Chemical Kinetics

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Text extracted from opening pages of book: THE GEORGE FISHER BAKER NON-RESIDENT LECTURESHIP IN CHEMISTRY AT CORNELL UNIVERSITY Chemical Kinetics BY FARRINGTON Professor of Chemistry in the University of Wisconsin ITHACA NEW YORK CORNELL UNIVERSITY PRESS LONDON: HUMPHREY MILFORD OXFORD UNIVERSITY PRESS 1938 COPYRIGHT 1938 BY CORNELL UNIVERSITY PRINTFD IN THE UNITED STATES OF AMERICA Qtt) t < Eiill* giatr fJreaa C. EORC. E BANTA PXTBMSHING COMPANY, MFNASHA, WISCONSIN PREFACE THIS book is based on lectures delivered at Cornell University under the George Fisher Baker Non-Resident Lectureship in Chemistry from February to June 1935. So rapidly is our under standing of Chemical Kinetics changing that it has been necessary to include additional material up to the time of the completion of the manuscript in 1937. I appreciate the opportunity accorded me by the George Fisher Baker Fund. This lectureship, established a decade ago, has en-, abled Cornell to do much for Chemistry in America. It has brought the stimulus of foreign chemists to us and it is now leading in a much needed visitation of professors among our own universities. Wisconsin University and Cornell University have much in com mon. I am glad to have had the privilege of telling each about the other. Particularly I wish to thank Professor J. Papish and all the members of the chemistry department for their cordial hospitality during our pleasant visit in Ithaca. FAKRINGTON DANIELS Madison, Wisconsin, October, 1936. CONTENTS I. INTRODUCTION 1 II. GENERAL PRINCIPLES .... 8 Order of reaction ........ . . . 8 Specific reaction rate. . . 14 Chemical equilibrium. . . . 15 The Arrhenms equation 18 The kinetic theory of gases . . . . 24 Complicated reactions . ... . 27 III. THEORIES OF UNIMOLECULAR REACTIONS. ... . . 31 The radiation hypothesis . . 31 The collision hypothesis . 37 Chain reactions . 44 Free radicals 49 IV. GAS PHASE REACTIONS 56 Experimental technique ... 57 The decomposition of nitrogen pentoxide 60 The decomposition of ethyl bromide 72 Literature 86 V. CHEMICAL KINETICS OF REACTIONS IN SOLUTION. ... 90 Collision frequency , 91 Comparison between reactions in gas and in solution ... . . . . 93 Solvation 96 The decomposition of nitrogen pentoxide 100 The decomposition of chloroacetate ion 107 Ionic reactions ... 110 The decomposition of ammonium amalgam . 114 VI. PHOTOCHEMISTRY 117 Photochemical principles 118 Absorption of radiation 120 Photochemical kinetics 124 Experimental technique 127 Quantum yield 135 The photolysis of nitrogen oxides: N 2 O 6 , N 2 O4 and NOa 137 The photolysis of acetone 147 The photobrqmination of cinnamic acid 157 The photolysis of beta-caryophyllene nitrosite 167 The formation of vitamin D 169 Photosynthesis by chlorophyll 172 Literature 176 VII. ELECTRICAL ACTIVATION 181 Electrical discharges in gases 182 Chemical reactions in electrical discharges 185 Chemical effects of alpha particles 188 Chemical effects of cathode rays 191 Chemical effects of X-rays 195 Chemical effects of low voltage electrons 198 VIII. INFRARED SPECTROSCOPY 201 Experimental technique 202 viii CHEMICAL KINETICS Ethyl bromide 204 Acetic acid. . . . . . ... .214 Theoretical considerations . 216 IX. THEORETICAL CALCULATION OF ACTIVATION ENERGIES. ... . 220 Energy and interatomic distance 222 The semi-empirical method. The bromination of ethylene. . . 227 Chemical applications 234 The statistical mechanical method .... 239 X. I SOTOPIC TRACERS . 244 Isotopic carbon. . . 245 Literature 257 INDEX 263 CHAPTER I INTRODUCTION ACCORDING to the announcement of the Department of Chemistry of Cornell University, I am to present the most recent advance ments and the results of my own investigations in the field. I shall try to do this in chemical kinetics, and, in describing my researches and those of others, I shall try to illustrate current theories and to give glimpses of present frontiers. It is my hope that interest in the subject will not be confined to physical chemist