Presented to the Faculty of the Graduate Division by Robert John Rosscup in Partial Fulfillment of the Requirements for the Degr
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REACTIVITY AM) REACTION MECHANISM S OF mummy CHIAORIDES A 'ES IS Presented to the Faculty of the Graduate Division by Robert John Rosscup In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry Georgia Institute of Technology March, 1960 g 4 AND REACTION ItECHAEISMS OF METHOXY CHLORIDES Approved: _ • - 1-1[ - 117 {] Er ii ACKNOWLEDGEMENTS I would like to extend my sincere appreciation to Dr. Jack Hine for his suggestion of this-problem and for his continued interest in its imPlementation. In addition a debt of gratitude is due him for the benefits I have derived from his willingness to share his knowledge and understanding of chemistry. I would also like to express my thanks to Dr. Erling Grovenstein, Jr. and Dr. Henry Neumann for having, served on the reading committee. To the American Viscose Corporation, the Rayonier Corporation and the Alfred P. Sloan FOundation I am very grateful for financial aid that supported my graduate study. Above all I gratefully acknowledge the encouragement and assistance from my wife, without which this undertaking could not have been completed. iii TABLE OF PATENTS Page ACENOMEDGEMENTS LIST OF TABLES LIST OF ILLUSTRATIOES 0 0 0 0 0 0 . 0 0 0 0 0 0 0 OOOOO • 0 vii SUMMARY 0 OOOOOO 0 0 Ik 0 0 • 0 viii Chapter I. IDIRODUCTION 1 II. PROCEDURE O OOOO 0 O 0 OOO 0 12 Attempted Preparation of Trichloromethylamine 12 Preparation of Methyl Dichloromethyl Ether. 15 Preparation of Bis-Nethoxytblocarbonyl)Disulfide . • • 15 Preparation of Methyl Trichloromethyl Ether 16 Preparation of 21.-Methoxybenzal Chloride • • . OO . OO 16 Preparation of 2-Metboxybenzyl Chloride 17 Preparation of Formic-d-Acid-d. • . • 0 0 OO 18 Preparation of Methyl Formate-d 19 Preparation of Methyl Dichloromethyl-d Ether 19 Reactivity of Methyl Monochloromethyl Ether 21 Reactivity of Methyl Trichloromethyl Ether 22 Reactivity of Methyl Dichloromathyl Ether . 23 Comparative Reactivity of Methyl Dichloromethyl Ether and Methyl Dichloromethyl-d Ether 27 Reactivity of 2-Methoxybenzyl Chloride 28 Reactivity of 21.-Methczybenzal Chloride 30 Reagents. 31 Infra -Red Measurements. OO . • . OOOOOO 0 33 III. RESULTS .... 0 0 9 OOOOOO a 0 0 0 0 0 0 • • 35 Solvolysis of Chioromethyl Ethers 35 Reaction Rates of Methyl Dichloromethyl Ether in Isopropanol . 37 Comparative Reactivity of Methyl Dichloromethyl Ether and Methyl Dichloromethyl-d Ether 41 Reaction Rates of 24Metboxybenzyl and 2.-Methoxybenzal Chloride 42 Identification of Products in the Attempted Preparation of Trichloromethyl Arnim. 0 . • • • . 44 Page IV. DISCUSSION AND CONOLUSIONS 47 Solvolysis of Methcocy Chlorides 47 The 0(-Elimination Reaction of Methyl Dichloromethyl Ether. • . • . 62 V. RECOMMENDATIONS 69 APPENDIXA.. OOOOOOOOO • • 73 APPENDIX B • 67 APPENDIX C. C . 110000000400601,000 00 O0 95 BIBLIOGRAPHY. ••••••••••••• 101; VITA• • • • • . ........ • • ..... • 109 LIST OF TABLES Table Page 1. Rates of Hydrolysis at 30 0 2 2. Rate Constants for Solvalysis of Chloromethyl Ethers in Ethanol-Ether at 00 ..... . , 36 Comparison of the Quantities of Acid and Chloride Ion Produced in the Solvolysis of Methyl Dichloromethyl Ether . 37 4. Comparison of the Quantities of Acid and Chloride Ion Produced in the Solvolysis of Methyl Dichloromethyl Ethpr . 38 5. Reaction of CH3OCHC12 with Potassium Ipopropoxide 40 6. Comparative Reactivity ofCH3CCDC12 and oycga2 with Potassium Isopropoxide 42 7, Solvolysis of rCH30C6H4CHC12 in 5:1 Acetone Water at 30° 4 • 44 8. Infra Red Absorption Maxima in Microns. . .. 45 9. Solvolysis of CH30CH2C1 in Ethanol-Diethyl Ether at .., • • 74 10. Solvolysis of pyp2c1 in EthanolDiethyl Ether at 6° . • . 74 II. Solvolysis of CH OCC1 3 ini Eh tanol-Eh ter at 00 3 75 12. Solvolysis of CH3OCHC12 in Ethancil-Ether at 0 ° 76 13. Solvolysis of CH OCHC1 it Ethanol-Diethyl Ether at 0° . 76 3 2 14. Solvolysis of cycnci2 in Isopropanol at -14 f 0.5° 77 15. Solvolysis of CH3OCHC12 in Isopropanol at -12 ± 0.50 77 16. Solvolysis of CyCHC12 in t-Amyl. Alcohol at 0° 78 17. Reaction of CRq0CHC12 with Potaesiumt-Amyloxide in t-Amyl. Alcohol at 0° ' 79 18. Comparative Reactivity of CH OCDC1 and OCHC12 with Potassium Iscpropoxide 3 80 19. Solvolysis of 2.--CH3OCACH2C1 in 5:1 Acetone Water at 30° . 81 Table Page 20. Solvolysis of 21.-CH30C6E4CHC12 in 5:1 Acetone Water at 300 . 82 21. 30C6H4CHC12 Solvolysis of 2-CH in 5:1 Acetone Water t 30o . 83 300 22. 30C6H4CHC12Solvolysis of 2701 in 5:1 Acetone Water at . 23. 30C6H4C4C12 Solvolysis of 2-CH in 5:1 Acetone Water at 300 . 85 24. Solvolysis of g-01 10C6Hh HC12 in 5:1 Acetone Water in the Presence of Added Chloride 86 25. First. Order Rate Constants at Zer Ionic Strength and Mass -law Constants 26. First Order Rate Constants at Zero Ionic Strength and Mass-law Constants 98 vii LIST OF ILLUSTRATIONS Figure Page 1. _Potential'Energy Diagram. 48 2. Infra-red Spectrum of Hofmann Reaction Product. .. .. 88 3. Infra-red Spectrum of Hofmann Fraction 2 ..... 88 4. Infra-red Spectrum of Methyl Trichloromathyl Ether 89 5. Infra-red Spectrum of 21:-Methoxyben;a1 Chloride 89 6. Infra-red Spectrum of 11.-Methozybenzaldebyde,. 90 7. Infra-red Spectrum of pi:MethacYbenzyl Chloride 90 8. Infra-red Spectrum of 2.-Mathoxybenzyl Alcohol 91 9. Infra-red Spectrum of Partially Deuterated Methyl Formate 91 10. Infra-red Spectrum of Methyl Formate 92 11. Infra7red Spectrum of Partially Deuterated. Methyl Dichloromethyl Ether, ... o . ...... • • • • 92 12. Infra-red Spectrum of Partially Deuterated Methyl DichloromethyI Ether. , . , . • , 0 0 0 - 0 .. 0 ... 93 13. Infra-red Spectrum of Methyl Dichloromethyl Ether 93 14. Infra-red Spectrum of Methyl Dichioromethyl Ether 94 15. Infra-red Spectrum of Trichlorobromomethape . 0 . • . • • . 94 16. Graphical Determination ofce and lc! • . • . , • • . 102 17. Graphical Determination ofce and . .. * .. 103 viii SWIM' The effect of 0(-halogen on the reactivity of other halogen atoms attached to the same carbon atom has been elucidated by previous workers for some phenylhalomethanes. It was found that added chlorine or bromine increased the Sigl reactivity. This enhanced reactivity was attributed to a resonance interaction between the O(-halogen and the electron deficient carbon atom of the incipient carbonium ion that tended to lower the energy of activation. Thua a structure with a positive charge on halogen contributes to the total structure of the carbonium ion. /X -C-H - C - H It was established that chlorine was better than bromine at enhancing the Snl reactivity in spite of the fact that chlorine is more electro- negative. Therefore, it appeared that the predominate electrical effect of the added halogen was a resonance interaction of electron donation rather than an inductive withdrawal of elections. Since chlorine has orbitals which are more similar energetically and comparable in size than bromine to the unoccupied orbital of the positively charged carbon atom of the carbonium ion, C-chlorine would be expected to exhibit the larger resonance interaction. In the present investigation, however, it has been found that the SNI reactivity, in la diethyl ether-ethanol, of Methyl chlorOmethyl ether and methyl dichloromethyl ether is reduced by thOubstitution of ix 0(-chlorine for O(-hydrogen. For example, methyl dichlotomethyl ether was found to be 80 times less reactive, per chlorite, than was methyl chioromethyl ether. The methazy group, which is common to both com- pounds, can affect the rate of ionization several ways, by an electron withdrawing effect which will tend to decrease reactivity, by resonance stdbilization of the carbonium ion which will tend to increase the reactivity and by resonance stabilization of the reactant which will tend to decrease the reactivity. The reactivity of all the chloromethyl ethers shows that the inductive effect of the methoxyl group is not predominate and that the resonance stabilization of the carbonium ion is important. But these two effects should be the same for both the ethers. Therefore, resonance stabilization of the reactant may explain the observed decrease effected by O(-chlorine. Thus contributions of structures such as ,H CH3 0= C\ Cl - Cl 2 equivalent forms to the total structure of the reactant are of importance in determining changes in reactivity. The first order solvolyses of 11.-metboxybensyl chloride and 2-methoxybenzal chloride have been investigated in a solvent composed of acetone and water present in a volume ratio of 5:1. In this case, OEchlorine did not effect a decrease in reactivity, but the increase was somewhat less than the increase observed in going from benzal chloride to benzotrichloride. By analogy with the chloromethyl ethers, it is x suggested that contributions of ionic structures to the total structure of the reactant is responsible for this smaller increase in Sill reactivity. The base catalyzed solvolysis of methyl dichioromethyl ether has also been investigated. This compound is of interest because it is a possible intermediate in the methoxide catalyzed methanolysis of chloroform. If the manner by which methyl dichioromethyl ether undergoes base catalyzed solvolysis can be ascertained, it could lend support to the suggestion that dihaloethers or alkoxyhalomethylenes are intermedi- ates in the base catalyzed solvolysis of haloforms. The two possible reaction paths are (1) nucleophilic attack by base on carbon with the concurrent loss of chloride ion, commonly referred to as Se, or (2) nucleophilic attack by base on hydrogen with the concurrent, or subse- quent, loss of chloride ion to form methoxychloromethylene which then reacts rapidly with the solvent. The latter path has been designated as 0k-elimination. Previous workers have shown that the substitution of 0(-chlorine for (X-hydrogen results in a decrease in second order reactivity in those cases where the mechanism is known to be S n2. The observed decreases have varied from 30 to 1,000 fold. However, when the intro- duction of (A-chlorine results in a compound that can react by the alpha- elimination mechanism, it is accompanied by a considerable increase in second order reactivity.