In presenting the dissertation as a partial fulfillment of the requirements for an advanced degree from the Georgia Institute of Technology, I agree that the Library of the Institution shall make it available for inspection and circulation in accordance with its regulations governing' materials .. of -this type. I agree that permission to copy from, or to publish from, this dissertation may be granted by the professor under whose direction it was written, or, in his absence, by the Dean of the GralUate Divisibn when such copying or publication is solely for scholarly purposes'and does not involve potential finan, cial gain. It is understood that any copying from, or publication of, this dissertation which involves potential financial gain will not be allowed without written permission. THE MECHANISM OF THE BASIC HYDROLYSIS OF HAIDFORMS A.THESIS Presented to the Faculty of the Graduate Division by Arthur Maultsby Dowell, Jr. In Partial FulfillMent of the Requirements for the Degreee Doctor of Philosophy in Chemistry GeCTgia Institute of Technology June, 1954 THE MBC*NISM: OF THR BASIC HYDROLYSIS OF HALOFORMS Approved: I h' 11J f • Date approved by ChafrmanT ) /9.5-171 • ii ACKNOWLEDGMENT I wish to express my appreciation to Dr. Jack Hine for his suggestion of the problem and his valuable aid and guidance during its progress. I also wish to thank the National Science Foundation and the Graduate Division of the Georgia Institute of Technology for granting me fellowships. I wish to thank my wife and children for their patience and encouragement, without which I could never have completed this work. TABLE OF CONTENTS Page ACKNOWLEDGMENTS ii LIST OF TABLES iv LIST. OF ILLUSTRATIONS • • • •• • • • .• • • **** * . ' • 0 ' • viii SUMMARY ix Chapter INTRODUCTION . 2 II METHOD OF ATTACK 6 III ,EXPERIMENTAL 9 Kinetic Runs Isolation of Dicaoroiodomethane Determination of FactOrjf Isotopic Ratio in the:Formate Produced Prepration and PurifiCation of Reagents IV DISCUSSION OF RESULTS 23 V CONCLUSIONS 45 APPENDIX 46 BIBLIOGRAPHY 89 VITA 92 iv LIST OF TABLES Table Page 1. Preparation of Runs 13 2. Deterudnation of f „. • .• • • • • ,• ,• z• • • ,• • •,• • , • 17 3. Rate Constants ,for the Hydrolysis of ,Chloroform in the Presence of 0.160 N Added Salts and 0 .0353 . 7 . a a a a . a , . a a. • 23 4. Rate Constant Ratiostor,the,gydrolysis of Chloroform , in the Presence of 0.160 !Added Salts and 0.0353 N NaOH 25 5. Rate Constants for the BYdraYSis of Chloroform in the Presence of 0.080 N Added Salts and 0.019 N NaOH • OOOO • 0 • • • ••• • • 0 • , • • • • • a • • • 26 6. Values of 0( for Halide Ions with Carbon Dichloride at 0.080'N Aded SAlt and 0.019N NaOH 32 7. cx: x at 0.160 N Salt and 0.0353 N NaOH 33 8. 0< x at 0.20 N Added Salt, 1.5 N NaC104, and 0.19 N NaOH 34 9. Rates of Hydrolysis ,of Haloforms . ....... ..... 40 10. Heats and Ehtropies of Activation for Haloforms. • , 0 • • • 43 11. Standard Haloform Solhtions . 47 12. Run Chloroform in. the Presence of 0.160 N Added Salts at 35.0° 48 13. Run B. Chloroform in the Presence of 0.160 N Added Salts at 35.0 ° 49 14. Run D. Chloroform in the Presence of 0.160 N Added Salts at 35.0 ° ..... • . • . .. .. 15. Run F. Chloroform in the Presence of 0.160 N Added Salts at 34.9° 51 16. Run L. Chloroform in the Presence of 0.080 N Added Salts at 34.9 ° 52 LTST OF' TABLES (Continued) Table Page „ . 17. Runs EH, PI, and EJ. Chloroform in the Presence of 0.080 E Added Salts at 35.0 ° . 53 18. Runs. BK, BL, and,BM, Chloroform in the Presence of 0.080 H:Added. Salts at 34.9° . • OOOOOOOO • • • 54 19. Runs EN, BL), and EP. Chloroform in the Presence of 0.080 2: Added Baits at 34.92° ••. OOOO • • • 55 20. Runs; AK, AL, and AM. .Chloroform inthe,presence of 0.080 N Added Salts at 35.0° 56 It 21. Runs pa and BR. Chloroform in.the Presence. of 0.058,N Sodium p-Thiocresolate at34.95 ° 57 22. Run DEL Chloroform in, 67 Per Cent : Dioxane at 34.95°. • • 58 23. Run U. Chloroform in 67 Ter , Cent Dioxane at 35.0 ° . 59 24. RUn V. ChlorofOrmln 67 Per dent Dioxane at 35.0 ° . 60 25. Run AC. iChloroform.in Water' at 35.0 ° ' 61 26. Run,AD.. Chloroform in W474er at.35.0 ° 62 27. RUn AE. Chloroform in 40 Per Cent.Dioxane at 35.0 ° . • • 63 28. Run AF.. Chloroform in 40 -Per Cent Dioxane at,35.0 ° . • • 64 29. Run AG. Chloroform in 40 Per Cent Dioxane at 35.0 ° . • • 65 30. Runs AS and AT. Chloroform in Water at 0.0 ° 66 31. Runs AY and AZ. ChlorofOrm in Water at 0.0° 67 32. Run AU. Chloroform in ,66-2/3 Per Cent Dioxane at 0.0 ° • 68 33. Run AV. Chloroform in 66-2/3 Per Cent Dioxane at 0.0 ° • • 68 34. Run.P. Dichlproiodomethane in 67 Per,Cent Dioxane at 34:95° 69 35. Run S. sDichloroiodomethane,ic 67,Per Cent Dioxane at 35.0° 70 vi LIST OF TABLES (Continued) Table Page 36. Run W. Dichler4odamethane in 67 Per Cent Dioxane at 35.0° .... .. • ,. • • • .. ,. „ . , 71 37. Nun X. Dichloroiodomethane in 40. Per Cent, 72 Dioxane at:55'.0 ° • • • . .- . • .. ,• - • , . , ,. =. 38. Run r. Dicblor4odometbane - in 40 Per Cent Dioxane ,• • • • • • • 73 39. Run AA. .'Dialoroiodo4t4ans,in ,. , 40 Psr„Cent ,Dioxane at' 35.0° . „: o _ • '. o • • T .... , • • o•, a 74 40. 4an AO. Dichlor4odometbane in Water at 35.0° 75 41. Run AP. DichloroiOdot6thape4a Water at 35.0 ° 76 42. Run AW. Dichloroiodothethane in 66-2/3 Per Cent Dioxane at 0.0 ° - 77 43. Run. AX„ Diebloroiodometbandin 6642/3 Per Cent • Dioxane at 0.0 ° 78 •, AA . , . 44. Run Al. 2VomochloraluordAsthane in 66-2/3 Per Cent DioXane at ' 0.0 ° . ... • . , . - • . 79 45. Run AJ. Bromosblorofluorametbane in 66,2/3 Per Cent Dioxane at 0.0 ° 80 . , . 46. Run AN. BromochlOrofluormsethane in Water. at 0.0 ° • • • • 81 47. Run AQ: B4,amOchlorofluOromethane in 40 Per Cent Dioxane - at 0,0° 82 48. Run AR. Br§mochloraluoromethane in 40 Per Cent, Dioxane at 0.0 ° 83 49. Runs BB and BG. Bromoehlorofluoromethene in 66-2/3 Per Cent Dioxane at 14.3° 84 50. Run BC. Dibromoehloromethane in 66,2/3 Per Cent Dioxane at 0.0 ° . ..... .. • • . • • • • 85 51. Run BD. Dibromoehloromethane in 66-2/3 Per Cent Dioxane at 0.0 ° 86 vii LIST. OF TABLES (Continued Table Page 52. Runs BE and p'. DiehlorobrOmpethane in 66-2/3 Per Cent Dioxane at o.o° .. , . - • . .. , • 87 53. Run BS. Fluoroform in. Water at 50 0 88 viii LIST OF ILLUSTRATIONS Figure Page 1. Rate of Hydrolysis of Chloroform in the Presence of 0.160 N Nal and 0.0353 E NaOH . ... .. - • - . • - 24 2. Rate of Hydrolysis of chloroform in the Presence of 0.080 11:1114I and 0.019 N NaOH 27 3. Rate of Hydrolysis of Chloroform in the Presence of 0.080 N NaBir and 0.019 N NaOH 28 4. Logo< versus n for Carbon Dichloride 35 ix SUMMARY Although it was previously shown that the basic hydrolysis of chloroform probably proceeds by a mechanism involving the trichloro- methyl carbanion and carbon dichloride as intermediates, it was not possible to prove conclusively that the reaction does not proceed either by the 5N2,attack of water molecules upon the trichloromethyl anion or by the SN2 attack of hydroxide ions upon chloroform. Since the carbon dihalide mechanism involves the loss of a chloride ion from the trichloromethyl anion by an Snl reaction in the rate determining step, it was believed that demonstration of a mass law effect would offer conclueive proof.. of the., carbon dihalide mechanism. Atcordingly, the rate of basid' , hydrolysis of chloroform'itras determined in the presence of several added salts at several concentrations. Although the effects of sodiuM fluoride, nitrate, and perchlorate upon the rate of this reaCtion'differed by amounts within the experimen- tal error, the reaction was slowed by identical concentrations of chloride, brotide l and iodide ions. In the case of sodium chloride, this waS"due to a mass law effect'produced by the recombination of carbon di- chloride with chloride ions. ConbinatiOn of carbon dichloride with bromide and iodide ions yielded dichlorobromomethane and dichloroiodo- methane, the latter compound having been isolated: In agreement with expectation, the rate constants obtained in the presence of bromide and iodide ions climb with time because the haloforms produced by the reactions of these ions with carbon dichloride are more reactive than chloroform. Good agreement was found between the magnitude of the de- crease in the initial rate of chloroform hydrolysis due to the inter- vention of the various halide ions and the nucleophilic constants of the halide ions according to Swain and Scott. These data rule out all of the alternate mechanisms which have been suggested. The rates of basic hydrolysis of chloroform, dichloroiodomethane, dichlorobromomethane, chlorodibromomethane, and bromochlorofiuoromethane have been determined in aqueous,dioxane. The kinetics in all cases was first order in both haloform and , hydroxide ion. The relative reactivity toward =sodium hydroxide in aqueous dioxane was found to be HCErC1F > HCC12Br > HCC1Br2 HCC12I > HCC13 > HCF3 . Heats and entropies of activation have been calculated frOm' the observed rate constants. MECHANISM OF THE 'IAA.= HYDROLYSIS OF HA:Lokiltis , CHAPTER I INTRODUCTION Although Geuther (1) was probably the first to suggest that carbon dichloride is an intermediate in the basic hydrolysis of chloro- form, the first good evidence for the existence of this compound as an intermediate was presented by Hine (2) as the result of a kinetic study of the basic hydrolysis of chloroform in aqueous dioxane.