The Determination of Absolute Rate Constants in Olefinic Oxidations

L. Bateman, G. Gee
1948 Proceedings of the Royal Society A  
On the basis of the reaction mechanism established in the preceding paper (this volume, p. 376), the changes in rate of photo-oxidation observed in intermittent light when a rate contribution is made by a simultaneous dark reaction have been rigorously analyzed. Using this analysis and the relevant experimental data, the velocity coefficients of the rate con trolling propagation and termination reactions have been separately evaluated for cyclohexene, 1-methylcycfohexene, dihydromyrcene and
more » ... ydromyrcene and ethyl linoleate. The significance of the results in interpreting the finer details of the oxidation mechanism is discussed; and the numerical values are compared with similar data reported for polymerization systems. A criterion for detecting anomalous effects due to intense light absorption is derived; further to the evidence presented in the preceding paper, ethyl linoleate undergoing oxidation in light of wave-length 2537 A is found to exemplify this behaviour. I n t r o d u c t io n In the preceding paper, a kinetic analysis has shown th at the photo-oxidation of certain olefins proceeds by a radical chain mechanism similar in all but the initiation process to th at established by Bolland for the analogous thermal reactions. The observed overall rate of oxidation, except a t low oxygen pressures, is determined by the rates of three elementary steps: (а) The rate ri at which free radicals are produced in the initiation stage (б) The rate at which peroxide radicals R 0 2-react with the olefin I?H (velocity constant &3). (c) The rate of mutual destruction of R0 2-rad The overall rate r is given by r = k2Jc6 *[-RH]rk (1)
doi:10.1098/rspa.1948.0126 fatcat:u7k4ipy7c5esrdxok3vy3s4mxe