THE OXIDATION OF PHENYLPROP-l-ENES USING MERCURY (II) CHLORIDE BY GEORGE THUKU THIONG'O A thesis submitted in part fulfilment for the Degree of Master of Science in the University of Nairobi 1937 a H V ¥ H H HOHtVfi 4 0 JU.ISHBAINQ *'U1 a Tunsi* Ri(< Trip, DRq BP.p, qu, (i i )• /''CCH,' ™ D p 0 e A c o p y V .!T.. ‘RSlTy , A? ^ACElj ifc*.... LlJ3&ABY4 This thesis is my original work and has not been presented for a degree in any other University. George Thuku Thiong'o This thesis has been submitted for examination with our approval as University supervisors. Professor K.L. Ormand Professor R.M. Hunavu Chemistry Department Chemistry Department Kenyatta University University of Nairobi (iii) Dedication To my wife, Njeri Thuku, to our son Thiong'o Thuku and to my mother Wangari Thiong'o. (iv) ACKNOWLEDGEMENTS I wish to express my sincere thanks to Professor Ormand for suggesting the research project, his encouragement, advice and support during the experimental and writing up of the thesis. I am also happy to acknowledge Professor Munavu for reading the whole thesis and offering valuable help in its organisation. Special thanks are due to Kenyatta University for partly funding this project through a research grant, the British Council for their generous gifts of samples and to Dr. Ogur and Mr. Said for analysing my samples with (n.m.r.) spectrophotometer. Thanks also are due to both teaching and technical staff of Chemistry Departments of both Kenyatta and Nairobi Universities. I am also most grateful to Miss Ann Munge for her patient and excellent work in typing the manuscript. (v) TABLE OF CONTENTS PAGE List of Tables ................................... (x) List of abbreviations ........................... (xi) Abstract ...........................................(xii) CHAPTER ONE 1.0 Previous work in the field ................ 1 1.1 Oxidation states of mercury ............ 4 1.2 Organic chemistry of mercury (II) ......... 5 1.3.0 General formation of o-bonded Organomercurials .......................... 7 1.3.1 Transmetallation .................. 8 1.3.2 Mercuration ........................ 9 1.3.3 Decomposition of mercury carboxylates, sulphonates and sulphinates ........ 13 1.3.4 Electrochemical synthesis .......... 13 1.3.5 Diazonium salts ...................... 15 1.3.6 Aromatizational mercuration ........ 16 1.3.7 Insertion of Carbenes CR2, into mercury - halogen bonds ............ 16 1.4 Reactions of mercury - carbon bond ........ 17 1.4.1 Oxymercuration - Demercuration of alkenes and other related reactions . 20 1.4.1.1 The mechanism of oxymercuration ... 22 1.4.1.2 The kinetics of Oxymercuration ... 26 1.4.3 Transmetallation .................... 35 1.4.4 Carbene transfer reactions ......... 37 1.4.5 Thermolysis and photolysis of Organomercurials .................... 41 (Vi) 1.4.6 Photolysis of “-diazoalkyl- mercurials ........................ 43 1.4.7 Reaction with proton acids ....... 43 1.4.8 Reduction ......................... 4 7 1.4.9 Oxidation by Oxygen ............... 49 1.4.10 Oxidation by mercury (II) salts ... 54 1.4.11 Autooxidation ..................... 56 1.4.12 Allylic Oxidation ................. 58 1.4.13 Carbonylation ..................... 60 1.4.14 Oxidation by other metals ........ 63 1.5 Objectives of this study .................. 68 CHAPTER TWO RESULTS AND DISCUSSION 2.1 Synthesis ................................. 70 2.1.1 Synthesis of 3,4-methylene- dioxyphenylprop-l-ene (isosafrole) . 74 2.1.2 Attempts to obtain 3,4-methylenedioxy- phenylprop-l-ene ................. 80 2.1.3 Attempted synthesis of 3,4-methylene- dioxyphenylprop-l-ene ............. 80 2.1.4 Attempted isomerisation of 3.4- methylenedioxyphenylprop-2-ene (safrole) .......................... 85 2.1.5 Attempted hydrochlorination of 3.4- methylenedioxyphenylprop-2-ene . 90 2.2 Oxidation of phenylprop-l-enes ........... 91 2.2.0 Oxidation of 4-methoxyphenyiprop-l- ene ................................ 91 2.2.1 Oxidation of other phenylprop-i- enes ............................... 95 2.3 Attempted studies on mechanism of oxidation of phenylprop-l-enes ..................... 105 2.3.0 Rise of mercury in capillary tubing experiment ................. 105 < (vii) 2.3.1 N.M.R studies .................... 108 2.3.2 U.V. studies ..................... 116 CHAPTER THREE EXPERIMENTAL 3.0 General experimental ...................... 123 3.1 Synthesis of 3,4-methylenedioxypher.yl- prop-l-ene and other required compounds .. 123 3.1.0 Extraction of 4-methoxyphenyl- prop-l-ene ........................ 124 3.1.2 Dehydration of phenylpropan-l-ol ••• 124 3.1.3 Methylation of 4-hydroxy-3-methoxy- phenylprop-l-ene .................. 125 3.1.4 Preparation of 3,4-methylene- dioxyphenylpropan-l-ol ............ 127 3.1.5 Dehydration of 3,4-methylene- dioxyphenylpropan-l-ol ............ 128 3.1.6 Synthesis of methylenedioxy- benzene ....................... •. .. 129 3.1.7 Purification of benzoyl chloride .. 131 3.1.8 Preparation of propanoyl chloride .. 131 3.1.9 Attempted preparation of 3.4- methylenedioxyphenylpropan-l- one ................................ 132 3.1.10 Attempted reduction of the crude acylated methylenedioxybenzene .... 133 3.1.11 Attempted dehydration of the crude oil produced by reduction of crude acylated methylenedioxybenzene • •••« 134 3.1.12 Attempted preparation of 3.4- methylenedioxyphenylpropan-l-one using Aluminium chloride ........... 134 3.1.13-14 Attempted dehydration of 3,4-methylenedioxyphenylpropan-l- ol .............................. 135 (viii) 3.2 Attempted isomerisation of 3,4-methylenedioxy- pheny lprop-2-ene (saf role) .................... 136 3.2.0 Isomerisation in presence of potassium hydroxide .................. 136 3.2.1 Isomerisation in presence of potassium hydroxide followed by fractional distillation .............. 138 3.2.2-3 Isomerisation in presence of alcoholic potassium hydroxide ..... 139 3.2.4 Isomerisation under acidic conditions ............................ 141 3.2.5 Isomerisation using sunlight ........ 141 3.3 Attempted hydrochlorination of 3,4-methylene- dioxyphenylprop-2-ene ........................ 142 3.3 Hydrochlorination as neat .............. 14 2 3.3.1 Hydrochlorination in tetrachloro- methane ................................ 142 3.3.2 Hydrochlorination in dichloromethane .. 143 3.3.3 Hydrochlorination in nitromethane .... 143 3.4 Studies on oxidation of phenylprop-1-enes using mercury (II) chloride ................. 144 3.4.1 Oxidation of 4-methoxyphenvlprop-l- ene in diethyl ether - water mixture .............................. 144 3.4.2 Oxidation of 4-methoxyphenylprop-l- ene in dimethyl sulphoxide - water mixture ............................... 146 3.4.3 Oxidation of 4-methoxyphenylprop-l- ene in presence of oxygen gas ....... 149 3.4.5-7 Oxidation of 4-methoxyphenylprop-l- . ene in ethanol - water mixture ..... 149 3.4.8 Oxidation of 4-methoxyphenylprop-1- ene in absolute ethanol (for deter­ mining yield) ......................... 152 3.4.9 Preparation of 4-methoxybenzaldehyde mercury (II) chloride complex ....... 153 3.4.10 Oxidation of 3,4-dimethoxypheny lprop-1 - ene in diethyl ether - water mixture .. 154 3.4.11 Oxidation of 3,4-dimethoxypheny lprop-1- ene using potassium permanganete .... 155 (ix) 3.4.12 Oxidation of phenylprop-l-ene in diethyl ether - water mixture .... 156 3.4.13 Oxidation of 3,4-methylenedioxy- phenylprop-l-ene in absolute ethanol ........................... 158 3.4.14 Preparation of 3,4-methylene- dioxyphenylbenzaldehyde mercury (II) chloride complex .................. 159 3.4.15 Oxidation of crude 3,4-methylene- dioxyphenylprop-l-ene in absolute ethanol ............................ 159 3.4.16 Oxidation of 4-hydroxy-3-methoxy- phenylprop-l-ene in diethyl ether - water mixture ................... 160 3.4.17 Oxidation of 3,4-irethylenedioxy- phenylprop-2-ene (safrole) ...... 163 3.5 Mechanistic studies ...................... 164 3.5.1 Oxidation of 4-methoxyphenyl- prop-l-ene under controlled conditions ........................ 164 3.5.2 NMR studies on the reaction of some phenylprop-l-enes with mercury (II) chloride .......................... 167 3.5.2.1 Attempted calibration using diethyl ether as solvent .. 167 3.5.2.2 Repeated calibration using dimethyl sulphoxide ...... 169 3.5.2.3 An attempt to follow the mechanism of the reaction of some phenylprop-l-enes with mercury (II) chloride . 171 3.5.3 Mechanistic studies using U.V. spectrophotometry ........ ......... 173 References ........................................ 181 (X) LIST OF TABLES TABLES PAGE 1 Extinction coefficients for 4-methoxy- benzaldehyde and 4-methoxyphenylprop-l- ene at 273 nm. and 259 n m ................... 117 2 Changes in refractive index with time for isomerised 3,4-methylenedioxyphenyl- prop-2-ene (safrole) mixture .............. 137 3 Changes in refractive index for portions obtained by fractional distillation of isomerised safrole mixture ................ 138 4 Changes in refractive index with time for isomerised safrole mixture ............ 139 5 Rise of mercury in capillary with time .... 165 6 Attempted n.m.r. calibration using diethyl ether as solvent ........................... 168 7 NMR calibration using d, dimethyl sulphoxide as solvent ...................... 170 8 Ultraviolet calibration for phenylprop-1- ene oxidation using mercury (II) chloride .. 174 9 Ultraviolet spectral data for mixture number 1 175 10 Ultraviolet spectral data for mixture number 2 177 11 Ultraviolet spectral data for mixtures 3 to 7 and their calculated concentrations 180 (xi) LIST OF ABBREVIATIONS 1. DMF