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THE INFLUENCE of SUBSTITUENTS on the Cis-Trans ISOMERIZATION of AZOBENZENE

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THE INFLUENCE of SUBSTITUENTS on the Cis-Trans ISOMERIZATION of AZOBENZENE THE INFLUENCE OF SUBSTITUENTS ON THE cis-trans ISOMERIZATION OF AZOBENZENE DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By ERACH RUSTOMJI TALATY, B. Sc. (Hons.), M. So. ****** The Ohio State University 1957 Approved by: Adviser Department of Chemistrj ACKNOWLEDGMENTS The author wishes to express his deep sense of grati­ tude to Dr. Earl W. Malmberg for invaluable help and guid­ ance throughout this investigation. It was mainly through his kind efforts that it was possible for the author to come to the United States of America and study at this univer­ sity, and for his kindness in this and in many other ways, the author is permanently indebted to him. The author also wishes to thank the Research Corpora­ tion very much for a Research Fellowship that was awarded to him for two years, namely, from October, 1954, through September, 1956. Without this timely help, it would have been well-nigh impossible for the author to maintain himself in this country. Sincere thanks of the author are due to E. I. du Pont de Nemours and Company, too, for the grant of a Research Fellowship during the Summer Quarter of 1957* Finally, the author would like to express his indebted­ ness to Mr. S. Ramachandran and to Mr. Paul Anthony for the spontaneous assistance that they gave so generously in cal­ culations and proof-reading, respectively; to Mrs. Rosalie Kishler, Mrs. Diane Uhler, Mrs. Jane Scott, Mrs. Esther Salisbury and Miss Mary Morley, without whose voluntary and ii Ill valuable help, this dissertation would not have been typed in the required time; and to his fellow graduate students and other friends for help at various times in manifold ways. TABLE OP CONTENTS Page I . INTRODUCTION.......................... 1 II. STATEMENT OF THE PROBLEM.............. 15 III. RESULTS AND DISCUSSION................ 15 A. Synthesis of the Necessary Compounds 15 1. Preparation of trans forms 15 2. Preparation of cis forms 21 B. Absorption Spectra of the Azo Compounds.......................... 25 C . Measurement of the Rates of Isomerization...................... 29 IV. EXPERIMENTAL A. Materials 1. Adsorbent..................... 50 2. Solvents...................... 50 B. Synthesis of trans Forms of Sub­ stituted Azobenzenes 1. Preparation of nitrosobenzene.... 52 2. Preparation of 4-chloroazobenzene (a) From 4-aminoazobenzene 54- (b) By condensation of nitroso- f benzene with 4-chloroaniline 55 5. Preparation of 4-iodoazobenzene... 56 iv Page 4. Preparation of 4-cyanoazobenzene (a) From 4-arainoazobenzene...... 57 (b) By condensation of nitroso­ benzene with 4-aminobenzo- nitrile..................... 58 5 . Preparation of 5-chloroazobenzene. 59 6. Preparation of 5-iodoazobenzene... 59 7. Synthesis of 5-cyanoazobenzene (a) Preparation of 5-aminobenzo- nitrile (i) Attempted catalytic re­ duction of 5-nitro- benzonitrile........... 6l (ii) Reduction of 5-nitro- benzonitrile with stannous chloride....... 6l (b) Condensation of nitrosobenzene with 5-arainobenzonitrile.... 62 8. Preparation of 4-bromoazobenzene.. 6^ 9. Preparation of 5-bromoazobenzene.. 64 10. Preparation of 4-fluoroazobenzene. 65 11. Preparation of 5-fluoroazobenzene. 65 12. Preparation of 4-methoxyazobenzene 67 1 5 . Synthesis of 5-niethoxyazobenzene (a) By condensation of nitroso­ benzene with m-anisidine 67 (b) Prom o-anisidine (i) Preparation of 5-methoxy- 4-aminoazobenzene....... 68 (ii) Deamination of 5-methoxy- 4-aminoazobenzene 70 V Page l4. Preparation of 4-nitroazobenzene.... 71 15» Preparation of 2-nltroazoLenzene.... 71 16 . Preparation of (4-phenylazophen'yl) trlmethylammonlum nitrate (a) In nitrobenzene as solvent 72 (b) In dlmethylformamlde as solvent 72 1 7. Synthesis of (2-phenylazophenyl) trlmethylammonlum nitrate (a) Preparation of 3-amlnoazobenzene 75 (b) Méthylation of 5-amlnoazobenzene 74 1 8. Preparation of potassium azobenzene- 5 -sulfonate 76 19- Preparation of potassium azobenzene- 4-sulfonate......................... 77 20. Preparation of azobenzene-5-carboxyllc acid................................ 77 21. Preparation of potassium azobenzene- 4-carboxylate....................... 78 22. Preparation of 5-phenylazoacetophenone 78 2 5 . Preparation of 4-phenylazoaoetophenone 79 C. Preparation of els Isomers........... 00 D. Measurement of the Rate of Isomerization... 84 E. Calculation of Rate Constants........ 84 P. Calculation of the Activation Energies and Frequency Factors......................... 86 V. SUMMARY......................................... 87 APPENDIX........................................... 90 AUTOBIOGRAPHY....................................... 195 vl LIST OP TABLES Page I Synthesis of Substituted Azobenzenes..... l8 II Molecular Extinction Coefficients for Maximum Absorption for Various Azobenzenes........................... 2? III Rates of Isomerization of Substituted cis Azobenzenes....................... 34 IV Activation Energies and Frequency ' Factors for Substituted Azobenzenes.... 39 V Melting Points of cis and trans Isomers of Substituted Azobenzenes....,....... 88 VI Isomerization of 3-Cyanoazobenzene in Ethanol.............................. 121 VII Isomerization of 3-Cyanoazobenzene in Dioxane............................... 122 VIII Isomerization of 3-Cyanoazobenzene in Benzene............................... 123 IX Isomerization of 3-Cyanoazobenzene in Heptane............................... 124 X Isomerization of 4-Cyanoazobenzene in . 95 per cent Ethanol.................. 125 XI Isomerization of 4-Cyanoazobenzene in . Absolute Ethanol..................... 125 XII Isomerization of 4-Cyanoazobenzene in Dioxane............................... 127 XIII Isomerization of 4-Cyanoazobenzene in Benzene ......................... 128 XIV Isomerization of 4-Cyanoazobenzene in Heptane............................... 130 XV Isomerization of 3-Fluoroazobenzene in . Ethanol.............................. 132 XVI Isomerization of 3-Fluoroazobenzene in Dioxane............................... 153 vll Page XVII Isomerization of 5-Pluoroazobenzene In Benzene............................... 154 XVIII Isomerization of 5-Fluoroazobenzene in Heptane............................... 155 XIX Isomerization of 4-Pluoroazobenzene in Ethanol............................... 156 XX Isomerization of 4-Pluoroazobenzene in . Dioxane............................... 157 XXI Isomerization of 4-Pluoroazobenzene in . Benzene............................... 159 XXII Isomerization of 4-Pluoroazobenzene in Heptane............................... 140 XXIII Isomerization of 5-Chloroazobenzene in Ethanol............................... 142 XXIV Isomerization of 5-Chloroazobenzene in . Dioxane............................... 145 XXV Isomerization of 5-Chloroazobenzene in . Benzene............................... 144 XXVI Isomerization of 5-Ghloroazobenzene in , Heptane............................... 145 XXVII Isomerization of 4-Chloroazobenzene in Ethanol................................ 146 XXVIII Isomerization of 4-Chloroazobenzene in Dioxane................................ 147 XXIX Isomerization of 4-Chloroazobenzene in . Benzene............................... 149 XXX Isomerization of 4-Chloroazobenzene in . Heptane............................... 150 XXXI Isomerization of 5-Bromoazobenzene in Ethanol . ■ 151 viii Page XXXII Isomerization of 3-Bromoazobenzene in Dioxane............................... 152 XXXIII Isomerization of 5-Bromoazobenzene in Benzene............ 155 XXXIV Isomerization of 5-Bromoazobenzene in Heptane............................... 154 XXXV Isomerization of 4-Bromoazobenzene in Ethanol............................... 155 XXXVI Isomerization of 4-Bromoazobenzene in Dioxane............................... 156 XXXVII Isomerization of 4-Bromoazobenzene in Benzene............................... 158 XXXVIII Isomerization of 4-Bromoazobenzene in Heptane............................... 159 XXXIX Isomerization of 5-Iodoazobenzene in Ethanol............................... l6l XL Isomerization of 5-Iodoazobenzene in Dioxane............................... 162 XLI Isomerization of 5-Iodoazobenzene in Benzene............................... I65 XLII Isomerization of 5-Iodoazobenzene in Heptane............................... 164 XLIII Isomerization of 4-Iodoazobenzene in Ethanol............................... 165 XLIV Isomerization of 4-Iodoazobenzene in Dioxane............................... I66 XLV Isomerization of 4-Iodoazobenzene in Benzene.................. 168 XLVI Isomerization of 4-Iodoazobenzene in Heptane......................... I69 XLVII Isomerization of 5-Methoxyazobenzene in Ethanol............................... I7I ix Page XLVIII Isomerization of 5-Methoxyazobenzene in Dioxane............................... 172 XLIX Isomerization of 5-Methoxyazobenzene in Benzene............................... I?p L Isomerization of 5-Methoxyazobenzene in . Heptane............................... 174- LI Isomerization of 4-Methoxyazobenzene in Ethanol. .......................... 175 LIX Isomerization of 4-Methoxyazobenzene in Dioxane............................... 176 LIII Isomerization of 4—Methoxyazobenzene in Benzene............................... 178 LIV Isomerization of 4-Methoxyazobenzene in Heptane............................... 179 LV Isomerization of 5-Nitroazobenzene in Ethanol............................... l8o LVI Isomerization of 5-Nitroazobenzene in Dioxane............................... I8l LVII Isomerization of 4—Nitroazobenzene in Ethanol............................... 182
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