the latter rate determining. Ill. EXPERIMENTAL 1. Preparation of Reagents. a. Methyl acetate was prepared by the reaction of methanol with acetic anhydride. A typical_preparation.was. as follows: Acetic.anhydride. _ . 135 (2130 ml., 22.5 moles) was placed in a five liter three- neck flask fitted with condenser, dropping funnel, and me chanical stirrer, and five ml. concentrated sulfuric acid added. The stirrer was started and methanol (806 ml., 20.0 moles) added dropwise from the dropping funnel at such a rate that the mixture was brought to gentle reflux by the heat of the reaction. After all the methanol was added, the stirrer was removed and the mixture refluxed for several more hours. The methyl acetate was removed by fractional distillation and purified by several fractional distillations from acetic anhydride. B,p. of accepted fraction, 57-1-57.2°. It was stored in glass stoppered flasks and dry nitrogen was bubbled through it for thirty minutes before use. b. Pyridine: Commercially obtained pyridine was dried with calcium hydride and stored over this reagent. £. Mercuric chloride: Baker’s C. P. mercuric chloride was oven-dried at 110° for two hours. d. 2,4-Dinitrophenyl 4'-dimethylaminophenyl sulfide: This substance was prepared by reaction of I with dimethylaniline in ethylene chloride, and recrystallized from absolute ethanol before use. < 2. Bromine: Commercial C. P. bromine was dried over phosphoric anhydride. f. Glass helices: _Glass helices (3/16 .in. in___ 136" diameter) were washed four times with distilled water, three times with acetone, and then oven-dried at 110° for four hours. g. Acetophenone: Commercially 'pure' material was fractionally distilled, the constant-boiling middle fraction being retained. h. Diethyl ketone: Same as for acetophenone, ( i above. ! jL. Pinaeolone: .A sample, kindly furnished by Mr., George Schmid was purified as described in part j; above. _j. All other materials used were prepared as de scribed in previous chapters. 2. Identification of Product and Study of Complete ness of the Reaction of 1 with Acetone in Methyl Acetate. A solution of 5,562 g. (0.0237 moles) I and 4.707 g. (0,0810. moles) acetone in 100 ml. methyl acetate was prepared and placed in the constant temperature apparatus at 50°. After eleven days, the solution gave a negative stareh- iodine test. The solvent and excess acetone were aspirated and the resulting yellow solid refluxed with 25 ml. of absolute ethanol. The mixture was chilled and the solid separated. It proved to be 5*67 g. (0.0221 moles — yield 93-3 pei1 cent) of 2,4-dinitrophenyl acetonyl sulfide, m.p. l40-l4l°. This product gave no depression in melting point with authentic acetonyl sulfide. 3* Titration of I in Methyl Acetate. A solution of I.503. I g. of 1 in 100.0 ml. methyl acetate was prepared. Pour 10.0 ml. aliquots were removed and placed in fragile- bottom ampoules. The ampoules were chilldd in a Dry Ice bath, sealed, and placed in the constant temperature ap paratus at 50°. Four 10.0 ml. aliquots of the remaining solution were titrated as described in Chapter II. After twelve hours, the ampoules were removed, individually, from the constant temperature bath, chilldd for five minutes in Dry Ice, broken open into the titration mixture and titrated. The results are given in Table XLIV. Pseudo Rate Run to Check Evaporation Losses. A solution of about 3.5 g. I in 150 ml. methyl acetate in a standard taper glass stoppered flask was placed In the bath at 50° and a series of ten 10.0 ml. aliquots were re moved and titrated during the next seven days. A slow, steady increase in titer from 0.01045 equiv., to 0.01140 equiv. was observed. 5. Preliminary Rate Studies. Solutions of the de sired amounts of I and acetone in 200.0 ml. of methyl acetate were prepared. Each of twelve or thirteen standard taper glass stoppered test tubes was filled (requiring. 138 TABLE XLLV THE TITRATION OE 2, 4-DINITROBENZENESTJLEENYL CHLORIDE IN METHYL ACETATE ArSCl ArSCl (Theory) Round 4. 4 eq.xlO^ eq.xlO 1 o 1- 6.407 6.497 101.1 2. 6.407 6.390 99.5 3. 6.407 6.548 102.0 4. 6.407 6.302 98.4 Aliquots in Sealed Ampoules: 1. 6.407 6.461 100.9 2. 6.407 6.442 100.3 3. 6.407 6.403 100.0 4. 6.407 6.398 99.9 about 15 ml.) with the solution, stoppered tightly, and placed in the constant temperature bath. At irregular time intervals, tubes were opened and 10.0 ml. aliquots removed and titrated, the remainder of the solution in the tube being discarded. In the later runs (Runs 28 to 30) the stoppers of the tubes were sealed with was. All glassware was dried at 110° for at least two hours before use. The results of the best of these runs are given in Tables XLVIII to LII. In most of the rims carried out in this manner, the data were too erratic and inconsistent for use in calculating rate constants. 6* Rate Studies without Added Acid. A solution con taining the desired amounts of I and acetone in 200.0 ml. methyl acetate was prepared. Aliquots (10.0 ml.;) were pipetted into each of thirteen or fourteen fragile-bottom ampoules (capacity about 20 ml.). The openings of the ampoules were plugged with cotton, and the ampoules were chilled for at least fifteen minutes in an acetone Dry Ice bath. They were then sealed and placed immediately in the constant temperature apparatus at 50°. Aliquots (10.0 ml.) of the remaining solution were then titrated to obtain the initial point. In the titrations of the solu tions in the ampoules, twenty seconds were allowed for the ampoules to drain after being broken into the titration 140 mixture. The ampoules were constructed in such a manner that most of the glass in contact with the solution broke away and fell into the titration mixture, so that a minimum of loss was entailed. Runs 31* 32, 33y 3^* and 35 were carried out in this manner. Run 36 was done in the same way except that 2.68 g. of 2,4-dinitrophenyl acetonyl sulfide (freshly recrystallized from ethanol) was added in making the mother solution. In Run 54 glass helices were placed to a depth of about 2 cm. ; in each of the ampoules used. In the other determinations,' the solution filled each ampoule to a depth of about 3 cm. 7* Runs with Excess Hydrogen Chloride Added. Runs 37, 38, and 39 were carried out exactly as described in 6 above, except that the methyl acetate used was chilled and anhydrous hydrogen chloride passed in before the sulfenyl chloride and acetone were added. The amounts of hydrogen chloride used (measured by weight difference) were 4.8 g., 3.3 g.* and 2.8 g. respectively. This corresponds to molarities in hydrogen chloride of O.65, 0.52, and 0.38 for the three runs respectively. The results are given in Tables IX to IXII. Possible Reaction of I with p-Toluenesulfonic Acid. A solution containing 1.888 g. (0.0804 moles) of I and 2.573 g. (0.100 moles) of p-toluenesulfonic acid in__.J 1.1 Run 35 OJ + 0.9 H 0 C O Soj a) ;a 1 . 0.7 ) I I j ! 0.3 200 150 100 Time (hrs.) FIGURE 9 142 100 ml. methyl acetate was prepared. Aliquots (10.0 ml.) ; of this solution were sealed into ampoules as described in 6 above and placed in the constant temperature bath at 50°. No regular decrease in titer was noted, and after : 167 hours the titer was still more than 97 per cent of the theoretical value. 9- Runs with Added p-Toluenesulfonic Acid. These were carried out as in 6, above, except that p-toluenesul- fonic acid was added to the mother solution. The results are given in Tables IXEII to LXXI. In Run 55 glass helices were placed in each ampoule ■ used as described in 6 above. Possible Reaction of _I with Mercuric Chloride. A ■ solution of 1.2 g. of I and 1.84 g. mercuric chloride in 100 ml. methyl acetate was allowed to stand at room tem perature for two days. No decrease in titer of the solu tion occurred during this time. 11. Rate Run with Added Mercuric Chloride. Run 49 was carried out as described in 6, above, except that 7-683 g- , (0.0274 moles) of mercuric chloride was dissolved in the methyl acetate used. The results are given in Table LXXII and Fig. 11. 12. Possible .Interaction, of. I with Pyridine,.A Run 45 0.6 0.5 oo 60 Time (hrs.) -P-IG-URS-1^0- 20 100 120 H - I—I o CO u <c a o H CO o ■o 0 150 200 100 Time (hrs.) FIGURE 11 145 solution of 3-035 g. (0.0129 moles) of I in 100.0 ml. methyl acetate was prepared. Eight fragile-bottom ampoules were dried for three hours at 120° and stoppered with dried corks. . To each of these ampoules in turn was added 0.15 ml. (pipette) dry pyridine and then, immediately, 10.0 ml. of the sulfenyl chloride solution. The ampoules were restoppered at once, placed in an acetone-Dry Ice bath for ten minutes, and then sealed and placed in the constant" temperature bath at 50°. After the ampoules had been in the Dry lee bath for about five minutes, a flocculent precipitate was noted in each of them. This precipitate did not dissolve when the ampoules were warmed to 50°, and is presumably mostly bis-(2,4-dinitrophenyl) disulfide. Several 10.0 ml. aliquots of the original sulfenyl chloride solution were titrated to obtain an initial point. Ampoules were removed from the constant temperature bath, chilled, and titrated at irregular time intervals during the next six days. The results of these titrations are given in Table XLV. The precipitate noted above persisted during this time, but did not appear to increase in amount after the first hour. 13• Interaction of 2,4-Dinitrophenyl 4'iDimethyl- aminophenyl Sulfide with I_. a. A solution of 4.10 g. (0.0174 moles) of I and 5-58 g. (0.0175 moles) of the 146 TABLE XLV APPARENT INTERACTION OP 2,4-DINITROBENZENESULFENYL CHLORIDE WITH PYRIDINE Time Hr. Equiv. ArSCl Pound 1. 0 0.01275 2. 1.17 0.00947 3. 24.5 0.00921 4. 46.5 0.00919 5. 71 0.00880 6. 98 0.00849 7. 121 0.00888 8. 145.75 0.00835 147 amino sulfide in about 200 ml. methyl acetate was prepared. Two 10.0 ml. aliquots were removed and titrated for sulfenyl halide content. Three 10.0 ml. aliquots were removed, sealed into ampoules as described above, and placed in the bath at 50.0°. To the remaining solution was added acetone (0.8 g., 0.014 moles) and two aliquots removed and titrated. Six more aliquots were then removed, sealed into ampoules j as described previously, and placed in the bath at 50°. The solutions in the ampoules were titrated during the next forty-eight hours. The data obtained are given in Table XLVI. Ra-fre Studies with Limited Amounts of Hydrogen Chloride Added. Runs 50, 51* and 52 were carried out as described in 6, above, except that the methyl acetate used was prepared as follows: A solution of hydrogen chloride in methyl acetate was prepared by bubbling dry hydrogen chloride gas into ice-cold methyl acetate. This solution was standardized by diluting aliquots (5.0 ml.) with distilled water and titrating with standard silver nitrate solution (using potassium chromate as indicator). A volume of this standard solution containing the desired amount of hydrogen chloride was taken and diluted to 200 ml, with methyl acetate. A fresh, standard hydrogen chloride solution was prepared for each of the runs carried out. 148 TABLE XLVI THE REACTION OF 2,4-DINITROBEN1 ZENESTJLFENYL CHLORIDE WITH ACETONE IN THE PRESENCE OP 2, 4-DINITROPHENYL 4*-DIMETHTLAMINOPHENYL SULFIDE' Time ArSCl Pound . eq. xlO Ampoules Containing Amino Sulfide and no Acetone: 1. 0 7.81 2. 0 7.86 3. 14.67 3.20 4. 23 1.85 5. 161 0.47 Ampoules Containing Both Amino Sulfide and Acetone: 1. 0 6.50 2. 0 6.51 3. 13 3.03 4. 21.25 1.42 5. 37 0.49 6 • 160 0.32 Run 51 0,2 Run 52 400 100 200 Time (hrs.) —R-IG-UR-E—12- vo 150 The data for these runs are given in Tables LXXIV to LXXVT. Run 53 was carried out as described above except that 3.422 g. (0.0134 moles) of aeetonyl sulfide was added to the solution used. The results of this run are given in Table 1XXVII. 15. Conductivity Studies. A 0.14 M solution of hydrogen chloride in methyl acetate was prepared and standardized as described in 14 above. Various solutions of acetone, hydrogen chloride, and mixtures of these were prepared in volumetric flasks, and their conductivities measured (at 25.0°) on a Jones-Bradshaw conductivity bridge. The data are given in Table XLVII. Since the cell constant, was not known, the donductivity values are only relative ones. However, the value of the cell constant is known to be between 0.5 and 2.0, and therefore the values given are within a factor of two of the actual conductivities. The author is indebted to Dr. C. I. Dulin for the use of the conductivity apparatus and for aid in making the measure ments . 16. Bromination of Acetone in Methyl Acetate. A so lution of 1.0 ml. bromine in 300 ml. methyl acetate was brought to 30° and divided by pipette, into three equal portions. Anhydrous hydrogen chloride was bubbled into the first solution and 1.0 ml. acetone added. The cherry- 151 TABLE XLVII CONDUCTIVITY DATA Temp*: 25«0° Solvent: Methyl Acetate Solution Conductivity 1. Pure Methyl Acetate 10"8 2* 0.34 M Acetone < 10“8 3. 0.07 M HC1 6.7 X 10~7 4. 0.14 M HC1 7.0 X 10~7 5. 0.07 M HC1 and 4.6 X 10"7 0.07 M Acetone 6 . 0.14 M HC1 and 6.6 X io-7 0.07 M Acetone 152 red bromine color of the solution began to fade immediately, and the solution was completely colorless within thirty seconds. -To the second portion of the solution was added 1.0 ml. acetone. The color began to fade almost as rapidly as in the first solution, and again a colorless solution was obtained within thirty seconds. The third portion of the solution was allowed to stand in a glass stoppered flask at 30°. Aliquots (10.0 ml.) were removed at irregular time intervals and their bromine content estimated by passing them into an acidified 0.2 N potassium iodide solu tion and titrating the iodine released. The titer dropped . only very slowly — less than 5 per cent in twenty hours. After this time, 0.5 ml. quinoline and then 1.0 ml. acetone were added. During the next eighteen minutes, no change was noted, but at about the beginning of the nineteenth minute the color began to fade, and within thirty seconds thereafter the solution was colorless. The colorless solution (in all three cases), on addition to acidified potassium iodide solution, failed to release iodine im mediately, showing that no bromine was present. A very slow release of iodine occurred, almost certainly due to the presence of bromoacetone (see Chapter V). 17. Reaction of I with Isopropenyl Acetate in Methyl , Acetate. A solution of 4.458 g. (0.0445 moles) of iso- j ; propenyl acetate and 10.479.g. (0.0445 moles) I in 200.0 ml; , methyl acetate was prepared. Aliquots (10.0 ml.) were j placed in sealed ampoules, as described in 6, above. Titraf i j I tion of these aliquots at irregular time intervals indi- ; i cated that the reaction was quite slow, especially at first] • — but that the rate of disappearance of I increased after j I about 250 hours. About 18 per cent reaction occurred in \ t ! . 130 hours, 43 per cent in 300 hours, and 86 per cent in ( s j j 575 hours. After about 300 hours it was noted that the j i ; i solution in the ampoules varied from light orange to dark ; j red in color. When two ampoules, one orange and one red, ; ! ' i f were titrated at about the same time, as much as 20 per j I i cent difference in titer was found -- the titer of the red 1 I samples being less than that of the orange. The data could I i j 1 not be fitted to either first or second order kinetics, ; j t J and no rate constants could be evaluated. j i 1 • I j 18. Rate Studies at Temperatures Other than 50°. j I These were carried out exactly as described in 6 and 9> I i i ; above, except that the ampoules were kept in constant tem- J i | | perature baths at temperatures other than 50°. Runs 56, 1 \ 57 and 63 (see Tables LXXVIII, LXXIX, LXXXV) were done J at 40°, and Runs 58 to 62 and 64 to 6.6;(see Tables LXXX to ! LXXXIV and LXXXVI to LXXXVIII) were done at 30°. 154 19. Rate Studies Utilizing Ketones Other than Acetone. a. Runs 67 and 68 (see Tables. LXXXIX and XC) were done as described in 6 and 9s above* respectively except that aceto - phenone was used in place of acetone. I d. Runs 69 and 70 (see Tables XCI and XCII, and Pig. 13) were done as described in 6 and 9, above* re spectively* except that diethylketone was used in place of acetone. < 3. Run 71 (see Table XCIII and Pig. 14) was done as described in 6* above* except that pinaeolone was used in place of acetone. ■ H D C O . u - I Run 70 o vo no • O O J H ♦ 200 100 Time (hrs.) FIGURE 1^ 155 1.20 1.18 1.16 160 4 - 0 8o 120 Time (hrs.) 200 22 r H 10 3000 2000 Time (hrs.) FIGURE 14 1000 157 Temp. : Solvent 50° : Methyl TABLE XLVIII Run 26 Init. Acetate Acetone Cone.: 0.1615 M Cone. Log. kl Time ArSCl ArSCl J . * 2 (hr.) xl02 Cone. xlO - i (m/1) + 2 hr.*"1 1* 0 16.286 1.21181 ---------- 2. 6 16.135 1.20176 1.56* 3. 44 12.398 1.09332 6.20 4. 46 11.959 1.07769 6.72 5. 115 7.453 .87233 6.80 6. 116.5 6.884 .83784 7.39 7. 144.5 6.196 .79211 6.69 8. 220 3.374 .52815 7.16 9. 220.25 3.573 .55303 6.89 Average rate constant 6.83 Omitted in calculating average rate constant. 158 Temp. : Solvent 50° : Methyl TABLE XLIX Run 27 Init. Acetate Acetone Cone.: 0.457 M Time (hr.) Cone. ArSCl xlO^ (m/1) Log. ArSCl Cone • + 2 kl xlO5- , hr. 1. 0 5.517 .74170 --- 2. 6.25 5.083 .70612 13.1 * 3. 18.75 3.444 .53706 25.2 4. 25.25 3.062 .48601 22.6 5. 47.5 1.666 .22011 25.3 Average rate constant 24.4 Omitted in calculating average rate constant. 159 Temp.: Solvent 50° : Methyl TABLE L Run 28 Init. Acetate Acetone Cone.': 0.403 M Cone. Log. kl Time ArSCl ArSCl X . (lit*.) xlO2 Cone. xlO2, (m/1)..... +2 hr.~ 1. 0 8.958 .95221 --------- 2. 2 8.768 .94290 11.5 * 3. 20 5.420 .73400 25.2 4. 26 5.190 .71517 21.0 5. 48 3.156 .49914 ’ 21.7 6. 68 2.790 .44560 17.2 Average rate constant 21.3 Omitted in calculating average rate constant. 160 TABLE LI Run 30 Temp*: 35° Init. Acetone Cone.: 0.524 M Solvent : Methyl Acetate Time (Kr.) Cone. ArSCl xl02 J (m/l) Log. ArSCl Cone . +2 kl xlQ^-, hr. 1. 0 9.848 .99334 --- 2. 1.25 9.523 .97877 26.8* 3. 20 7.458 .87262 13.9 4. 25.75 6.932 .84085 13.6 5. 48 4.902 .69041 14.5 6. 67*25 3.831 .58327 14.0 7. 79 3.496 .54361 13.1 8. 96.5 2.550 .40657 14.0 9. 121.5 1.709 .23267 14.4 • o H 162.5 1.091 .03767 13.5 163 1.103 .04269 13.'4 Average rate constant 13.8 * Omitted in calculating average rate constant. l6l TABLE LII Rim 29 Temp.s Solvent 50° : Methyl Init. Acetate Acetone Cone.: 0.128 M Time (hr.) Cone. ArSCl xlO^ (m/1) Log. ArSCl Cone. +2 kl xlO5- , hr. 1. 0 25.620 1.40859 --- 2. 77 19.710 1.29469 3.41* 3. 77.25 16.855 1.22673 5.42 4. 77.5 17.347 1.23922 5.03 5. 128.58 13.505 1.13050 4.92 6. 128.75 12.620 1.10106 5.50 7. 150.83 11.064 1.04391 5.57 . 8* 151 11.219 1.04995 5.47 Average rate constant 5.33 * Omitted in calculating average rate constant. 162 Temp.: Solvent 50° : Methyl Acetate TABLE LIII Run 54 Init. Acetone Glass helices Cone.; 0.135 M added. i Oone. Log. t Time ArSCl ArSCl (hr.) xlO2 Cone. ■ (m/1) +2 : ; 1. 0 13.480 1.12950 2. 28 11.140 1.04689 3. 28 11.000 1.04139 4. 51 9.780 .99034 5. 70.5 8.560 .93247 e- 142.5 4.940 .69373 7. 142.75 4.900 .69020 8. 167 4.100 .61278 9. 190.5 3.380 .52892 • o H 239.5 2.500 .39794 • H H 269 2.220 .34635 12. 310 1.800 .25527 13. 382.5 1.260 .10037 ! 14. 382.5 1.330 .12385 _ T f e n = 7.35 xlO hr., calculated from slope of first order plot 163 Temp.: Solvent 50° : Methyl TABLE LIV Ron 31 Init. Acetate Acetone Cone.: 0.137 M Cone. Log. kl Time ArSCl ArSCl X • z (hr.) xlO2 Cone. xlO2- , (m/1) + 2 hr. 1. 0 13.900 1.14328 --- 2. 25 11.760 1.07041 6.71 3. 48.75 9.200 .96379 8.48 4. 67.5 9.090 .95856 6.30 5. 68 9.160 .96190 6.14 6. 95.5 6.820 .83378 7.25 7. 118.5 5.580 .74663 7.71 8. 141.67 4.900 .69020 7.37 9. 167.75 3.510 .54531 8.21 10. 192.5 3.000 .47712 7.97 11. 216 . 2.820 .45025 7.39 Average rate constant 7.35 164 Temp.s Solvent 50° : Methyl TABLE LV Run 32 Init. Acetate Acetone Cone.:' 0.251 M Cone. Log. kl Time ArSCl ArSCl (hr.) xl02 Cone. xlO (m/l) +2 hr. 1. 0 25.200 1.40051 --- 2. 25.5 18.740 1.27277 11.5 3* 50 12.270 1.08884 14.‘ 4 4. 50.75 12.110 1.08314 14.4 5. 68.75 8.530 .93095 15.7 6. 69.25 8.710 .94002 15.3 7. 97.25 5.100 .70757 16.4 8. 119.75 3.840 .58433 15.7 9. 120.75 3.770 .57634 15.7 10. 142.75 2.760 .44091 15.5 11. 143.25 3.150 .49831 14.7 12. 168.75 2.430 .38561 13.9 13. 169.75 2.530 .40312 13.5 Average rate constant 14*7 165 Temp.: Solvent 50° s Methyl TABLE LVI Run 33 Init. Acetate Acetone Cone.: 0.269 M Cone. Log. kl Time ArSCl ArSCl J L * 2 (hr.) xl02 Cone. xlO (m/l) + 2 hr. 1. 0 13.400 1.13487 ---■ 2. 24.5 9.770 . ' ’ 98989 13.6 3. 24.75 9.600 .98227 14.2 4. 48 7.050 .84819 13.8 5. 73.8 4.780 .67943 14.3 6. 73.75 5.040 .70243 13.5 7. 99.5 3.190 .50379 14.6 8. 99.5 3.010 .47857 15.2 9. 117.5 2.090 .32015 16.0 10* 117.5 2.160 .33445 15.7 11. 144 1.260 .10037 16.5 12. 144 1.260 .10037 16.5 Average rate constant 14.9 166 Temp.s Solvent 50° : Methyl TABLE LVII Run 34 Init. Acetate Acetone Cone.: 0.070 M Cone. Log. kl Time ArSCl ArSCl J L * 2 (hr.) xlO^ Cone. XlO n Cm/1) +2 hr. 1. 0 14.045 1.14755 --- 2. 17.5 12.924 1.11140 4.76* 3. 39.25 11.893 1.07529 4.24 4. 66.75 11.357 1.05526 3.18 5. 114.25 9.183 .96298 3.72 6. 184.5 7.493 .87466 3.41 7. 184.5 7.440 .87157 3.45 8. 207.25 7.052 .84862 3.3 2 9. 207.25 7.424 .87064 3.08* 10. 256.25 6.727 .82782 2.87* • H. H. 256.25 6.727 .82782 2.87* Average rate constant 3.55 * Omitted in calculating average rate constant. '167 TABLE LVIII Run 35 Temp.: 50° Init. Acetone Gone.: 0.170 M Solvent: Methyl Acetate Time (hr.) Cone . ArSCl xlO^ (m/1) Log. ArSCl Cone. +2 kl xlO^-, hr. 1. 0 16.900 1.22788 ---• 2. 23 13.870 1.14208 8.59 3. 48.75 11.610 1.06483 7.70 4. 48*75 11.490 1.06032 7.92 5. 94 7.690 .88593 8.39 6. 94 7.700 .88649 8.36 7. 144.5 4.560 .65896 9.07 8. 144.5 4.660 .66839 8.92 9. 167.5 3.810 .58092 8.90 • o H 191 3.160 ' .49969 8.78 11. 191 3.260 .51322 8.62 • C \ ! H 239 2.320 .36549 8.31 13. 239 2.380 .37658 8.20 14. 264 2.060 .31387 7.97 15. 305.5 1.680 .22531 7.56 Average rate constant 8.38 168 Temp.: Solvent 50° : Methyl TABLE LIX Run 36 Init. Acetone Cone.: Acetate Init. ArSCHgCOCH^ Cone.: 0.123 M 0.0524 M Cone. Log. kl Time ArSCl ArSCl (hr.) xl02 Cone. xlO (m/1) + 2 hr. • 1 * . 0 12.192 1.08575 , -------- 2. 15.25 10.916 1.03806 7.20 3. 15.25 11.010 1.04179 6.64 4. 20.5 10.672 1.02825 6.46 5. 41 9.354 .97100 6.45 6. 62.25 8.590 .93399 5.61 : 7. 89.5 6.729 .82795 6.63 . 8. 110.5 6.041 .78011 6.37 9. 146.25 4.418 .64523 6.94 10. 169.5 3.665 .56407 7.09 ’ 11. 233 2.444 .38810 6.90 12. 239.75 2.292 .36021 6.97 ' Average rate constant 6.66 Temp.: Solvent 50 o : Methyl TABLE LX Run 37 Acetate Init. Acid Cone.' (HC1) : 0.65 M Time (hr.) Cone. ArSCl xlCr; (m/1) 1 (ArSCl) *2 ; i . hr. 1. 0 11.455 8.73 --- 2. 6.75 9.902 10.10 .203* 3. 20.5 8.310 12.03 .161 4. 20.5 8.489 11.78 .149 5. 25.25 7.929 12.61 .154 6. 45.75 6.559 15.25 .142 7. 67 5.952 16.80 .120 8. 67.67 5.674 17.62 .131 9. 94 4.925 20.31 .123 10. 115 4.405 22.70 .121 ♦ H H 151 3.767 26.55 .118 12. 174.25 3.277 30.52 .125 13. 237.5 2.281 43.84 .148 Average rate constant .136 * Omitted in calculating average rate constant* 170 TABLE LXI Run 38 Temp.: 50° Init. Acid Cone.: 0.52 M (HC1) Solvents Methyl Acetate Time (hr.) Cone. ArSCl xlO 2 (m/1) 1 (ArSCl) k2 (m/l)”^ hr. . 1. 0 13.659 7.32 --- 2. 22.75 9.363 10.68 .148 3. 23.25 8.974 11.14 .164 4. 31 8.147 12.27 .160 5. 44.5 7.158 13.97 .149 6. 57.5 6.183 16.17 .154 7. 72.25 5.540 18.05 .149 8. 95 4.865 20.56 .139 9. 119.5 4.002 24.99 .148 10. 144.67 3.413 29.30 .152 H H • 168.75 3.410 29.33 .130 12. 189.92 3.128 31.97 .130 13. 190.5 3.028 33.03 .135 14. 212.75 3.201 32.14 .112 Average rate constant .144 171 TABLE LXII Run 39 Temp,: 50° Init. Acid Cone.: 0.38 M ( HC1) Solvent: Methyl Acetate Time (hr.) Cone. ArSCl xlO2 (m/1) 1 (ArSCl) k2 (m/l)"J hr. ± 1. 0 20.065 4.98 --- 2. 4.5 18.029 5.55 .125* 3. 6.5 16.802 5.95 .149 4. 18.5 13.295 7.52 .137 5. 30.5 10.310 9.70 .155 6. 43.5 9.034 11.07 .141 7. 51 7.901 12.66 .150 8. 55.25 7.303 13.69 .158 9. 67.75 6.344 15.76 .159 • o H 91.83 5.827 17.16 .133 11. 139.5 4.217 23.71 .134 12. 196.5 3.069 32.58 .140 13. 260.75 2.079 48.10 .165* Average rate constant .146 Omitted in calculating average rate constant. 172 TABLE LXIII Bun 40 Temp. : Solvent 50° : Methyl Acetate Init. Acid Cone.: (p-ch3c6h4so3h) 0.06 M Time (hr.) Cone. ' ArSCl xlO2 (m/1) 1 k2 hr.'1 (ArSCl)' 1. 0 19.924 5.01 --- 2. 7.67 16.939 5.90 .115 3. 20.75 13.054 7.67 .127 4. 32.33 10.588 9.45 .137 5. 70 6.680 14.97 .142 6. 70.25 6.674 14.98 .142 7. 94 5.215 19.18 .151 8. 95.5 5.085 19.67 .153 9. 102.25 4.772 20.96 .156 10. 118 4.267 23.44 .: 156 11. 167 5.630 27.55 .135 12. 167 3.491 28.65 .141 13. 240.5 2.668 37.48 .135 14. 240.5 2.791 35.83 .128 15. 342.5 1.603 62.38 .167 16. 342.5 1.573 63.57 .171 Average rate constant .144 173 TABLE LXIV* Run 41 Temp.: Solvent 50° s Methyl Aeetate Init. Acid Cone.: ( p - c h 5 c 6 h 4 s o 3 h > 0.19 M Time (hr.) Cone. ArSCl xlO 2 (m/l) . 1 (ArSCl) k2 _ • (m/l) Hr. “1 1. 0 19.645 5.09 ---- 2. 8.25 15.530 6.44 .164* 3. 19.25 12.840 7.79 .140 4. 33.25 10.360 9.65 .137 5. .50.08 8.310 12.03 .139 6. 70.5 6.780 14.75 .137 7. 70.5 6.850 14.60 .135 8. 95.5 5.290 18.90 .145 9. 119.75 4.490 22.27 .143 • o H 119.75 4.560 21.93 .141 n . 162.75 3.450 28.99 .147 12. 162.75 3.470 28.82 .146 13. 214 2.650 37.74 .153 14. 263 2.170 46.08 .156 Average rate constant .143 Omitted in calculating average rate constant* 174 TABLE LXV Run 42 Temp.: 50° Init. Acid Cone.: 0.14 M (p-ch3c6h4so5h) Solvent: Methyl Acetate (Time (hr.) Cone. ArSCl xl02 Cm/1') Cacetone) L°g. r^ g6Ty k2 (m/l)"? hr. 1. 0 9.875 .30005 --- 2. 6.75 7.780 .35478 .190 3. 19 5.380 .45134 .187 4. 19.5 5.250 .45824 .190 5. 24.25 4.590 .49715 .190 6. 30.5 3.830 .55224 .194 7. 43.88 2.600 .67950 .203 8. 46 2.690 .66785 .187 9. 46 2.660 .67168 .189 10. 54.5 2.160 .74436 .191 H H . 54.5 2.190 .73946 .189 • CM H 67.5 1.610 .85160 .191 13. 95.5 1.130 .98673 .168 14. 95.5 1.110 .99370 . .170. Average rate constant .190 H H 175 TABLE LXVI Run 43 Temp.: Solvent 50° : Methyl Acetate Init. Acid Cone. ( p - c h 3 c 6 h 4 s o : 0.13 M 5 h ) Time (hr.) Cone. ArSCl xl02 (m/l) T__ (acetone) Log. (ArSCi) k2 hr. 1. 0 19.450 - .29731 --- 2. 5 17.540 - .34602 .235 3. 17.25 14.520 - .46412 .232 4. 17.75 14.780 - .44976 .206 5. 22.5 13.770 - .51187 .228 6. 28.75 13.150 - .56057 .219 7. 42.13 11.930 - .69644 .227 8. 44.75 11.780 - .71997 .226 9. 44.75 11.670 - .73969 .237 H O . 53 11.140 - .84275 .246 11. 53 11.230 - .82249 .237 12. 65.75 10.400 -1.08255 .287* 13. 93.5 9.900 -1.43938 .292* 14. 93.5 9.760 -1.64705 .345* Average rate constant .229 I Omitted in calculating average rate constant. 17 6 TABLE LXVII Run 44 Temp.: Solvent 50° : Methyl Acetate Init* Acid Cone.: (p-ch3c6h4so5h) 0.115 M. Time (hr.) Cone. ArSCl xlO2 (m/l) - t (acetone) L°S- U r SCI)' k2 (m/l)“l hr. x 1. 0 19-75 -.29904 -- 2. 6.75 17.47 -.35922 .209 ; 3. 21 14.94 -.46597 .185 4. 21 14.64 -.48333 .206 5. 30 13.54 -.56225 .206 6. 30 13.71 -.54921 .195 7. 45.5 12.29 -.69854 .206 8. 45.5 12..23 -.70730 .210 9. 54.5 11.61 -.81446 .222 10-. 54.5 11.59 -.81844 .223 Average rate constant .207 177 TABLE LXVIII Run 45 Temp.': Solvent 50° : Methyl Acetate Init. Acid Cone. (p-ch3c6h- 4so : 0.116 M 3h) Time (hr;*4 ) Cone. ArSCl X1Q2 ____(m/l) . - . (acetone) log. -^fsciy k2 . (m/l)"?- . hr. 1. 0 4.925 , .30449 --- 2. 5 4.488 .32531 .192* 3. 19 3.755 .36791 .154 4. 19 3.723 .36996 .159 5. 28.5 3.345 .39724 .150 6. 44 2.851 .44012 .142 7. 66.5 2.209 .51388 .145 8. 66.5 2.236 .51028 .142 9. 67.25 2.203 .51468 .144 10. 92 1.690 .59780 .147 11. 119 1.302 .68511 .147 Average rate constant .148 Omitted in calculating average rate constant. 178 TABLE 1XIX Run 46 Temp.: Solvent 50° : Methyl Acetate Init. Acid (p-ch3c Cone•: 0.12 M 6h4s°5h) Time Gone. ArSCl 1 k * 2 (hr.) xl0,2 (m/l) (ArSCl) (m/l) $ hr. 1. 0 19.720 5.07 --- 2. 9.25 14.910 6.71 --- 3. 22.25 11.230 8.91 --- 4. 29.25 9.600 10.42 .216 5. 29.25 9.590 10.43 .218 6 . 49 6.920 14.45 .207 7. 49 6.930 14.43 .207 8. 72 5.140 19.46 .212 9. 72 5.190 19.27 .208 10. 95.5 4.080 24.51 .213 11. 119.5 3.550 28.17 .198 12. 163.5 2.440 40.98 .227 13. 163.5 2.'4 50 40.82 .226 Average rate constant .213 * Rate constants calculated from average of third and fourth points. 179 TABLE LXX Run 47 Temp.: Solvent 50° : Methyl Init. Acid Cone.: (p-CH^C.H.S0,H) Acetate p ° p 0.245 M Time (hr.) Cone. ArSCl xlO2 (m/l) 1 (ArSCl) l r * ' 2 ( m/l) hr. 1. 0 19.120 5.23 ----- 2. 4.5 17.120 5.84 ----- 3. 17 13.040 7.67 --- 4. 17 12.930 7.73 --- 5. 24 11.350 8.81 .159 6. 24 11.380 8.79 .155 7. 44 8.280 12.08 .162 8. 44 8.330 12.01 .159 9* 67 6.320 15.82 .162 H O ♦ 67 6.420 15.58 .158 11. 90.5 5.060 19.76 .164 • CM H 115 4.230 23.64 .163 13. 161 2.970 33.67 .180 Average rate constant .160 * Rate constants fourth, points. calculated from average of third and 180 TABLE LXXI Run 48 Temp.: Solvent 50° : Methyl Acetate Init. Acid Cone. (p-ch3c6h4so : 0.12 M 3H) Time Cone. ArSCl 1 k2 (hr.) xlO2 (m/l) (ArSCl) (m/l)-* hr. x 1. 0 10.010 9.99 --- 2. 6.75 8.915 11.22 .182 3. 20 7.620 13.12 .157 4. 20 7.800 12.82 .142 5. 47 5.985 16.71 .143 6. 47 5.970 16.75 .144 7. 72 5.065 19.74 .135 8. 118.75 3.510 28.49 .156 9. 118.75 3.560 28.09 *152 • o H 169 2.615 38.24 .167 • H H 169 2.680 37.31 .162 12. 224.25 2.050 48.78 .173 13. 239 1.905 52.49 .178 . H. 239 1.895 52.77 .179 Average rate constant .159 ! 181 Temp,s Solvent TABLE Run 50° : Metijyl Acetate LXXII 49 Init. Acid Cone (Hgci2) .: 0.14 M Time .... (hr.) Cone. ArSCl xlO^ (m/1) * 1 (ArSCl) ; 1. 0 10.190 9.81 2. 14 9.315 10.74 3. 14 9.395 10.64 4. 41 7.825 12.78 5. 41 7.835 12.76 6. 65.5 6.245 16.01 7. 112 4.545 22.00 8. 112 4.515 22.15 9. 163 3.295 30.35 • o H 163 3.325 30.08 H H • 217.75 2.480 40.32 12. 233 2.345 42.64 13. 233 . 2.385 41.93 182 TABLE LXXIII Run 55 Temp* j Solvent 50° : Methyl Acetate Init. Acid Cone.: 0.12 M (p-ch3c6h4so3h) Glass helices added. Cone. k0 Time ArSCl 1 ; d . — 1 (hr.) xlO2 (ArSCl) (m/l) n .... (m/1) . . . _ hr. 1. 0 19.900 5.03 — 2. 23 9.250 10.81 .252* 3. 23 8.710 11.48 .281 4V 31.25 7.070 14.14 .292 5. 42.5 5.650 17.70 .299 6. 42.5 5.660 17.67 * .298 7. 114.25 2.730 36.63 .277 8. 114.25 2.580 38.76 . 296 9. 139 2.180 45.87 .294 10. 162.5 . 1.910 52.36 .292 Average rate constant .291 Omitted in calculating average rate constant* 183 TABLE LXXIY Run 50 Temp.: 50° Init. Acid Cone.: 0.10 M (HC1) Solvent: Methyl Acetate Init. Acetone Cone. : 0.116 M • Time (hr. X Cone. ArSCl xlQ^ . (m/l)) Log. ArSCl Cone. +2 1 (ArSCl) 1. 0 11.423 1.05778 8.75 2. 12 8.820 .94547 11.34 3. 12 9.010 .95472 11.10 4. 26 7.530 .87680 13.28 5. 26 7.720 .88762. 12.95 6. 49 6.800 .83251 14.71 7. 49 6.740 .82866 14.84 8. 82.75 5.080 .70586 19.69 9. 126 3.920 .59329 25.51 H O • 126 3.960 .59770 25.25 ' 11. 196 3.020 .48001 33.11 12. 196 2.980 .47422 33.‘ 56 13. 274.62 2.740 .43775 36.50; 184 TABLE LXXV Run 51 : Temp.: 50° Init. Acid Cone.: 0.071 M (HC1) Solvent: Methyl Acetate Init. Acetone_Cone.: 0.068 M Time (hr.) Cone. ArSCl xi02 (m/l) Log. ArSCl Cone. ' +2 kl xlO^-, hr. 1. 0 6.780 .83122 --- 2. 23 6.000 .77815 5.31 3. 23 6.100 .*78533 4.60 4. 77.17 4.690 .67117 4.78 5. 77.17 4.720 .67394 4.69 6. 142.5 3.520 .54654 4. 60 7. 144 3.500 .54407 4.59 8. 215 2.470 .39270 4.70 9. 264 2.100 .32222 4.44 10. 360 1.570 .19590 4.06* 11. 360 1.460 .16435 4.27* 12. 478.5 1.210 .08279 3.60* Average rate constant 4.71 Omitted in calculating average rate constant. 185 TABLE LXXVL Run 52 Temp*: 50° Init,; Acid Cone.: 0.034 M ( HC1) Solvent: Methyl Acetate Init. Acetone, G o n e 0.034 M Time (hr.); . Cone.1 ArSCl ................ xlO^ . (m/1) Log.' ArSCl Cone.' +2 kl xlO3 hr."*1 1. 0 6.685 .82237 --------- 2. 17 6.430 .80821 1.92 5. 17 6.510 .81358 1.19 4. 71.6 5.700 .75587 2.14 5. 137 5.030 .70157 2.03 6 • 137 5.090 .70672 1.94 7. 209.5 4.290 .63246 2.09 8. 259 3.940 .59550 2.02 9. 354.5 3.520 .54654 1.79* H O • 547.-5 2.990 . .47567 1.46* Average rate constant 2.02 Omitted in calculating average rate constant* 186 TABLE LXXVII Run 53 Temp.: 50° Init. Acid Cone.r 0.0665 M Solvent: Methyl Acetate Init* Acetone Cone.: 0.0665 M Init** ArSCHgOGCEj Cone.: 0.066 M Time (hi*.) . Cone. ArSCl xl02 (m/1) Log. ArSCl Cone. +2 1. 0 6.765 .83027 2. 21.5 6.180 .79099 3. 46.5 5.369 .72591 4. 88 4.050 .60746 5* 88 4.070 .60959 6. 136.5 3.070 .48714 7. 136.5 2*980 .47422 8. 161.5 2.650 .42325 9. 195.5 2 J210 .'34439 H O • 236.25 1.940 .28780 11. 236.25 1.870 .27184 12* 281 1.580 .19866 13. 335.5 1.360 .13354 14. 429.5 1.080 .03342 15. 429.5 1.070 .02938 kl = 5.98 xl0“^ hr.71 plot calculated from slope of first order 187 Temp.: Solvent 40° : Methyl TABLE LXXKEII Run 56 Init. Acetate Acetone Cone.':' 0.135 M Time (hr.) Cone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +2 l r ^ 1 xlO5- , hr. 1. 0 13.460 1.12905 --- 2. 29.5 12.230 1.08743 3. 29.5 12.140 1.08422 --- 4. 74 10.440 1.01870 3.47 5. 74 10.350 1.01494 3.67 6. 146 8.050 .90580 3. 55 7.' 241 5.420 .73400 3.83 8. 241 5.730 .75815 3.57 9. 337.25 3.790 .57864 3.80 10. 337.25 3.770 .57634 3.69 H H • 434 2.800 .44716 3.64 12. 530 2.030 .30750 3.58 13. 648.5 1.770 .24797 3.12** 14. 842.5 1.350 .11561 2.75** Average rate constant 3.62 * Rate constant calculated from average of second and third points* ** Omitted in calculating average rate constant. 188 TABLE LXXIX Ran 57 Temp*: o o Init. Acetone Cone.: 0.136 M Solvent : Methyl Acetate Cone. Log. Time ArSCl ArSCl (hr.) xlO* Cone. Cm/l) +2 1. 0 13'. 670 1.13565 2. 47 11.840 1.07335 5. 118.5 9.230 .96520 4. 169 7.390 .86864 5. 245 5.240 .71933 6. 245 5.280 .76343 7. 288.5 4.’ 410 .64444 8. 330 3.750 .57403 9. 378.5 3.070 .48714 H O * 438 2.550 .40654 11. 523 2.090 .32015 12. 523 2.120 .32634 13. 577.25 1.920 .28330 —3 —1 = 4*15 xlO hr., calculated from slope of first order plot. 189 Temp. : Solvent 30° : Methyl TABLE LXXX Run 58 Init. Acetone Cone.: Acetate 0.140 M Time (hr.) Cone. ArSCl xlO^ (m/l) Log. ArSCl Cone. + 2 kl xlO^-, hr. “ 1. 0 14.145 1.15059 --- 2. 47.75 12.670 1.10278 2.31 : 3. 112.75 11.250 1.05115 2.03 4. 184.25 9.520 .97864 2.15 5. 208.25 8.870 .94792 2.24 6. 256.75 7.890 .89708 2.27 ; 7. 330.75 6.150 .78888 2.52 8. 432.75 4.800 .68124 2.50 9. 449.75 4.720 .67394 2.44 10. 570.5 3.680 .56585 2.36 H H • 714.75 2.650 .42325 2.34 12. 858.25 2.210 .34439 2.16 13. 858.25 2.250 .35218 2.14 Average rate constant 2#29 190 Temp.: Solvent 50° : Methyl TABLE LXXXI Run 59 Init. Acetate Acetone Cone.: 0.260 M Cone. Log. kl Time ArSCl ArSCl (hr.) x1Q2 Cone. xlO (m/l) +2 hr. 1. 0 26.080 1.41633 ----- 2. 46 21.830 1.33905 3.87 3. 111 15.720 1.19645 4.56 4. 182.5 9.760 .98945 5.39 5. 190.75 9.190 .96332 5.47 6. 206.5 8.330 .92065 5.53 7. 255 7.590 .88024 4.84 8. 256.25 7.320 .86451 4.96 9. 329 6.740 .82866 4.11* • o H 431 4.480 .65128 4.09* • H H 448 4.840 .68485 3.76* 12. 571.5 4.010 .60314 3.28* 13. 713 1.720 .23553 3.81* Average rate constant 5.12 Omitted in calculating average rate constant. I 191 TABLE LXXXII Run 60 Temp. 30° Init'.'1Acetone Cone.: 0.199 M Solvent : Methyl Acetate Cone. Log. k,** Time ArSCl ArSCl J L r t (hr.) xl02 Cone. xlO i (m/IT +2 hr. 1. 0 19.780 1.29623 --- 2. 43.67 17.510 1.24329 --- 3. 160.75 12.110 1.08314 --- 4. 160.75 12.170 1.08529 --- 5. 209.25 10.120 1.00518 3.75 6. 258.25 8.140 .91062 4.10 7. 329 6.420 .80754 3.79 8. 329 6.490 .81224 3 .'7 2 9. 474.58 3.670 .56467 3V81 10. 474.58 3.740 . 57287' 3.75 H H • 568.-75 3*000 .47712 3.43 12. 734.33 2.095 .32118 3.07* Average rate constant 3.76 Omitted in calculating average rate constant, ** Rate constant calculated from average of third and fourth points. 192 Temp.; : ; Solvent 30° : Methyl TABLE LXXSIII Run 61 Init. Acetate Acetone Cone.: 0.202 M Time (hr..). . Cone. ArSCl xlO^ (m/1) Log. ArSCl Cone. +2 v ** *1 xlO'L hr. 1. 0 13.567 1.13248 --- 2. 70 11.090 1.04493 --- 3. 70 11.035 1.04277 --- 4. 286.25 5.080 .70586 3.60* 5. 286.25 5.005 .69940 3.67* 6. 409 2.670 .42651 4.19 7. 429 2.405 .38112 4.25 8. 429 2.655 .42406 3.98 9. 502 1.735 .23930 4.29 10. 502 1.635 .21352 4.42 • H H 623 1.055 .02325 4.25 12. 623 1.000 .00000 4.35 13. 647.5 0.965 -.01547 4.22 Average rate constant * Omitted in calculating average rate constant. 4.25 ** Rate constant calculated from the average of the third and fourth points. 193 1 Temp.: Solvent 30° : Methyl TABLE LXXXIV Run 62 Init. Acetone Acetate Cone.: 0.269 M Cone. Log. Time ArSCl ArSCl (hr.) xl02 Cone. (m/1) +3 : 1« 0 13.480 2.12969 2. 71 9.590 1.98182 3. 71 9.530 1.97909 4. 244.5 2.840 1.45332 5. 244.5 2.870 1.45788 6. 288 2.140 1.33041 7. 288 3.240 1.51055 8. 413.5 .860 .93450 9. 413.5 .950 .97772 10. 461.5 .720 .85733 H H • 461.5 1.180 .07188 12. 527 .690 .83885 13. 527 .650 .81291 —3 —1 = 4.56 xlO hr., calculated from slope of first order plot. TABLE LXXXV Run £ j > 3 Temp.: 40° Init. Acid Cone.: 0.<235 M Cp-ch5c6h4so5h3 Solvent: Methyl Acetate Time (hr.) Cone. ArSCl xlO2 (m/1) . 1 (ArSCl), 1. 0 19.660 5.09 2. 22 15.390 6.50 3. 22 14.930 6.70 4. 47.25 11.620 8.'61 5. 72.25 9.765 10.24 6. 119.08 6.825 14.65 7. 119.08 7.355 13.60 8. 119.92 6.990 14.31 9. 168 5.570 17.95 • o H 286.5 3.710 26.95 11. 480.5 2.785 35.91 k2 = 0.075 order plot (m/l)"^ hrT^ • calculated from slope of second 195 TABLE LXXXVI Run 64 Temp.: Solvent 30° : Methyl Acetate Init. Acid Cone.: (p-ch3c6h4so5h ) 0.109 M Cone. k2 Time ArSCl 1 / —l (hi*.) xlO2 (ArSCl) (m/1.)-. (m/1) hr. 1. 0 19.720 5.07 ----- 2. 71.5 10.890 9.18 .058 3. 85 9.900 10.10 .059 4. 85 9.920 10.08 .059 5. 121 7.900 12.66 .063 6. 121 8.120 12.32 .060 7. 157.08 6.680 14.97 .063 8. 157.08 6.560 15.24 .065 9. 208 5.520 18.12 .063 H O • 257 4.740 21.10 .062 H H • 328.75 4.060 24.63 .060 12. 328.75 3.980 25.13 .061 13. 473.33 2.710 36.90 .067* Average rate constant .061 Omitted in calculating average rate constant. 196 TABLE LXXXVII Run 65 Temp.: Solvent 30° : Methyl Acetate Init. Acid Conc.r (p-ch5c6h4so5h) 0.215 M Time Cone. ArSCl 1 k2 (hr. ) • xlO2 (m/l) (ArSCl) (m/l) hr. x 1. 0 19.550 5.12 --- 2. 64.5 12.975 7.71 .040 3. 64.5 13.065 7.65 .039 4. 165.08 8.405 11.90 .042 5. 166.25 8.255 12.11 .042 6. 281.5 5.770 17.33 .043 7. 281.5 5.895 16.96 .042 8. 403.5 4.480 22.32 .043 9. 423.5 4.445 22.50 .041 H O • 617.5 3.080 32.47 *044 11. 642 3.040 32.90 .043 • CM H 642 2.900 34.48 .046 Average rate constant .042 197 Temp.: Solvent TABLE LXXXVTII Run 66 30° Init 'Methyl Acetate . Acid Cone.: 0.29 M ( p - c h 3 c 6 h 4 s o 3 h ) Time (ki*.) Cone. ArSCl xl02 Cm/1) Tn_ (acetone) Log. (j^sciy ' 1. 0 10.670 .36489 2. 66. 5 , 7.290 .46647 ■ 3. 66.5 7.380 .46295 4. 241 3.320 .71866 5. 241 3.330 .71760 6. 284 2.960 .75941 7. 284 3.120 .74062 ' 8. 409 2.010 .90255 9. 409 2.130 .88060 H O * 457 1.690 .96915 .11. . . 522.67 1.850 .93426 kg = 0.023 (m/l)”^ hr. 7^ calculated from slope of second order plot. 198 TABLE LXXXIX Run 67 Temp.: 50 o Init.1Aeetophenone Cone.1 : : 0.204 M Solvent : Methyl Acetate Time (.hr..) . Gone. ArSCl xlO2 (m/1) Log. ArSCl Cone. +2 kl xlO5- , hr. 1. 0 20.405 1.30974 --- 2. 7.25 17.970 1.25455 17.5* 3. 20.25 15.880 1.20085 12.4 4. 31.5 13.970 1.14520 12.0 5. 31.5 13.920 1.14364 12*1 6. 49 11.010 1.04179 12.6 7. 49 10.910 1.03781 12.8 8. 69 8.030 .90472 13.5 9. 69 8.180 .91275 13.3 10. 101 5.500 .74036 12.9 11. 127.3 4.270 .63043 12.3 12. 127.5 4.270 .63043 12.3 13. 166 3.460 .53908 10.7* 14. 166 3.440 .53656 10.7* Average rate constant 12**6 Omitted in calculating average rate constant• 199 TABLE XC Run 68 Temp.: 50° Init. ' Acetophenone Cone.: 0.159 M Solvent : Methyl Acetate Init. Acid (p-ch3c Cone.: 0.207 M 6H43()5H) Time (hr.) Cone. ArSCl xlO2 (m/1) 1 (ArSCl) k2 (m/D-ij- hr. 1. 0 15.980 6.26 --- 2. 4.25 14.270 7.01 .177 * 3. 4.25 14.280 7.00 .175 * 4. 22.5 10.720 9.33 .136 5. 22.5 10.680 9.36 .138 6. 45.5 7.880 12.69 .141 7. 92.25 5.040 19.84 .147 8. 92.25 5.010 19.’ 96 .149 9. 141.25 3.960 25.25 .135 • o H 141.25 3.840 26.04 .140 11. 213 2.750 36.36 .141 12. 213 2.-620 38.17 .150 13. 292.25 2.170 46.08 .136 14. 292.25 2.120 47.17 .140 Average rate constant .141 Omitted in calculating average rate constant. 200 Temp.s Solvent 50° : Methyl TABLE XCI Run 69 Init.; Diethyl Acetate Ketone Cone*’ : 0.218 M Time ( hr.) Cone-. ArSCl xl.O2 (m/l) Log. ArSCl Cone.* +2 1 ('ArSCl) 1* 0 21.810 1.33866 4.*59 2. 14.25 14.990 1.17580 6.67 3. 14.25 15.410 1.18780 6.49 4. 25.5 11.860 1.07408 8.43 5. 25.5 11.940 1.07700 8.38 6. 43 8.310 .91960 12.03 7. 43 8.520 .93044 11.74 8* 63.5 5.970 .77597 16.75 9* 63.5 5.860 .76790 17.06 H O • 95 4.040 .60638 17.75 11. 95 3.960 .59770 25.25 12. 121.5 3.100 .49136 32.26 13. 121.5 3.060 .48572 32.68 14. .160 2.340 .36922 42.74 15. 160 2.330 .36736 42.’ 92 201 Temp.: Solvent 50° : Methyl TABLE XCII Run 70 Init.' Diethyl Acetate Ketone Gone.: 0.096 M Cone . Log.' Time ArSCl ArSCl ; 1 ! (hr.) xlO2 Cone. (ArSCl) (m/1) +2 1. 0 9.590 .98181 10.47 2. 24 7.460 .87274 13.41 3. 24 7.450 .87216 13.42 4. 48 6.190 .79169 16.16 5.. 48 6.200 .79239 16.13 6. 78.5 4*840 .68485 20.66 7. 99.83 4.230 .62634 23.64 8. 99.83 4.230 .62634 23.64 9. 144.75 3.120 *49415 32.05 • o H 144.75 3.190 .50379 31.35 ii. 197.5 2.430 .38561 41.15 12. 197.5 2.440 . .38739 40.98 202 TABLE XCIII Sun 71 Temp.: 50° Init.- Pinaeolone Cone, r 0.158 M Solvent: Methyl Acetate Time ( hr.) Cone. ArSCl xl02 C m/1) Log. ArSCl Cone. +2 1 (ArSCl) 1. 0 15.800 1.‘ 200 50 6.32 2. 25.75 15.190 1.18156 6.58 5. 49 15.240 1.18298 6.56 4. 96 14.910 1.17348 6.71 5. 145 14.610 1.16465 6.84 6. . 216 14.040 1.14737 7.12 7. 487.75 12.030 1.08027 8.31 8. 1176.75 8.510 .92993 11.75 9. 1802.25 6.730 .82802 14.86 • o H 2378.75 5.640 .75128 17.73 H H • 3173 4.670 .66932 21.41 CHAPTER V THE REACTION OF 2,4-DINITROBENZENESULFENYL BROMIDE WITH ACETONE I. INTRODUCTION It has already been reported by Strashun. that the reaction bf 2,4-dinitrobenzenesulfenyl bromide (II) with acetone was not similar to that of the corresponding sulfenyl chloride. He found that II, in boiling acetone, was converted chiefly to the disulfide; only a small amount (about 10 per cent) being converted to the aeetonyl 67 sulfide. Zincke and Rose made similar observations in the case of the reaction of 4-methyl-2-nitrobenzenesulfenyl bromide with acetone, but gave no experimental details or 44 yields. Rheinboldt and Perrier have reported that the corresponding diselenides are also reduced (to diselenldes) in the presence of acetone. II. DISCUSSION When rate studies were attempted in the present study on the system II and acetone, using concentrations and conditions similar to those used in the study of the reaction of I and acetone (see Chapter III), precipitation of crystalline bis-(2,4-dinitrophenyl) disulfide, as re- r " ---- - 204 ' 56 ' ■ ;ported by Strashun, was observed. The rate curves ob- 1 tained were of the type shown in Pig. 15- On completion ! of this run (see Table XCV), fifty hours after mixing, the i < , ' 1 •'precipitate was collected, dried and weighed. It proved 1 to be 0.0023 moles of bis-(2,4-dinitrophenyl) disulfide. i 1 » * i ’ Titration of the solution at this time required 0.0046 ; iequivalents of thiosulfate. Since only 0.0068 equivalents t of II were used, and 0.0046 moles are needed to form the ' 1 i disulfide obtained, at most only 0.0022 moles of the i ! 1 | sulfenyl bromide could have been present at the time of the 1 titration. Thus it was apparent that some reaction(s) must j ; i ; have occurred which produced the disulfide and simultaneous-i > . 1 i ly produced some substance capable of reacting with iodide 1 ! 1 ! ion to release iodine under the conditions of the titra- 1 1 i j tion. For this reason it seemed desirable to repeat , I l Strashun's synthetic work, using conditions similar to . those used in these rate studies. I 1 j j When this was done, the results were very similar to j ■ ' those of Strashun. Both the disulfide and the acetonyl I i : sulfide were found, with the disulfide predominating. The I presence of bromoacetone was proved by converting it to a ; ! thiazole derivative by reaction with phenylthiourea. The 1 crude bis-(2,4-dinitrophenyl) disulfide, as obtained from ' this reaction mixture, was shown to be incapable of releas-{ 1 ! j ing iodine in the titration. __________________________ _ J 205 It appears that the ehief reaction which occurs is (I), below (Ar = 2,4-dinitrophenyl)> while a concurrent but apparently slower reaction is (2). It was also shown that the reaction of acetophenone with II leads to the simultaneous production of both the disulfide and the phenacyl sulfide. + 2 ArSBr = CH^OCHgBr + ArSSAr +■ HBr (2) CH3COCH3 + ArSBr = ArSCH2COCH3 + HBr Since neither the disulfide nor the acetony;! sulfide, formed above, releases iodine from Iodide ion, it must be the bromoacetone which does so. To confirm this conclu- 7 sion, authentic bromoacetone was titrated by a procedure identical to that used in the rate studies. The results are given in Table XCVTII. It seems likely that the re action which occurs is as shown below. This is analogous to the reaction observed by Newman between phenacyl bromide and aqueous hydrobromic acid. (3) CH^COCHgBr + 2 I" + H+ = CH3COCH3 +’ Ig + Br" This equation predicts the release of two equival ents of iodine per mole of bromoacetone; the results of the titration approach this amount. The deviation from the expected stoichiometric quantity (two equivalents) of iodine may be explained by the probable reaction of bromo- ; acetone with acetic acid (used in the titration mixture) ) and also possible by spontaneous decomposition of the I ' j bromoacetone in the interval (about three hours) between ; its preparation and titration. (Brendler reports that j bromoacetone decomposes spontaneously even when pure.) | The leveling-off effect in the rate curves (see ; Fig. 15) thus appears to be caused by the formation of 1 ' bromoacetone via equation 1. This product releases ; iodine, via equation 3> and thus replaces II in the role ! of releasing iodine, equivalent for equivalent, in the t 1 ' titrations. The rapid decrease in equivalents of iodine 1 l found at the beginning of each run may be partially ex- \ j plained by the fact that the bromoacetone is not fully j equivalent to II in its ability to release iodine (as j shown in Table XCVIIl). Some of the sulfenyl bromide is j also being used up in a reaction (equation 2) in which.no 1 substance capable of liberating iodine from iodide is pro duced; and it would be expected that the iodine titer should drop to the extent to which this reaction occurs. 1 j The drop in iodine titer observed probably results from a ' combination of these causes, each one being of about equal 1 importance. ! Because of the complexities and inaccuracies in- 1 1 ; herent in the titration method as applied to this system, Lit. was_appar_ent_th.at_the_rate„data_obtained_cpuld_only__be_ r . . . . . . . . . . . . . . . . . _ - .. — 2 0 7 ‘ ; : i considered as useful for qualitative discussion. However, other data on the effects of illumination and possible j S catalysis was sought. Parallel runs in transparent and j i i black flasks indicated that there was little or no effect ' i t | ; caused by ordinary illumination, and a run with added ; ; i ! hydrogen chloride indicated that there was no significant j i * 1 acid catalysis. | I A product run, using methyl acetate as solvent, was | : also made. It was found that the products and their rela- j * tive amounts were similar to those obtained in ethylene j ; chloride as solvent. I 1 Since the reaction of II with acetone proceeds to j apparent completion in less than three hours, it is ob- j j viously much faster than the corresponding reaction of I ! ; ' t ■ with acetone, which, under the same conditions, has a half-i ! ‘ j : life of about twenty-four hours. This rate difference, as j i . 1 j well as the distinctly different nature of the products ! j from that of the corresponding sulfenyl chloride (and j thiocyanate — see Chapter Vi) suggests the possibility j ; that the reaction with the bromide proceeds by a different I type of mechanism. One free radical reaction scheme which j : I I seems to lead to the observed products in a reasonable \ ! manner is outlined below. j i Step 1. ArSBr = ArS* + Br- 1 208 Step 2. ArS • 4 CH^COCHg = ArSH 4- CI^COCHg* 2a ArS* + ArSBr = ArSSAr 4 Br* 2b ArS* + ArS* = ArSSAr 2c Br* 4 CH^COC^ = HBr 4 CR^COCHg* 2d Br* + ArSBr 4 Br2 ■+ ArS* 2e CH3COCH2* + ArSBr = CH^OCHgSAr 4 Br* 2f CH3COCH2- 4 ArSBr = CH^COCHgBr 4 ArS* 2g Further reactions which may be occurring simultaneously are: 3- ArSH 4 ArSBr = ArSSAr 4 HBr 4. Br2 4 CH3COCH3 = CH^COCHgBr 4 HBr 5- ArSH 4 Br2 = ArSBr 4 HBr 6. ArSH 4 CH3C0CH2Br = C^COCHgSAr 4 HBr In addition to the reactions above, are all the possible reactions involving combination of two of the radicals. Reactions 2b and 2e constitute a chain mechanism for decomposition of the sulfenyl bromide into disulfide and bromine; a decomposition which does not occur if II is exposed to the conditions of the reaction, but acetone is not added. Therefore, it seems that this chain, plus re action 4, is not important in the reaction. Bond energy 41 data indicate that reaction 2e might be expected to be particularly unfavorable, which may explain the stability , of the sulfenyl bromide in solution. ; i > 1 Reactions 2a plus 2g and reactions 2d plus 2f con- j i stitute chains which could account for the formation of I ; i ! all the observed products and the high rate of the reaction; | It is interesting to note that these mechanisms also ac- ! ; ■ ! i count for the formation of some acetonyl sulfide, making * j it unnecessary to postulate a second, simultaneous ionic ! reaction to account for this product. Nevertheless, 1 i I several objections can be raised to these possible paths < j _ j I for the reaction. Reaction 2a is particularly unlikely, > i x i ! for it requires a relatively stable radical, ArS* (see j * 1 1 I I discussion below) to remove a hydrogen atom from the carbon! ' O HR ! alpha to a keto group — whereas such hydrogens are known j ; to be particularly resistant to removal by free radicals. i j A-similar, though less serious objection can be made to reaction 2d. One would also expect that reaction 2g would : predominate over 2f, even to the exclusion of the latter, i | since the resonance-stabilized ArS* radical produced,in 2g | should require far less energy for its formation than the i bromine atom of 2f. This resonance consideration is the j | dominant factor, since the bond being broken is the same in I ! both cases, and the bonds being formed, C-Br and C-S are ! of approximately equal energy. Therefore, it is very I likely, if the reaction proceeds by one of these chain „paths.,_that„chain_2a_plus_2g„is_the_major_one;_and_that ! 210 most of the acetonyl sulfide is produced by reaction 4. ' It should be recalled, however, that reaction 2a is probably unfavorable. Another possible chain through which the reaction may occur is 2b plus 2d plus 2g. However, reaction 2b is unlikely (as an important step) since it involves the reaction of'a comparatively stable radical to produce a "hot" one. Evidence against the chain reactions mentioned above is found in the following: (l) No oxygen effect was observed. When experiments were performed which were identical in all respects, except that in one oxygen was rigorously excluded, and in the other oxygen was deliber ately added, no significant difference in product or time required for the reaction xvas observed. If the reaction proceeded by a chain mechanism, as described above, oxygen should break the chains by reacting with the chain carrier, CH^COCHg*, and possibly with ArS*; (2) sunlight appeared to change the nature of the reaction rather than to ' catalyze it; (3) diphenylmethane -- which would be expected to be a very effective "trap" for bromine and acetonyl 1 ' radicals — neither inhibited nor changed the nature of the reaction. , It is, however, possible to accoxont for the major . -products..by a_non.-chain _radical„mechanism,_such-_as_ - v.- - ; a reaction sequence involving 1, 2d, 2g and 2c. Both re- j actions 2d and 2g would be expected to be favored on the i ' basis of bond energies and resonance stabilization of the ! i ! product radicals. However, reaction 2c, which is essen tial in this path -- and which could be important as a 1 chain-breaking reaction in a chain mechanism path -- re- J j quires careful consideration to justify its use. Normally, j the formation of a major product, by collision of two free i I » t : radicals may be excluded as a possibility because of the j : I , very low concentrations of the radicals (a result of their j ; high reactivity). This makes improbable a collision between t i ' two of the radicals, as compared to the probability of j * • ! , collision -.with a normal molecule in the solution. However, i ; there are certain organic free radicals, e.g. trlphenyl- | methyl, which are relatively stable in solution and are i j icomparatively non-reactive, and these may accumulate in j ! | I the solution to the point where their second order combina- ■ : tion becomes important. That the ArS* radical might be jexpected to be of this type was indicated by the work of ; 47 48 4q iSchonberg ^ and co-workers, who showed that when |phenyl disulfide is dissolved "in indifferent media" at . j I elevated temperatures, behavior analogous to that of hexa- ! i ■ 1 iphenylethane is observed. This behavior was attributed ; to the presence of radicals of the type CgH^S*, and it was I shown that even, under mild_jtemperatur.e_conditions_solutions_ 212 of phenyl disulfide displayed reactions to be expected of CgH^S* radicals. Such radicals would presumably be stabilized by the possibility of resonance, some of the If such is the case, it would appear that the 2,4-dinitro- phenylthiyl radical should also be quite stable. In fact, the resonance theory predicts that it would be even more stable than the phenylthiyl radical, because of the ability of the nitro groups to participate in the resonance: That substitution of nitro groups in the aromatic nucleus can stabilize the radicals is shown by the work of Allen Quite convincing evidence against the abofe, or any other non-chain radical mechanism is the observation, men tioned previously, that diphenylmethane does not interfere with the reaction. In any non-chain radical formulation for the reaction, the first step must be Step 1, and one major contributing forms being shown below. (2 forms) N0P (2 forms) and Sugden1 on tri-p-nitrophenylraethyl. mole of ArSBr must dissociate for every mole of product formed. The bromine atoms thus produced must then react with other molecules present In the solution. Since di- phenylmethane, when present, is by far the most reactive species towards bromine atoms, virtually all of the latter should therefore disappear through reaction 5, and forma tion of bromoacetone would thus be prevented. j ! 5. Br- + (C6H5)2CH2 = HBr + (CgH^CH* Also, if the sulfenyl bromide can dissociate suf ficiently rapidly to permit a non-chain radical reaction at the rate observed, it should react with diphenyl- methane alone to give benzhydryl bromide and some product of the 2,4-dinitrophenylthiyl radical, probably the di sulfide. However, when the sulfenyl bromide and diphenyl- methane were mixed under the conditions used for the sulfenyl bromide-acetone reaction, no reaction was observed. Thus, the evidence seems to rule out, or at least makes very unlikely, either a chain or non-chain radical mechanism. There is, however, a possibility that a radical mechanism such as: 1. ArSBr --> ArS* + Br* 3. BrCH0CCH~ + ArSBr --> BrCHL£BrCH~ + ArS • ^OH 5 OH \ 5 ^BrCHgCOCH-- +~ HBr. 214 4. ArS* + ArSBr --> ArSSAr + Br* occurs, and that Step 2 is faster than the reaction of bromine atoms with diphenylmethane. That Step 2 might be fast is supported by the fact that, in the non-Markowriikoff addition of hydrogen bromide to propylene, the "radical trap" propylene is apparently unable to prevent the rapid addition of bromine atoms to the olefinic linkage. Another possible explanation for the formation of the disulfide and bromoacetone is suggested by the work of S2 Pries and Shurmann^ who implied that certain sulfenyl bromides react with hydrogen bromide in hot acetic acid to form disulfides. However, when II and hydrogen bromide were mixed under the conditions for the reaction of acetone and II no disulfide was formed, the result being the same whether or not oxygen was present. The latter test was made, since oxygen could conceivably have catalyzed the reaction by producing bromine' atoms from hydrogen bromide. There is also an ionic mechanism which can be writ ten to account for the products observed in the sulfenyl bromide-acetone reaction: -L H • • Step 1: CH^COCH^ ^--- > CH2=C(OH)CH3 Step 2: ArSBr • +•/ CH^CCOH)^ = BrCH2COCH3 + ArSH Step 3: ArSH + ArSBr = ArSSAr 4 HBr 3a 215 ArSH + CH^COCHgBr = CH^COCHgSAr + HBr 3b This mechanism would predict acid catalysis — an effect which was not observed. However, the reaction pro duces hydrogen bromide,.and a short induction period may easily have been overlooked. In connection with this, the experiment described in Chapter IV involving the bromination of acetone in methyl acetate, as well as the work of Cath ie cart indicate that the induction period is only a few minutes or less in length. To account for the observed ratio of products (see above), it is necessary that the presumed reaction 3a be considerably faster than 3b. That this is so has been confirmed by an experiment in which sulfenyl bromide and acetonyl bromide were allowed to com pete for a limited amount of 2,4-dinitrothiophenol. The disulfide was formed in almost theoretical yield — and only traces of acetonyl sulfide were found. That any sig nificant amount of acetonyl sulfide is found at all in the reaction with acetone may well be due to the fact that towards the end of the reaction the concentration of sulfenyl bromide is very low, while that of bromoacetone is high -- thereby facilitating reaction 3b. The supposition that a direct reaction of the sulfenyl bromide with acetone leads to both sets of pro ducts (i.e. Br-CH2COCH3 + ArSSAr; and ArSCHgCOCH^ + HBr) does not seem feasible, for it would require that the sulfenyl bromide be capable of reacting simultaneously in -4- — two distinct ways — one involving ArS Br and the other involving the reverse polarization. Such a situation seems unlikely. Ill. EXPERIMENTAL 1. Preparation of Reagents. a. 2,4-Dinitrobenzene- sulfenyl bromide (II) was prepared as described in Chapter II. Attempts to develop a synthesis of this substance (corresponding to the method of. Kharasch, Gleason and O " 1 Buess^ ), directly from bis-(2,4-rdinitrophenyl) disulfide and bromine .were made. A typical reaction for this purpose was as follows: The disulfide was placed in a 500 ml. 3-neck flask fitted with a mechanical stirrer and a drop ping funnel (or tube) and mixed with 200 ml. of dry ethylene chloride. The catalyst was then added in one portion and a solution of bromine in ethylene chloride ^ dropped in.: slowly, with continuous stirring. After the addition was complete, the mixture was stirred about an hour longer, then about 5 ml. absolute ethanol was added (to destroy the catalyst), followed immediately by 100 to 150 ml. of 6 N hydrochloric acid. The layers,were mixed, the unreacted disulfide (which is insoluble in both layers) collected, and the organic layer o_f the filtrate 21? separated and dried over magnesium sulfate. The solvent was removed (steam and aspirator) and the resulting brown oil treated with 1Skellysolve' B containing a small amount of benzene. The crude product, thus obtained, was then recrystallized from dry carbon tetrachloride. Table XCIV summarizes the experiments carried out in this manner. In every case the crude product was a brown amorphous solid, far inferior in quality and quantity to the product obtainable by the exchange reaction of the sulfenyl chloride with aluminum bromide. It is evident that the cleavage of the disulfide by bromine to form the sulfenyl bromide occurs neither as • readily nor as free from side reactions as the eorrespond- 31 ing cleavage by chlorine under similar conditions. This is probably due to the weakness of bromine as an oxidizing agent as compared to chlorine (the conversion of disulfide to sulfenyl halide requires the oxidation of sulfur by one electron. : One attempt to cleave the disulfide with bromine in pyridine solution was made. This solvent was chosen be cause it is a particularly good one for the difficultjly- - soluble disulfide. A reaction mixture of 2.28 g. disulfide, 1.0 ml. bromine, and 80 ml. pyridine was heated on the steam bath with occasional swirling for two hours, poured into ice, 100 ml. ethylene chloride added., .and the.mixture 218 • TABLE XCIV SYNTHESIS OF 2,4-DINITROBENZENESULFENYL BROMIDE I Wt. ArSSAr Cat. gr. Br2 Time for Add. (hr.) Temp. °C * Crude Yield . S*. ArSSAr Recov. 1 ** 1. 10.18 5 dr. fuming h2so4 5.6 1 -R.T. 3 0.0 i i 2. 8.23 4.45 g. aici3 3.74 1 -6 2 4.1 36 3. 10.24 2.12 g. AlBr^ 4.68 20 0 0 0.3 8.89 14 4. 9.94 12.8 g. AlBr^ 4.36 0.5 R.T. 3 5.5 3.54 61 5. 9.82 12.8 g. AlBr,3 4.99 3.5 R.T. 0 .10.6 y t y J f c j f c s | c 6. 9.42 13.6 g. AlBr^ 4.36 0.5 0 20 8.0 60 7. 9.00 12.9 g. AlBr^ 4.68 3 0 20 8.! 0.52 68 8. 10.80 11.2 g. AlBr3 3.90 10 0 15 7.0 3.82 71 ; 9. 9.35 10.0 g. AlBr3 4.36 3 0 5 5.2 3.54 64 Time after addition in hours. ** Crude yield ($) based on disulfide not recovered. *** The crude product was very impure as indicated "by its melting point — 94-96°. When recrystallized (with de- col orization) from carbon tetrachloride only 4.88 g. of ArSBr (corresponding to 35$ yield from disulfide) m. p. 102.5-104.5° were obtained. 219 TABLE XCIY (CONTINUED) SYNTHESIS OB 2,4-DINITROBENZENESULEENYL BROMIDE _ Time Wt. gr. for Temp. Crude ArSSAr . . . ArSSAr Cat. \ Br0 Add. °C Yield Recov. __________! ______ ________(hr.)___________ g.__________ Note: In all cases the crude product melted between 90 and 100° and product melting above 100° could only be obtained in 50 to 10% yield by recrystallization of this material. 220 worked up as before, except that no ethanol or HC1 was added. About half (1.2 g.) of the disulfide was re covered, and no II could be detected; only a small amount of tarry material was found in the ethylene chloride solu tion. b. Bromoacetone. Bromoacetone was prepared as 7 described in Organic Syntheses♦ c_. Phenylthiourea. This substance was prepared i by allowing phenylisothiocyanate to react with excess con centrated ammonia solution at room temperature for twenty hours. After recrystallization from ethanol the product melted at 152-3°. d. N-(4-methyl-2-thiazolyl) aniline. This com pound was prepared according to the method of Hurd and 27 Kharasch except that bromoacetone was used in place of chloroacetone. The product was a pale yellowish-green crystalline solid, m.p. 115-7°• _e. Diphenylmethane. Commercially obtained ma terial was purified by fractional crystallization. f_ . Cyclohexene. Material previously distilled from Zn dust and stored over sodium wire was used. g. Oxygen-free nitrogen. Nitrogen gas (Linde Aii? Products) was passed through a tower containing Fieser's 20 solution and then through sulfuric acid. h. All other materials used were prepared as. 221 previously described. 2• Attempted Rate Studies of the Reaction of II with Acetone, a. Run 72 was carried out as described in Chapter III paragraph 10-a except that II was used in place of I. In removing the samples for titration, care was taken not to remove any of the precipitated solid in the flasks. (See Table XCV.) b. Rim 73 was carried out as in a, above, except that the flask used was painted with heavy black asphalt paint (see Table XCVlJ. c_. Run 74 was carried out as in b, above, except thatv'the solvent was presaturated with dry hydrogen chloride gas at room temperature (see Table XCVIl). 3• Reaction of II with Acetone; Determination of Products. A solution containing 4.746 g. (0.0170 moles) II, and 25.0 ml. acetone, in 100 ml. ethylene chloride was al lowed to stand (in a glass stoppered flask) at room tem perature for four days. A considerable amount of an acidic ‘ gas, presumably hydrogen bromide, was observed when the flask was opened and while handling the solution. The precipitate present was collected, dried and weighed, and found to be 2.887 g. (0.00725 moles) of bis-(2,4-di- nitrophenyl) disulfide; yield 85.4 per cent. Since this, .compound is insoluble in acetone, whereas..the most ..probable 7222 7*0 6.0 5.0 3.0 12 Time (hrs.) FIGURE 15 223 TABLE XCV Temp.: 26.5° Run 72 Solvent: CE^ClCHgCl Time (hr.) Equiv. I2 in Titr. xlO5 Apparent ArSBr Cone. xlO^ (m/1) 1. 0 6.474 5.148 2. 0.5 5.671 4.510 3. 1.5 4.752 3.785 4. 3 4.557 3.635 5. 5.83 4.605 3.665 6. 10.58 4.533 3.605 7. 13.33 4.600 3.660 8. 29.75 4.592 3.'656 9. 32.17 4.628 3.681 H O • 50 4.663 3.715 224 TABLE XCVI Temp.: 26.5° Run 73 Solvent: CH^ClCHgCl _ . . Apparent m™. Eduiv. ArgBr ,T“ es 2 Cone. (mm.) Sound xlO^ ________________________- y c i ____________(m/1)_____ 1 .. 0 15.646 6.221 2. 6 13.78 5.472 3. 16 12.70 5.050 4. 31.5 12.32 4.905 5. 44 12.20 4.850 6. 55 12.18 4.846 V ■ 225 TABLE XCYII Temp.: 26.5° Rim 74 Solvent: CHgClCHgCl Time (min.) Eguiv. Eouild xlO5 Apparent ArSBr Cone. xlO2 (m/1) 1. 0 17*396 6.917 2. 6 17.240 6.853 3. 17 16.290 6.484 4. 26 14.839 ' 5.907 , 5. 37 14.376 5.711 6. 47 13*815 ' 5.516 7. 59 13.750 5.468 8. 76 13.’ 611 5.424 ■9... . 1 . 4 . 6 13.258 5.270 impurities were acetone soluble, it was refluxed with acetone to purify it, collected, dried and analyzed. Analysis: Calculated for C^HgN^O^Sg: C, 36.18; H, 1.52; Found: C, 36.06; H, 1.8l. The .highly lachrymatory solution was concentrated by distillation to about one-third of its original volume, '1.3 g. of phenylthiourea added, the solution refluxed about thirty minutes, cooled, and extracted with ca. 3 N hydro chloric acid. The combined extracts were poured into excess cold ammonia solution and the resulting tan solid separated and recrystallized from ethanol-water mixture. A pale-tan crystalline product m.p. 115-H7°> and giving a mixed m.p. of 115-117° with authentic N-(4$?methyl-2-thiazolyl) aniline was obtained. § c iM - i!! CH^COCHgBr + CgH^NHCNHg = gjC C-NHCgHg + HBr 4 - HgO The organic layer left after the acid extraction was concentrated (aspirator-steam bath) to a dark-brown viscous oil. This was taken up in hot absolute ethanol, decolorized with charcoal and chilled, yielding lustrous orange-brown crystals, m.p. 139.5-140.5°, corresponding to 2,4-dinitro- phenyl acetonyl sulfide. Titration of Bromoacetone. A small sealed weigh ing bulb containing 0.3955 g. freshly prepared bromoacetone 227 'was broken under the surface of 100.0 ml. of ethylene chloride in a glass stoppered flask and solution effected. ■Aliquot samples (10.0 ml.) were removed (pipette) and titrated using the same method as for II (see Chapter II). The results are shown in Table XCVTII. 5. Reaction of II with Acetone, in Methyl Acetate. A solution of 3-76 g. (0.0135 moles) II and 3*0 ml. (0.041 moles) acetone in 100.0 ml., methyl acetate was prepared and allowed to stand at room temperature in a dark cabinet for eight days. The resulting yellow precipitate was sepa rated, washed with fresh methyl acetate, and dried (2.29 g. 0.00575 moles). It corresponded, in solubility and melting behavior, to bis-(2,4-dinitrophenyl) disulfide; yield 86 per cent. Phenylthiourea (2.31 g.) and 150 ml. ethylene chlo- ride were added to the combined filtrate and washings and the solution heated for about one hour on the steam bath, .allowing the methyl acetate to escape. The cooled solu tion was extracted with 150 ml., then 60 ml. of 3 N hydro chloric acid, and the combined extracts poured into excess , cold ammonia solution, producing a white solid, m.p. 110-12°, . corresponding to impure N-(4-methyl-2-thiazolyl) aniline. The remaining organic layer was concentrated to a brown oil, which, when crystallized from absolute ethanol, with de- 228 TABLE XCYIII IODIMETRIC DETERMINATION OF BROMOACETONE Moles CH3COCH2Br Used Equiv. 12 Round . f o CH,C0CH2Br (based on •fcwo equiv. per , mole) • !• 0.0002987 0.000488 84.5' 2. 0.0002987 0.000512 88.6 3. 0.0002987 0.000504 87.2 Average 86.8 229 : colorization, yielded 0*65 g. of yellow solid, m.p. 126-136 (corresponding to 0.00253 moles -- yield 18 per cent— of 2,4-dinitrophenyl acetonyl sulfide). 6. Effect of Oxygen on Reaction of II and Acetone, a. Ethylene chloride (100 ml.) and acetone (25.0 ml.) were mixed in a 300 ml. glass stoppered black flask and heated (the mouth of the flask being protected by an extension , tube, closed with a calcium chloride drying tube, until the refluxing solvent vapors completely filled the flask. It was allowed to cool under a stream of dry nitrogen, and , then 2,480 g. (O.OO889 moles) of II added and the flask set aside at room temperature for forty-eight hours. The disulfide and acetonyl sulfide were isolated as described : previously. Yields: bis-(2,4-dinitrophenyl) disulfide, ; 1.392 g., 79*5 cent; 2,4-dinitrophenyl acetonyl : sulfide, 0.421 g., 18.5 per cent. b. Ethylene chloride (100 ml.) and acetone (25.0 ml.) were mixed in a 300 ml. glass stoppered black flask and oxygen bubbled through for five minutes. II (2.9185 g. -- 0.0104 moles) was added and the flask set aside at room temperature for forty-eight hours and then analyzed as described above. The yields were 1.731 g* of bis-(2,4-di nitrophenyl) disulfide (83*5 per cent); and 0.456 g. of 2,4-dinitrophenyl acetonyl sulfide (17.1 per cent). 230 7« Reaction of II with Acetone In Sunlight♦ A solu tion containing 2.0 ml. (0.0274 moles) acetone and 3*201 g. (0.0115 moles) II in 100 ml. ethylene chloride was prepared, in a pyrex glass stoppered flask, suspended in a beaker of distilled water, and set in bright sunshine for seven hours. After this period the solution had turned into an opaque, red-brown mixture. This was allowed to stand at room tern- , perature in a dark cabinet for twenty-eight hours, the brown precipitate was separated and washed with ethylene chloride. The weight was 0.516 g., and the product darkened but did not melt at 250-300°. The product is possibly a polymer of 2,4-dinitrophenylthiyl radical for it does not correspond in physical characteristics to bis- (2,4-dinitrophenyl) disulfide. When the filtrate was treated with phenylthiourea, 1 as described previously, considerable amounts of an orange precipitate were noted, although in previous cases a clear t yellow solution was obtained at this point. The orange solid was separated. It was insoluble in dilute hydro chloric acid, weighed 0.7933 g** and blackened, without melting at 200-300°. Attempted isolation of N-(4-methyl-2- thiazolyl) aniline, in the usual manner, produced only a red oil from which no solid material could be isolated. Attempted separation of acetonyl sulfide gave a small amount of a brown tar, from which.no. definite product, was _ isolated. The products of the reaction were not investi gated further. 8. Reactions in the Presence of Diphenylmethane. k solution of 4.671 g. (O.OI67 moles) II and 8.16 g. (0.0486 moles) diphenylmethane, in 200.0 ml. ethylene chloride, was ! prepared and immediately divided into two equal portions (by pipette) and 5.0 ml. of acetone (0.0675 moles) were added to one (solution A). The other, solution B, was retained as control. Both were allowed to stand undisturbed \ in a dark cabinet for seven days. Solution A: A precipitate v^as observed in the solu tion within three hours after mixing. After the seven days had elapsed, the flask was opened (acid fumes were observed) and the precipitate collected and washed with fresh ethylene chloride. It proved, by melting and solu bility behavior, to be 1.28 g. (0.00322 moles -- 77 cent yield) of bis-(2,4-dinitrophenyl) disulfide. The ethylene chloride solution was treated as described pre viously (see above) to prove the presence of bromoacetone and to isolate the acetonyl sulfide, of which 0.4l g. (0.0016 moles -- 19 per cent yield) m.p. 134-5° was found. Solution B: After the seven days had elapsed the solution was still clear and gave a positive test with iodide-starch solution. Cyclohexene (5.0 ml. -- 0.0495 232 moles) was added. After two hours, the still clear solu tion gave a negative test for sulfenyl halide. It was then concentrated to about 5 ml. (steam bath aspirator) and an equal volume of absolute ethanol added. The resulting yellow crystals (wt. 3-01 g., m.p. 105-7°) were recrystal lized from absolute ethanol yielding 1.77 g. 2,4-dinitro- phenyl 2-bromocyclohexyl sulfide, m.p. 117-118° (crude yield-, 0.00834 moles — 100 per cent; purified product, 0.00490 moles — 59 per cent). 9* Possible Reaction of II with Hydrogen Bromide. About 500 ml. ethylene chloride was shaken with.several portions of ferrous ammonium sulfate solution until no more ferric ions were produced, as shown by testing with potassium thiocyanate. It was dried over calcium chloride and then over "Drierite"; boiled at reduced pressure for a few minutes and oxygen-free nitrogen bubbled through for fifty minutes. It was then saturated with hydrogen bromide gas (previously dried through calcium chloride and sulfuric acid) and divided into two approximately equal portions in glass stoppered flasks. Oxygen was bubbled through one for three minutes, and then 3.0 g. of II was added to each and the flasks set in'a-dark-cabinet at room temperature. Even after two days,, no trace of disulfide formation was noted in either flask. Acetone (3.0 ml.) which had been 233 swept with nitrogen was then.added to each flask, and within several hours disulfide formation was noted in both cases. Working up of the reaction mixture, as previously ! described, showed that the disulfide and acetonyl sulfide were formed in both cases in approximately the same ratio as had been previously observed. ■ Competitive Reaction of II and Bromoacetone with .2,4-Dinltrothiophenol. A solution of bromoacetone was pre pared by dissolving 3*0 ml. (0.04l moles) of acetone in 200 ml. methyl acetate and adding 2.2 ml. (0.041 moles) of bromine. The solution became colorless within one minute, ! indicating complete reaction. To 100 ml. of this solution in a glass stoppered flask was added 3*7 g. (0.0133 moles) •of II; then 2.8 g. (0.0140 moles) of 2,4-dinitrothiophenol was added, solution was effected by vigorous mixing, and the flask set in a dark cabinet at room temperature. i Formation of a precipitate was noted almost immediately : i after mixing. After four days, the precipitate was col- 1 .lected, washed thoroughly with warm methyl acetate and ' dried in an oven at 60° for several hours. It corresponded .in>solubility and melting behavior to bis-(2,4-dinitrophenyl) I disulfide; 5.56 g-j 105 P®*? cent. | * The yield calculated is based on II present. To ac count for the high yield it must be assumed that some of the- :thiophenol_was ^oxidized.by impuri.ties_to .the..disulfide_._i 234 Evaporation on the aspirator of the methyl acetate from the combined filtrate and washings yielded only a very small amount of brown oil from which a minute amount Of yellow solid., m.p. 125-130°, mixed m.p. with authentic acetonyl sulfide 130-135°, could be isolated. CHAPTER VI RELATED STUDIES A number of related studies were carried out in con junction with the work already described. The studies of the reaction of 2,4-dinitrobenzenesulfenyl thiocyanate with acetone and of I with acetoacetic ester were carried out to shed further light on the reactions described in Chapters III, IV, and V. The study of the reaction of I with acetone in different solvents was undertaken because of the need to find a solvent for a kinetic study of this reaction (other than those whose use is described in Chapter III). The study of the solubility of salts in methyl acetate became necessary when it was found that commonly used salts were not soluble in this solvent. The other two studies described — the decomposition of I in sunlight and the competitive reaction study -- were made chiefly as the beginnings of other studies planned; a study of the free radical reactions of sulfenyl halides, and a study of the comparative basicities of organic compounds toward I, respectively. I. THE REACTION OF 2,4-DINITROBENZENESUIFENYL THIOCYANATE WITH ACETONE Introduction. Kharasch, Wehrmeister and Tigerman-^ 236 have reported that 2,4-dinitrobenzenesulfenyl thiocyanate (ill) reacts with acetone to give, as does, the sulfenyl chloride, 2,4-dinitrophenyl acetonyl sulfide, and, pre sumably, thiocyanic acid (HSCN). An exploratory study of this reaction was undertaken for the purpose of compar ing (and relating) this reaction with those of the sulfenyl chloride and bromide discussed previously. Discussion. When preliminary rate studies were at tempted for this reaction, under conditions and concentra tions similar to those for the sulfenyl chloride-acetone reaction described in Chapter III, it was found that about fifty hours were required for 10 per cent of the sulfenyl thiocyanate present to react, using ethylene chloride as solvent. When the concentration of acetone was increased from one-fifth to two-fifths of the solution (by volume -- tcorresponding to a change in molarity of acetone of 2.7 to 5.4) the rate increased greatly, and it was found that the results appeared to fit first order kinetics, similarly to the sulfenyl chloride-acetone runs. That the product of the reaction is indeed the acetonyl sulfide was shown by isolation of this material from several of these completed runs. More accurate rate runs were then carried out in the same black flasks and constant-temperature bath as were 237 ■used for runs eight through eleven (see Chapter III). Run 75 (see Table XCIX and Pig. 16) was made using a solvent' mixture which was one-fifth acetone (approximately 2.7 molar) and in Run 76 (see Table C and Pig. 17) the solvent was one-fourth acetone (approximately 3.4 molar). In both of these runs it was found that the rate constant (as calculated from the initial point) began to increase, at what appears to be a constantly increasing rate, after about one hundred forty hours. At about the same time that this apparent increase in rate began to oc cur, the presence of an orange precipitate in the solution was noted. On completion of the runs this substance was separated. It was neither the acetonyl sulfide nor the disulfide, and was not investigated further. The first order rate constant calculated from the data of Run 75 (up to one hundred fifty hours) is about five hundredths that of the comparable constant for the I- acetone reaction, confirming the observation that III re acts much more slowly with acetone than does I. The. anomalous increase in rate of disappearance of III, coupled with the formation of insoluble material, may be explained by the possibility of acid-catalyzed copolymerization of III with thiocyanic acid, or some other complex condensa tion. Thus the sulfenyl thiocyanate underwent two simul taneous reactions, one with acetone to form the acetonyl 238 sulfide, and the other an unknown reaction to form the orange solid. If this is so, the observed rate constant for the rate of disappearance of III actually represents the sum of the rates of the two reactions. However, if the reaction to form the orange solid is HSCN catalyzed (or re quires HSCN, as is strongly indicated by the nature of the rate curves and by the known properties of thiocyanates^) the initial slope of the plot for the III-acetone reaction should be a measure of the rate of the normal (acetonyl sulfide-forming) reaction, and thus the rate constants given (for the first 150 hours) would actually be for the normal reaction. The reaction was also carried out in methyl acetate to determine whether or not kinetic studies "under conditions similar to those used for the reaction of I with acetone in this solvent (see Chapter IV) would be feasible. Under these conditions it was found that only a very small amount (less than 5 per cent) of the "normal" product, the acetonyl sulfide, was found — the remainder of the product being an insoluble compound similar in appearance and pro perties to the orange solid obtained in ethylene chloride. This solid material was washed and submitted for analysis. Anal.: C, 33-59; H, 1.86, S, 22.34. Polymeric III would require C, 32.67 and S, 24.92; and polymeric HSCN, C, 20,32 and S, 54.26. Thus, it is apparent_that the. productJ 239 is neither of these, nor a mixture of them, nor a copolymer of III and HSCN. The analysis (high in carbon and low in sulfur) indicates that some acetone had been incorporated. 18 By analogy to the results of Fialkov and Kleiner the compound 2-hydroxy 3-(2,4-dinitrophenylthio) propyl thio cyanate (ArSCHgCH^HjCHgNCS) may be formed from the acetonyl sulfide and HSCN; and the presence of this, or a polymer thereof, in the insoluble material may be the cause of the high carbon and low sulfur content. Some polymeric form of HSCN is also probably present, as this substance 37 is known 1 to polymerize, under similar conditions, to insoluble products. E:xperlmental. 1. Preparation of Reagents. All reagents used were prepared as previously described. 2. Preliminary Rate Studies. These were carried out as described in Chapter III, paragraph 7, except that III was used in place of I, and one of the runs utilized 50 ml. acetone with 75 ml. ethylene chloride. After sufficient time for complete reaction (as indicated by a negative test for sulfenyl halide) the solution in one of these runs was filtered, the solvent removed by aspiration, and the resulting yellow solid recrystallized from absolute ethanol and shown, by melting and mixed melting point be- 240 havior, to be 2,4-dinitrophenyl acetonyl sulfide. 3. Regular Rate Studies. a. Run 75 was carried out exactly as described in paragraph 10-a, Chapter III, except that III was used in place of I. The orange precipitate was first noticed when the twelfth point was taken. Since the flask was painted black it was impossible to note the exact time the precipitate appeared. Its presence was noted by the appearance of suspended particles in the aliquots being removed for titration. At the end of the run, it was collected, washed with a small amount of ethylene chloride, and air dried. The product darkened but did not melt at temperatures near 200°, and when treated with • sodium iodide in acetic acid it did not release iodine. Re moval of solvent from the above combined filtrate and wash ings gave, after recrystallization from ethanol, a yellow solid, m.p. 139-140°. Id . Run j6 was carried out exactly as described for Run 75 except that the solution contained 50.0 ml. acetone and 150 ml. ethylene chloride. The concentration . of acetone was therefore 3.39 M. The orange precipitate ; was first noted at point 8. It was not isolated from this run. c_. A solution of .III in ethylene chloride (about 1 | 0.08 M) was prepared and set aside in a glass-stoppered ..flask, After three.weeks, no_precipitation^was ^observed... _ 241 TABLE XCIX Temp.: 26.5° Bun 75 Solvent: CHgClCHgCl Time . (hr.) Cone. ArSSCN xlO2 (m/L) Log. ArSSCF Cone. +2 kl xlO^-, hr. 1. 0 5.970 .77599 -- 2. 3 6.014 .77913 -- 3. 11.5 5.791 .76278 2.65 4. 29.33 5.651 .75212 1.87 5. 48.33 5.567 .74560 1.45 6. 52 5.350 .72838 2.11 7. 59.5 5.362 .73095 1.74 8. 72 5.313 .72536 1.62 9. 78 5.289 .72337 1.55 10. 97 5.084 .70620 1.’ 66 11. 121.5 4.942 .69387 1.56 12. 145.5 4.606 .66336 1.78 13. 171.5 4.132 .61616 2.15 14. 195.5 3.723 .57088 2.42 15. 218.5 3.251 .51195 2.78 16. 247.67 2.620 .41829 3.33 17. 269 2.270 .35603 3.60 0 0 . 1 —1 . 290.17 1.865 .27073 4.01 Average rate constant (points 4 through 12) 1.70 i 242 TABLE C Temp.: 26.5° Run 76 Solvent: CH2C1CH2C1 Time (hr.) Cone. ArSSCN xlO^ (m/l) Log. ArSSCF Cone. +2 H t A 1 H O • * 1. 0 4.365 .63998 --- 2. 2.5 4.086 .61130 26.42* 3. 26 3.910 .59220 4.23* 4. 40.5 3.822 .58225 3.28 5. 45.5 3.751 .57415 3.33 6. 66 3.520 .54525 3.31 7. 87.5 3.341 .52388 3.06 8. 115.5 3.074 .48775 3.04 9. 140 2.766 .44190 3.26 10. 163 2.225 .34740 4.13 11. 187.5 2.028 .30695 4.09 12. 208.5 1.626 .21120 4.74 13. 2.59.75 0.823 -.08439 6.42 * Average rate constant (points Omitted in calculating average 4 through 9) rate constant. 3.21 1.7 on 1.0 360 180 Time (hrs.) FIGURE 16 C O 1.0 5 180 • Time (hrs.) FIGURE 17 225 270 315 245 A similar solution containing anhydrous hydrogen chloride likewise gave no precipitation. Reaction in Methyl Acetate. A solution consist ing of 5*0 g. (O.OI94 moles) III, 5.0 ml. (0.07 moles) acetone, and 85 ml. methyl acetate was prepared in a glass stoppered flask and placed in the constant temperature apparatus at 50°. Within two hours considerable cloudiness was noted in the previously clear solution, and slow pre- , cipitation of a yellow-orange material was observed during . r the next few days. After four days, a negative test for III was obtained, the solution filtered through a tared, sintered glass funnel, and the orange solid thus obtained . washed with methyl acetate. It weighed 4.091 g., and on the melting point apparatus began to darken at 235° and melted with decomposition at 270-274°. The filtrate was taken to dryness on the aspirator and the resulting brown ; oil boiled with about 200 ml. absolute ethanol. All of the material dissolved except 0.08 g. of a yellow-brown , solid, m.p. 200-205°. The ethanol solution was concentrated (steam-air jet) to about 30 ml. and chilled, giving 0.24 g. of a yellow solid, m.p. 185-187° (with some signs of partial melting at 135-136°). Concentrating the mother liquor again to about 10 ml. produced 0.18 g. brange-brown crystals, m.p. 131-13^°• ' These, when recrystallized from absolute, ethanol,. gave_. _ ^ 246 excellent yellow crystals which corresponded in melting and mixed melting point behavior to 2,4-dinitrophenyl acetonyl sulfide. II. THE REACTION OF 2,4-DINITROBENZENESULFENYL CHLORIDE WITH ACETOACETIC ESTER 66 ; Introduction. Zincke and co-workers have shown > t that aromatic sulfenyl halides react with acetoacetic ester to substitute the arylthio group onto the methylene position. Because of the greater reactivity of its active ; hydrogens, it was considered that a preliminary study of : the reaction of acetoacetic ester with I, done in parallel with the acetone study, might be informative. Discussion. The product of this reaction has not been reported in the literature. Its preparation and analysis are described in Chapter II. When preliminary rate studies were carried out under conditions identical to those used for the acetone studies (see Chapter III), rate data were obtained which indicated r that the reaction was very similar to that of I and ace tone. No indication of an initial high rate, corresponding, to the high end content of acetoacetic ester, was observed. The rate of the reaction (k^ - 0.020 hr.-' * ' ) corresponded i very closely with the observed rate for acetone 247 (k^ = 0.029 hr.-1), indicating that the rate of reaction of a ketone with I is not Influenced greatly by the activity of the hydrogen being replaced. In view of the difficulties of the titrimetric method with acetoacetic ester present (see Chapter II), and the complexities found in the acetone studies (see Chapters III and IV), the study of the reaction with acetoacetic ester was not pursued further. Experimental. 1. Preparation of Reagents; Commercial acetoacetic ester was distilled and the middle, constant boiling frac- : tion taken. All other materials used were prepared as described previously. 2. Rate Studies. The reaction was carried out in ethylene chloride as solvent, at 26.5°» in the same manner as previously described (see paragraph 8-a, Chapter III). The solution used consisted of 75.0 ml. of acetoacetic ester mixed with 200 ml. of ethylene chloride, corresponding to a molarity of the ester of 2.14. The data obtained are shown in Table Cl. III. THE REACTION OF 2,4-DINITROBENZENESULFENYL CHLORIDE WITH ACETONE IN DIFFERENT SOLVENTS Introduction. In the investigation of the kinetics Temp.: 26.5° TABLE Cl Run 77 Solvent s ch2cich2ci Time (hr.) Cone. ArSCl xlO2 (m/l) Log. ArSCl Cone. +3 kl . -1 hr. 1. 0 5.07 .7050 -i.— 2. 0 4.91 .6911 --- 3. 2 4.68 .6703 .0322 4. 3.5 4.77 .6785 .0128 5. 6.5 4.38 .6415 .0200 6. 7.5 4.29 .6325 .0200 7. 9.5 4.14 .6170 .0196 8. 10.75 4.00 .6021 .0206 249 of the reaction of I with acetone (Chapter III), the order of the reaction with respect to acetone could not be deter mined in the solvents used, as a large excess of acetone was required to obtain a measurable rate, and when the initial acetone concentration was changed significantly, a large change in solvent property of the medium resulted. To determine the true order for acetone it was necessary to find conditions under which the reaction occurred at a conveniently measurable rate when only equivalent amounts of acetone were present. By choosing a suitable solvent and/or temperature it should be possible to increase the rate of the reaction sufficiently that satisfactory rate curves could be obtained using the low acetone concentra tions desired. For this reason!,: a study of the reaction in a variety of solvents was undertaken. Discussion. In carrying out these studies the maxi mum temperature employed was fifty degrees, since above this temperature difficulties due to the volatility of acetone would probably be experienced. The solvents used were . chosen on the basis of the following criteria: availabil ity; probable nonreactivity towards I and/or acetone; miscible with or heavier than water (preferred but not re quired); and polarity and/or oxygen content. It was ap parent almost from the start of this study that the reaction was faster in polar and oxygen containing solvents — as indeed could have been deduced from the large increases in rate caused by added salt or added acetone as reported in Chapter III. First order rate constants (from initial slopes) have been obtained for the reaction in a large number of solvents with which the sulfenyl halide did not react. j These rate constants (corrected for initial acetone con- ; centration in a manner indicated to be necessary in Chapter IV) are tabulated in Table CII. The solvents used appear to fall into three classes: l) nitrogen containing solvents, 2) oxygen containing solvents, and 3) solvents with neither oxygen nor nitrogen. Solvents of the first class apparently all interact in some way with I to form insoluble materials. This interaction is probably of the same type as that of pyridine and I, discussed in the pre ceding chapters. A probable exception to this is diphenyl- amine, which forms a low melting material, probably N,N- ; diphenyl-2,4-dinitrobenzenesulfenamide. f Solvents of class three all gave very slow rates, despite the fact that, in some cases at least, their di- • i electric constants are quite high. A striking illustra- ; tion of the lack of influence of the dielectric constant t of a solvent on the rate is the difference in. rates of re- ] action in methyl .acetate.and o-diehlorobenzenej—both. of___ j TABLE CII RATE OP REACTION IN VARIOUS SOLVENTS Solvent k~l % Acetone Ethylene chloride Negligible Nitrobenzene * 2 x 10-5 Dioxane 4 x lO"5 Tetrahydrofuran 2 x IQ-5 Ethylene chloride * Benzophenone (56 g./200 ml.} 2 x 10“5 Ethylene chloride + Benzophenone (107 g./l50 ml.) 5.5 x IQ”5 ^ ^ ’-Dichloroethyl ether Ethyl acetate 4 x 10~5 6 x IQ”5 Methyl acetate 1.5 x 10"2 Methyl acetate** 5 x 10~5 Ethyl fo rmat e 7 x 10“5 Ethyl f o rmat e * * 6 x 10“5 Benzene Negligible 1,2-Dimethoxyethane 1 x 10“2 Methyl benzoate 5.5 x 10“5 Chloroform Negligible o-Lichiorobenzene Very small Ethyl oxalate 5 x 10~5 Ethyl carbonate Very small 252 TABLE CII (CONTINUED RATE OE REACTION IN VARIOUS SOLVENTS . . Solvent kl ' i o Acetone Ethyl Orthoformate Very small * at 40 ° ** at 53° which have almost the same dielectric constant (7*3 and 7.5 respectively). That this lack of importance of di electric constant is not restricted to comparisons between oxygen and nonoxygen containing solvents can be shown by comparing the rate in methyl acetate (€ = 7*3) with the rate in nitrobenzene (€ - 36.l). Among the oxygen- containing solvents, the rate appears to be greatest in those solvents containing a carbonyl group but even this generalization is not fully valid, as the rate in / - dl1 ethyl carbonate is very small as compared to -dichloro- ethyl ether and 1,2-dimethoxyethane. However, if we assume the mechanism discussed in Chapter IV, then certain comments may be permissible. Thus, step one in that mechanism (ArSCl »ArS+Cl~) would be aided by a highly polar solvent, whereas step 2 (ArS+Cl** + acetone --> products) should be hindered by polar solvents and occur.best in non-polar ones -- its f* OH C* €+ / / •ArS ••~-CH0J“M,C-CILj having a Cl presumed transition state greater dispersion of charge than the starting material. Assuming the two steps to be of comparable rate, a highly polar solvent would therefore tend to cause the rate of step 2 to drop sufficiently to make it become rate deter- -mining — and- also so- slow that -the- over-all- rate-becomes 254 small. A highly non-polar solvent, on the other hand, would be favorable to step 2, but would presumably cause step 1 to be very slow, again leading to a small over-all rate. The best solvent would therefore be one of inter mediate polarity -- and this is exactly what is observed. Of the solvents tested which do not react with I, methyl acetate and 1,2-dimethoxyethane favored, the highest rates. Both of these solvents are water miscible and non reactive towards I -- both factors making them suitable, but they are both relatively unavailable (in pure state) commer cially. Because it can be prepared in pure form easily and from readily available and cheap starting materials, methyl acetate was chosen as the solvent for further study. Rate studies in this solvent are described in Chapter IV. A rate run made in 1,2-dimethoxyethane is described below (see Table CII and Fig. 18). It can be seen that the kinetics are not simple — that reaction appears to be between first and.sec ond order -- and there is no indication that any advantage would have been gained by using this solvent instead of . methyl acetate. Experimental. Preparation of Reagents. All solvents used, with the exception of those whose purification has already been discussed, were dried over magnesium sulfate and distilled, only the-constant-boiling middle fraction being-used.- : ' All other reagents were prepared as previously described. Rate Studies. In each case (unless otherwise specified below) a solution of I (about 3 g.) in 200 ml. of the solvent was prepared and divided into two equal portions. To one of these was added acetone (2.0 ml.) and both solutions, in glass stoppered flasks, were placed ; ! in the constant temperature bath at 50 . Aliquot samples i were removed and titrated in the usual manner from both , flasks for one to four days — as long as necessary to ' determine the approximate rate. . ] a. Ethylene chloride at both 40 and 50°. There was no detectable reaction in fifty hours. b. Nitromethane at 40°. About half of the sulfenyl halide had disappeared in forty hours, but a considerable « • t ; amount of a yellow crystalline precipitate, m.p. above j , . 200? was formed. c_. Nitrobenzene at 40°. About 15 per cent re action in fifty hours. j cL Dioxane at 40°. About 10 per cent reaction ; ; in fifty hours. > ‘ i e. Dimethylformamide. After.two hours the re- t action was essentially complete. The acetonyl sulfide was ■ observed as a product, but some insoluble high-melting material was also formed. The titer of the "blank run" . (I plus solvent alone _-- no acetone__added) decreased about J fifteen per cent in twenty-four hours. v JT. Dimethylformamide at 30°. The reaction was apparently complete in less than one hour. The "blank run" decreased 32 per cent in forty-eight hours. Prom this blank, pale yellow crystals were obtained, m.p. 270-275°. g. Mixture of 20 per cent (by volume) qf dimethyl- formamide in ethylene chloride. The solution with acetone • ■present and "blank" both reacted rapidly, giving the yellow high-melting solid observed previously. h. Acetonitrile. Both reaction and blank gave considerable amounts o'f a . yellow crystalline precipitate, m.p. above 250°. _i. Tetrahydrofuran (purified by distillation from ‘lithium aluminum hydride). The reaction proceeded about 20 per cent in 30 hours. ' j. Diphenylamine in ethylene chloride (5 g. 200 ml.). A red color was observed on adding the sulfenyl chloride. The reaction was over rapidly, both run and blank giving a red-brown solution containing, as a preci pitate, a pale green solid, m.p. 105-110°. k. N,N-Dimethylacetamide (prepared by the method of Mitchell and Reid^), (b.p. 169-169.5° uncorrected, dried 1 f over calcium sulfate). As the sulfenyl chloride was added, a.fine yellow precipitate, m.p. above 200° was formed. _. _ JL. Benzophenone in.. ethylene-chloride ( . 56- g — 1 200 ml.). The reaction proceeded about 20 per cent in seventy hours. When a mixture'of 106.6 g. benzophenone in 150 ml. ethylene chloride was used, the reaction proceeded , about 35 per cent during the same time interval. m. ^ ,^-Dichloroethyl ether. About 50 per cent reaction occurred in eighty-five hours. n. Ethyl acetate. The reaction proceeded about 65 per cent in forty hours. The blank decreased about 5 per cent during this time. When the experiment was repeated using ethyl acetate purified by the method of Fieser,^ the reaction proceeded 62 per cent in eighty-five hours, the blank showing no decrease. o. Methyl acetate. The reaction proceeded 72 per , cent in fifty hours. At 33°* using only 1 ml. acetone per 100 ml. solvent, the reaction proceeded 28 per cent in one hundred twenty-five hours. p. Ethyl formate. (dried over phosphoric anhydride),. Using 2 ml. of acetone per 150 ml. solvent, the reaction ; proceeded 20 per cent in twenty-five hours. At 33°» using similar concentrations, the reaction was almost equally 1 ( rapid. Benzene. No detectable reaction after twelve days. r. 1,2-Dimethoxyethane. Using-1 ml. acetone per 100 ml. solvent, the reaction_proceeded JA per „cent_.in. 258 ninety hours. With solvent dried over sodium, and 1 ml. acetone per 70 ml. solvent, only 60 per cent reaction oc curred in this time. s_. Methyl benzoate. Ten per cent reaction oc curred in. twenty-five hours. t _ . Chloroform. No significant amount of reaction was observed in twenty-four hours. u.7b-Dichlorobenzene. Using 1 ml. acetone per 100 ml. solvent, 4 per cent reaction occurred in thirty hours. The titrations for I were extremely difficult and poor in the presence of this solvent. v. Ethyl oxalate. Using 1 ml. acetone per 100 ml. solvent, 23 per cent reaction occurred in forty-eight hours. w. 1,2-Diethoxyethane. Using 1 ml. acetone per 100 ml. solvent, 64 per cent of the sulfenyl chloride dis appeared in twenty-five hours, but the blank decreased 35 per cent during this same time interval.' » x. Ethyl.carbonate. Using 1 ml. acetone per 100 i ml. solvent, 16 per cent of the sulfenyl chloride disap peared in twenty-five hours, but tphe blank decreased al most as much (13 per cent) during this same time interval. y. Ethyl orthoformate. No detectable reaction in fifty hours. 3. Rate Study in 1,2-Dimethoxyethane. Run J8 was carried out as described in paragraph 6, Chapter IV,. _ . ' 259 except that 1,2-dimethoxyethane (dried over sodium, then distilled) was used as solvent. The results are given in Table CIII and.Pig. 18. IV. MISCELLANEOUS STUDIES A* Solubility of Certain Salts in Methyl Acetate. Rate runs in the presence of added salt were planned as part of the study of the kinetics of the reaction of I and ■ acetone in methyl acetate. For this purpose an investiga tion of the solubilities in methyl acetate of various salts which would probably not react with I was. made. Unfortun ately a salt soluble enough to justify its use could not be found. Experimental. The salts used were prepared as fol- ' lows: a. Lithium chloride: the commercial material (Baker's C.P. was dried at 120° for three hours, b. Tetra-' methyl ammonium chloride: the commercial (Matheson praeti-, cal grade) material was dissolved in excess toluene-absolute ethanol mixture and the solution distilled until only water- free toluene remained. The solution was cooled,, and the salt was collected and kept over phosphoric anhydride un til used. £. Tetraphenylarsonlum chloride: Commercial material was used without further treatment, d. Trimethyl octadecylammonium chloride: Armour and Co. "Arquad 18" _was dried at 3 mm. Hg. pressure and 83°..over, phosphoric _ 260 TABLE ClII Run 78 Temp, s 50° Init. Acetone Cone.': 0.197 M Solvent: 1,2-Bimetlaoxyetliane Time Ur.) Cone. ArSCl xlO^ (m/l) Log. ArSCl Cone. +2 1 (ArSCl) 1. 0 19.525 1.29081 5.12 2. 18 12.110 1.08514 8.26 3. 18 12.140 1.08422 8.24 ' 4. 25 10.380 1.01620 9.63 5. 42 7.710 .88705 12.97 6. 42 7.770 .89042 12.87 . 7. 72 5.130 .71012 19.4-9 8. 93.25 4.070 .60959. 24.57 9. 93.25 4.090 .61172 24.45 10. 138 2.700 .43136 37.04 11. 138 2.700 .43136 37.04 12. 191.5 2.040 .30963' 49.02 13.. 191.5 . 1.970 .29447 50.76 s rH ; f t o ~ I o co CO ! U <5 1 bO<fl w __ OJ M in - = f - CD i°* I H in oo © 00 o in cu © O © VO o in o 0 O rnh- 0 o o 50 100 Time (hrs.) FIGURE 18 © l>irst Order © Second Order 200 anhydride for eight hours. e. Dodecyl trimethylammonium chloride: Commercial material was used without further purification, f. Sodium p-Toluenesulfonate: Commercial material was dried at 120° for eight hours. g. Lithium Tetraphenylboride: A sample was kindly furnished by Carl 6U Moeller, which he had prepared by the method of Wittig. h. Potassium tetraphenylboride: Prepared by mixing of aqueous solutions of potassium chloride and lithium tetra phenylboride. i_. Trimethylammonium tetraphenylboride: Same as g. ]j. Tetramethylammonium p-toluenesulfonate: An aqueous solution of tetramethylammonium chloride was shaken with excess silver oxide until the supernatent solution gave no reaction with silver nitrate solution, the mixture filtered, and the filtrate titrated with aqueous p-toluene- sulfonic acid solution to a pH of 6 (universal indicator paper). The solution in a beaker, was placed in a vacuum desiccator containing calcium chloride until most of the water was removed. The calcium chloride was then replaced by phosphoric anhydride which completed the drying. The solubility of each salt was measured as follows: Excess salt was placed in a 125 ml..erlenmeyer flask with 50 ml. of methyl acetate, the mixture was boiled for several minutes, filtered hot, and a 20.0 ml. aliquot of the hot filtrate removed and placed in a tared 125 ml. erlenmeyer flask. The solvent was removed, on the steam-bath and-the - - 263 erlenmeyer plus salt weighed. The results are given in Table CIV. B. The Decomposition of I in Sunlight. As a part of the illumination experiments described in preceding chap ters and as a possible beginning to a study of the free radical properties of sulfenyl halides, the behavior of I in sunlight was studied. It was found that I decomposed only slowly in sunlight, and that the products were not the expected disulfide and chlorine, but instead a polymeric substance and, presumably, hydrogen chloride. Experimental. a. A solution of 3.5 g. (0.015 moles) of I in 200 ml. of carbon tetrachloride was prepared in a 250 ml. vycor flask and placed in hazy sunshine for two and one-half days. The small amount of yellow-brown solid present, 0.16 g., was separated leaving a green solution. On the melting point apparatus it decomposed to a black tar at 200-250°. The filtrate was allowed to stand at room temperature for forty-eight hours, during which a consider able amount of precipitation was noted. The mixture still gave a positive iodide-starch test, so the presence of chlorine was suspected. The solution was distilled to about half the original volume, the vapors obtained being passed into cold ethylene chloride. The resulting ethylene chloride solution gave white fumes with air, and 264 TABLE CIV SOLUBILITY OP SALTS IF METHYL ACETATE + Grams bait per 20 of salt m. Soln. Solubility moles/liter 1. Li Cl* H O • 0.012 2. (ch3)4h+ci" neg. neg. 3. (ch5)3nc18h37ci“ ? ... neg. neg. 4. (c6h5)4as+ci~ .005 neg. 5. + (CH3)3FC12H25C1_ .04 0.0076 6. Na+p-CH3G6H4S03 .02 neg. 7. (ch3)4f+p-ch3c6h4so3 .02 neg. 8. Li+(C6H5)4B“ 0.51 0.0475 9. k+(c6h5)4b" 0.09 0.0125 10. (ch3)3fh+(c6h5) : 4b“ 0.08 0.011 * Solubility measured at 25°C 265 gave a negative iodide-starch test, indicating the absence of chlorine. When a small portion of it was shaken with distilled water., it caused the water to become acidic to pH paper. It was then extracted with 150 ml. water and then with 100.0 ml. of O.O87 N sodium hydroxide solution. The combined aqueous extracts were then titrated to phenolphthalein end-point with standard potassium acid phthalate solution (0.124 N) * „ requiring 45.2 ml. (cor responding to O.OO56 equiv.) of acid. The ethylene chlo ride solution therefore contained 0.0031 equivalents of ; acid. ; The precipitate in the remaining carbon tetrachlo ride solution was separated. It was too gummy for weight or melting point determinations and was therefore dissolved in acetone* (hot) and its crystallization (or solidifica tion) attempted. However* only gums of various consistencies were obtained. To the filtrate* which still gave a strong iodide-starch test* was added dimethylaniline (about 4 ml.); The solution immediately turned deep red (characteristic of the interaction'of I with dimethylaniline)* and after several days a negative iodide-starch test was obtained. The solvent was removed on the aspirator and the resulting j The solubility of this product In acetone is per- 1 haps the best evidence that it is not the disulfide* since the disulfide is almost completely insoluble in acetone. red oil crystallized from, absolute ethanol. A red-purple crystalline solid, weighed 1.05 g.* m.p. 178-180° (cor responding to 0.0033 moles of 2,4-dinitrophenyl 4-dimethyl- aminophenyl sulfide) was obtained. b. A solution of 8 g. (0.034 moles) I in 500 ml. carbon tetrachloride in a vycor flask was set in bright : sunshine for four and one-half days, after which it was , I chilled for four hours and filtered. A light brown solid, 1 weighed 0.86 g., was obtained. On the melting point ap- 1 paratus it began to darken at*150°, and became a black tar ; at 220-250°. The green filtrate from abov*e was allowed to ; stand for two weeks, during which time a precipitate slowly formed and the green color faded to yellow. A light tan solid which weighed 3.4 g. and on the melting point ap-, paratus blackened at 160-175° and melted to a black tar at ; 230-240°, was obtained. It was partly soluble in water to give an acidic yellow solution. A portion of it was dried in a vacuum desiccator and submitted for analysis Analysis: Found: C, 30.60; H, 2.66; Cl, 1.49. This analysis indicates that it is not a polymer of the 2,4- dinitrophenylthiyl radical, as this would require C = 36.2 , per cent, considerably more than the sum of the actual carbon and chlorine percentages. Apparently the substance ; I contains additional oxygen; it probably consists largely j of 2,4-dinitrobenzenesulfonic acid --_presumably.resuitingJ 267 from air oxidation of the 2*4-dinitrophenylthiyl radical. The presence of this acid would explain the partial water solubility (and the acidity of the solution produced)* as well as the low carbon content. The small amount of chlorine present may be due to products of ring attack by chlorine radicals, or may merely be caused by the presence of impurities, such as traces of solvent. The filtrate from above gave a positive iodide-starch‘ test, and a deep red color was obtained when dimethylaniline (6.2 ml.) was added. From this solution was obtained 2.85 g. (O.OO89 moles) 2,4-dinitrophenyl 4'-dimethylamino- phenyl sulfide, m.p. 176-I780, indicating the presence of * I in the original filtrate. c- Competitive Reactions. To obtain an indication of the relative reactivity of various compounds to I, the method of competitive reactions was utilized. Preliminary studies led to the following tentative table of reactivity (listed in descending order of reactivity). It Is possible that the reason that considerable amounts, of II did not decompose despite the long period of illumination is that, as the reaction proceeds, the solution becomes less and less transparent, preventing the sunlight from reaching the interior of the flask. 1. Morpholine 5. Styrene 2. Dimethylaniline 6. Ethanol i 3. Cyclohexene 7. Acetone j 4. Resorcinol 1 j i 1 The relative positions of dimethylaniline and cyclohexane i t ' ' (with respect to each other) are uncertain. The relative ! ! reactivities of several pairs of the above compounds were j ' ■ I studied quantitatively, but the results indicated that a ; > i , quantitative index could not be obtained, since the pro- i J I ducts not accounted for, or products which are impure, could ' shift the position of a compound on such an index consider- ! ! j ably. There are also the complications arising from the ^ i products of the reactions; in many cases hydrogen chloride j ; I ; is formed and it might be expected to inhibit the reaction j ! of amines, and possibly inhibit or catalyze the reactions ' i : ;of other substances. j ! Experimental. All substances used which are liquids j I ‘ ! :were distilled before use, the constant-boiling middle j I fraction being retained. Commercial absolute ethanol was j ! : used for recrystallizations. In the preliminary competitive i reactions a standard solution of I in ethylene chloride j 'was prepared and aliquots removed and added to ethylene I t ’ I ichloride solutions containing at least twice the equivalent I * j amount of each of the substances being tested. The solution ! ' i <_was_a 11 owed„to__remain_undisturbed_at_room_ temperature_untilJ 269 it gave a negative iodide-starch test. The solvent was then removed and the resulting oil (or solid) fractionally crystallized from ethanol. The quantitative studies were carried out as fol lows: A carefully weighed sample of freshly recrystallized I was dissolved in ethylene chloride in a glass stoppered flask. An ethylene chloride solution containing the two compounds whose relative reactivity was being determined was rapidly added, with stirring, and the solution allowed to stand at room temperature undisturbed until it gave a negative iodide-starch test. The solvent was then removed and the resulting oil (or solid) dissolved in hot ethanol and fractionally crystallized. The data for individual ex periments are summarized in Table CV. TABLE CV QUANTITATIVE COMPETITIVE REACTIONS Moles of Moles Moles Compounds used each I product % _____________________ taken_____taken_____found________ 1. Cyclohexene 0.0454 0.0160 87.0 0.0184 Styrene 0.0616 none* 0.0 Percent recovery of products 87.0 2. Cyclohexene 0.0406 0.0132 90.5 0.0146 Styrene 0.0541 none 0.0 Percent recovery of products 90.5 3. Cyclohexene 0.0402 0.00551 43.0 0.0128 Dimethylaniline 0.0386 0.00604 47.1 Percent recovery of products 90.1 4. Styrene 0.0324 0.01281 71 .'5 0.0179 Ethanol 0.0326 0.00488 27.2 Percent recovery of products 98.7 In neither of these experiments was any styrene adduct found. Since the styrene adduct has "been found to he less soluble than the cyclohexene adduct in ethanol, it might be expected that if any significant amount of styrene adduct were formed it would depress the melting point of the first crop of cyclohexene adduct.1 No such melting point depression was observed, and it may therefore be concluded that very little, if any, styrene adduct is formed. CHAPTER VII SUMMARY The reactions of sulfenyl halides with acetone (equation l) are formally related to the analogous reactions of the halogens with this ketone (equation 2). Because the latter reaction is one of the best studied cases in organic chemistry* the possibly similar but far less known reactions of equation 1 were selected — for comparative purposes — as the first in a series of studies concerned with the mechanisms of reactions of sulfenyl halides with various classes of organic compounds. The sulfenyl halides chosen were 2*4-dinitrobenzenesulfenyl chloride* I* and the corresponding bromide* II* and thiocyanate* III (the iodide is unknown and probably incapable of existence). 1. CH3COCH3 - t - RS:X = RSCH2COCH3 + HX 2. CH3COCH3 + X:X = XCHgCOCHg + HX Preliminary study showed the reaction between I and acetone (equation 1* R = 2*4-dinitrophenyl; X = Cl) to be essentially complete (95 per cent isolated product) under conditions suitable for rate determinations. The structure of the product* presumably 2*4-dinitrophenyl acetonyl sulfide* was confirmed by independent synthesis of this compound from 2*4-dinitrothiophenol and bromoacetone. An 272 iodometric titrimetric procedure was devised for the quantitative determination of the sulfenyl halides to be used and it was shown that the other substances present during the rate studies did not interfere with this analysis. Preliminary rate studies showed that the reaction ! between I and acetone -- with ethylene chloride or glacial ' acetic acid as solvent — and using approximately equiva- I I lent amounts of the two substances was too slow to follow | conveniently. For this reason large excesses of acetone j were used. When the acetone concentration was raised to ! 2.7 molar, 'which corresponds to about twenty volume per cent acetone in the solution, the half life of the reaction, was about twenty-four hours (temp. 26.5°) and the reaction ; , l was pseudo-first order with respect to I and shoxved the | same rate (within experimental error) in both ethylene ! chloride and acetic acid (k-^ = 0.028 hr.-' 1 '). In carbon I tetrachloride, however, the rate was appreciably slower j — 1 ! (k-^ = 0.019 hr.- ). Addition of anhydrous hydrogen chloride or p-toluenesulfonic acid did not change the ob- j served rate significantly. Addition of glass beads also j had no effect on the rate but the addition of lithium j t chloride caused a considerable increase in rate. It is j apparent, therefore, that the reaction between I and acetone in no way kinetically parallels the corresponding | react.ion„be_tween_chlorine_and__acet.one.j_whos.e _rate__is_________ 273 ; independent of halogen concentration and is greatly in- » • creased by added acid. i When the initial concentration of acetone was ; changed in an effort to obtain the order with respect to i i ; acetone, it was found that the observed rate changed by a i factor of five for a twofold change in acetone concentra- ; tion. This corresponds to an order with respect to acetone j ; of 2.3. However, twofold changes in the initial acetone i » f - - 1 , correspond to rather large'changes in the nature of the : 'solvent, and a considerable portion of the observed' vari- j 1 i ance in rate may be due to the changing nature of the I solvent rather than to a concentration effect. ' ; I ; It was therefore necessary to find a solvent in j which the reaction could be studied using equivalent amounts jof I and acetone. Numerous solvents were' tried. Methyl < j acetate was chosen as the one which gave the fastest rate ! j with, the least number of side reactions and complications, j i When kinetic studies were carried out in this solvent (at i 50° in sealed tubes} using equivalent amounts of I and j ! acetone, it was found that the reaction was first order. 1 * 1 ' Varying the amounts of I and acetone present showed that 1 - ! the reaction, during a given run, was first order with 1 respect to I and zero order with respect to acetone, but 1 ; that the first order rate constants obtained were almost j Lexactly .proportional to_the._initial_ac.e.tone__concentration.— 1 I This suggested that the rate was in some way being influenced by the products of the reaction. Each of the products was therefore added in turn to ascertain its effect on the rate. Added acetonyl sulfide had no signifi cant effect on the rate. However, when considerable amounts of anhydrous hydrogen chloride were added, not only did the j : rate increase, but the data also no longer fitted first ' ■ order kinetics but instead'plotted for second order. Vary-; i ing the relative amounts of I, Acetone, and acid (both hydrogen chloride and p-toluenesulfonic acid were used) ; showed that the reaction, with excess added acid present, : was first order with respect to both acetone and I, and that the rate was practically independent of acid concentra^ tion. Thus the addition of excess acid (one of the normal I products of the reaction) evidently produced either a i change in the mechanism, or in the rate determining step. I One possible explanation for all of these phenomena is the following mechanism: ; ki 4- a| ArSCl — ArS Cl" 4- kO b) ArS Cl + CH3COCH3 — ArSCH2COCH3 + HC1 The reacting species in the second step may be either acetone itself or its enol the two are kinetically i indistinguishable. (it was shown that, in methyl acetate, | 275 the rate of enolization of acetone is far greater than the rate of the reaction with I.) When there is no added acid, step a^ is presumed to be the rate determining step, leading to the observed first order kinetics. This ionization reac tion should be aided by any substance that can help remove f the chlorine, and such hydrogen bonding substances present as hydrogen chloride, acetone enol, protonated acetone, proton ated acetonyl sulfide, and protonated solvent should do this. Thus the actual rate expression for the first step should be: d(ArS+ )/dt = (I) [(k,(CHoC=$H) + k0(CHoC=GH0 ) JCH3 °h + k3 (CH3CCH3SAr) + k^(HCl). .+ k5 (CH3C=$H)] $H - ' °c h 3 Since the protonated species above are all formed from the nonprotonated substances in equilibrium reactions, one' can evaluate their concentrations in terms of the non protonated species. Doing this and substituting the result ; in the above kinetic expression (and combining the k^ and k^. terms) gives the following expression: d(ArS+ )/dt = (I) [ ( k ^ ^ C H ^ O C l ^ M H C l ) + kgKgtCI^COCI^) + k3K3(CH3COGH2SAr) + k^k^K^HCl) ] : The value for k2K2 can be determined from the ex pression kobg = k2K2 (CH3COCH3 ) which applies at the begin- - '276 : : ning of each run (when the hydrogen chloride concentra tion is zero), and was found to be 0.054. It was thought j that the values for the other three constants could be ob- I j ' I ; tained from the data of three runs in which limited amounts; of hydrogen chloride and acetonyl sulfide were added, but ' i j it was found that only the order of magnitude of the 1 constants could be obtained, since an error of only a few per cent in the rate constants led to deviations of several l ; hundred per cent in the values of the constants. . (This j occurs because the calculation of the constants involves ! I , the taking of differences between experimentally determinedi ? ‘ ■ values of almost equal magnitude.) A set of constants was 1 i evaluated which gave reasonably consistent sets of rate , 1 I I constants and checked well with the observed rate constants. When a considerable amount of excess acid is added, j ' ' . I i it is presumed that the rate of' the first step is increased! i l sufficiently that the second step becomes the slower of the i ; two, and thus the rate determining step, Step b as rate ; determining required, of course, that the reaction be ! i f : second order, first order with respect to I and to acetone,j i and that the rate be relatively independent of acid con- i i centration. All of these are observed when excess acid is J 1 . 1 j present. i : Studies carried out at temperatures other than 50° ! 1 I L_showed_that, _fqr_.the. first. .order_pr_ocess.,_the_ac.tivation i 277 energy was 10.5 kcal., and the entropy of activation -32.2 e.u. The activation energy and entropy for the second order process were 12.0 kcal. and -25.8 e.u. respec tively. The reaction of II with acetone was found to yield only a small.amount of acetonyl sulfide, the principal products being the disulfide and bromoacetone. Oxygen and diphenylmethane were found to have no effect on the reac tion, indicating that it does not occur by a free radical mechanism. The reaction quite possibly involves the at tack of "positive" bromine from the sulfenyl halide on acetone enol, producing the bromoacetone found and 2,4- dinitrothiophenol. Tiie thipphenol then reacts with sulfenyl bromide to produce the disulfide observed. The reaction of III with acetone in acetic acid and ethylene chloride is similar in nature but much slower than the reaction of I with acetone. Some insoluble polymeric material is also formed. In methyl acetate the principal product is this insoluble polymer, only a very small amount of acetonyl sulfide being formed. It thus appears that.the reactions of the three sulfenyl halides studied with acetone does not parallel the halogen acetone reactions. The reactions of I and III with acetone apparently involve electrophilic attack on acetone by a positive sulfur atom, whose formation is rate 278 determining. The reaction of- the sulfenyl thiocyanate is greatly complicated by its tendency to undergo condensation and polymerization reactions with the initial products of the reaction. The path or reaction of the sulfenyl bromide is apparently completely different. It appears that here the halogen atom is the positive end of the sulfur-halogen bond dipole, ■ and that the sulfenyl halide is acting as a positive halogen compound, with the bromine atom leading the electrophilic attack on acetone. This "changeover1 ' in bond polarization is possibly due to the closeness of sulfur and bromine in electronegativity (2.6 and 2.8 respectively), and that the dinitrophenyl group, by virtue of its inductive effect, may cause the sulfur to become more electronegative than bromine. BIBLIOGRAPHY REFERENCES 1. Allen, F. L., and Sugden, S., J. Chera. Soc., 440 (1936). 2. Ash, A., and Brown, H. C., Rec. of Chem Progress, 9, 81 (1948). 3. Assony, S. J., Private Communication. 4. Bartlett, P. D., and Small, G. J., Am. Chem. Soc., 72, 4867 (1950). 5. Bell, R. P., J. Chem.. Soc., 1774 (1939). 6. Bell, R. P., and Tantram, A. D. S., J. Chem. Soc., 370 (1948). 7. Blatt, A. H., (Editor), Organic Synthesis, Collective Vol. 2, J. Wiley & Sons," Inc. ,' 'New York, l9'43~, p . 88. 8. Blatt, A. H., (Editor), Organic Synthesis, Collective Vol. 2, J. Wiley & Sons, Inc., New York, 1943, p. 455. 9. Btfhme, H., and Schneider, E., Ber., 76, 483 (1943). 10. Bost, S. W., J. Am. Chem. Soc., 73, 19^8 (1951). 11. Brendler, W., and Tatel, J., Ber., 31, 2683 (1898). 12. Buess, C. M., and Kharasch, N., J. Am. Chem. Soc., 71, 3529 (1950). 13. Cathcart, W. H., Treadway, R. H., and Briscoe, H. T., Proc. Indiana Acad. Sci., 48, 92 (1939). 14. Christiansen, J. A., Z. Physik, Chem., 33B, 145 (1936); 37B, 374 (1937). 15. Crowell, W. R., Notes on Quantitative Analysis, Edwards Bros. Inc., Ann Arbor', Mich", 1942, p. 193 ff. 16. Dawson, H. M., and Spivey, E., J. Chem. Soc., 2180 (1930). 17. Falciola, P., Atti. acc:ad. Lincei, 17 II, 324 (1908). 18. ' 19. 20. 21. 22. . 23. 24. 25. 26. . 27. 28. . 29. 30. , 31. 1 32. 33. 34. ' 2 8 1 Fialkov, Y. A., and Kleiner, K. E., J. Gen. Chem. (U.S.S.R.), 11, 671 (1941); C.A., 35, 7307 (1941). Pieser, L. F., Experiments in Organic Chemistry, 2nd Edition, C.’ D. Heath & Co.V Mew York,' T^4i, p. 364. Pieser, L. P., J. Am. Chem.'Soc., 46, 2639 (1924). Poss, 0,, Acta. Chem. Scand., 1_, 310 (1946). Pries, K., and Schumann, G'., Ber., 47, 1195 (1914). Prost, A. A., and Pearson, R.- G., Kinetics and Meehan- . ism, J. Wiley & Sons, Inc., New York, 1953, P- ‘ 9T~ff. Harned, H. S., and Owen, B. B., The Physical Chemistry ; of Electrolytic Solutions, Reinhold Publ. Co.', New'York, 1943, p. 1$6 ff. Havlik, A. J., Ph.D. Dissertation, Univ. of So. Calif., 1954. Havlik, A. J., Private Communication. Hurd, C. D., and Kharasch, N., J. Am. Chem. Soc., 68, ; 656 (1946). Gilkerson, W. R., Argersinger, w. J., and McEwen,' W. E., J. Am. Chem. Soc., 76, 41 (1954). Goodman, L., Private Communication. a. Kharasch, N., Buess, C. M., and Strashun, S. I., J. Am. Chem. Soc., 74, 3422 (1952). b. Kharasch, N., and Buess, C. M., J. Am. Chem. Soc., 71, 2724 (1949). Kharasch, N., Gleason, G. I., and Buess, C.M., J. Am. Chem. Soc., 72, 1796 (1950). • Kharasch, N., and King, W., Unpublished Work. ' Kharasch, N., McQuarrie, D. P., and Buess, C. M., J. Am. Chem. Soc., 75, 2658 (1953). Kharasch, N., Potempa, S. J., and Wehmeister, PI. L., _ Chem._ Re.y..39, -269 .(1946) _____...... ..______i 282 35- Kharasch, N., Wehrmeister, H. L., and Tigerman, H., J. Am..Chem. Soc., 69, 1612 (1947). 36. McQuarrie, D. P., Masters Thesis, Univ. of So. Calif., 1952. 37- Migrdichian, V., The Chemistry of Organic Cyanogen Compounds, Reinhold’ "Pub’ l. Corp., New York, 1947 , p. 864 fF. 38. Mitchell, J. A., and Reid, E. E., J. Am. Chem. Soc., 53, 1879 (1931). 39. Newman, M. S., J. Am. Chem. Soc., 73, 4993 (1951). 40. Orr, W. L., and Kharasch, N., J. Am. Chem. Soc., 75, 6030 (1953).. ~ 41. Pauling, L., The Nature of the Chemical Bond, Cornell Univ. Press, Ithaca, New"7ork, 1940. 42. Pearson, R. G., J. Chem. Phys., 20, 1478 (1952). 43. Ramsey, J. B., Colichman, E. L., and Pack, L. C., J. Am. Chem. Soc., 68, 1695 (1946) and earlier papers. 44. Rheinholdt, H., and Perrier, M., Bull. sioc. chim. France, 759 (1950). 45. Rice, F. 0., and Fryling, C. F., J. Am. Chem. Soc., 47, 379 (1925). 46. Rice, F. 0., and Kilpatrick, J. Jr., J. Am. Chem. Soc., 45, 1401 (1923). 47. Schonherg, A., Trans. Far. Soc., 30, 17 (1934). 48. Schonherg, A., and Mustafa, A., J. Chem. Soc., 889 (1949). 49. Schonherg, A., and Rupp, E., Naturwissenschaften, 21, 561 (1933). 50. Schotte, L., Acta Chem. Scand., 4, 1304 (1950). 51. Schwartzenhach, G., and Wittwer, C., Helv. Chim. Acta.,' 30, 669 (1947). 283 52. Swain, C. G., and Brown, J. P., J. Am. Chem. Soc., 74, 2534 (1952). 53* Shriner, R. L., and Fuson, R. C., The Systematic Identification of Organic Compound's," 2nd' Edition, J. Wiley and Sons, New York, 1935» P* 65. 54. Steelink, C., Masters Thesis, Univ. of So. Calif., 1950. 55- Steiner, H., and Watson, H. R., Disc. Par. Soc., 2, 88 (1947). 56. Strashun, S. I., Masters Thesis, Univ. of So. Calif., 1948. 57. Swain, C. G., J. Am. Chem. Soc., 72, 4578 (1950). 58. Swain. C. G., and Brown, J. P., J. Am. Chem. Soc., 74, 2534 (1952). 59. Swidler, R., Masters Thesis, Univ. of So. Calif., 1951. 60. Swidler, R., and Kharasch, N., Unpublished Work. 61. Szmant, H. H., Harnsberger, H. P., and Krahe, P., J. Am. Chem. Soc., 76, 2185 (1954). 62. Vorlander. D., and Mittag, E., Ber., 52B, 413 (1919). 63. Washburn, E. W., (Editor), International Critical Tables, Vol. 6, McGraw-Hill Book Co., New York, 1929"; p.nST. - 64. Wittig, G., Ann., 573, 195 (1951). . 65. Zincke, T., Ber., 44, 769 (1911 )• 66. Zincke, T., and Baeumer, J., Ann., 4l6, 86 (1918). 67. Zincke, T., and Rose, H., Ann., 406, 103 (1914). 68. Zucker, L., and Hammett, L. P., J. Am. Chem. Soc., 61, 2791 (1939).

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Alpha nitro sulfides and related studies

PDF

A study of the reaction of 2,4-dinitrobenzenesulfenyl chloride with the cis- and trans-stilbenes

PDF

A study of the kinetics of the reaction of sulfenyl halides with olefins

PDF

A study of the structures and properties of triaryl compounds of boron

PDF

A new synthesis of thiophenols

PDF

A study of the activation of hydrogen by cuprous salts in quinoline / by Max K. Barsh

PDF

A study of the interactions of polar gases with solid proteins and some simple organic compounds

PDF

A study of the reaction of tetramethyldiborane with sodium in liquid ammonia and the products derived from this reaction

PDF

A determination of ionic diffusion coefficients

PDF

Application of the Hammet equation to the dissociation of the substituted 1,1,4,4-tetraphenyl-2,3-dibenzoyltetrazanes.

PDF

Addition compounds of boron fluoride with certain sulfoxy-amines

PDF

A study of chemical tests for the vitamins

PDF

2-nitrobenzenesulfenyl thiocyanate and 2,4-dinitrobenzenesulfenyl thiocyanate

PDF

Colloid properties of some New Mexico clays

PDF

Kinetics Of The Basic Hydrolysis Of Ring-Halogenated Ethyl Phenoxyacetates. Free Radical Attack On Acids And Amides

PDF

Pyrrolenines And Their Derivatives From The Reduction Of Gamma-Nitro Ketones

PDF

A kinetic study of the radioactive exchange between potassium ferrocyanide and potassium cyanide

PDF

Competitive antagonists of thyroxine and structurally related compounds

PDF

An experimental investigation of gas phase synthesis using a spark generated shock wave

PDF

Chemical, physicochemical, and biological studies on the mucoproteins of plasma and serum

Asset Metadata

Creator Wald, Milton M (author)

Core Title A study of the reaction of 2,4-dinitrobenzene-sulfenyl halides with ketones

Degree Doctor of Philosophy

Degree Program Chemistry

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, organic,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Kharasch, Norman (committee chair), [illegible] (committee member), Brown, Ronald J. (committee member), Copeland, C.S. (committee member), Visser, Donald (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c17-620349

Unique identifier UC11353933

Identifier DP21777.pdf (filename),usctheses-c17-620349 (legacy record id)

Legacy Identifier DP21777.pdf

Dmrecord 620349

Document Type Dissertation

Rights Wald, Milton M.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA