AB-INITIO COMPUTATION OF COMBUSTION KINETICS .1. VINYL RADICAL PLUS O-2

The purpose of the work described in this paper is to investigate the utility of ab initio molecular orbital calculations for the prediction of rate constants and activation parameters of reactions occurring in hydrocarbon combustion. The reaction of vinyl radical with oxygen has been chosen because there exist reliable experimental data against wh ich the calculations can be calibrated. The results suggest that good agreement (within a factor of 2) between observed and calculated rate constants can be achieved but only ifa mechanism different from the on e previously assumed is employed. The new mechanism involves cyclizati on of the first-formed vinylperoxy radical to a three-membered-ring di oxiranylmethyl radical rather than the four-membered-ring dioxetanyl r adical that was assumed in earlier mechanisms. The agreement of the co mputed rate constants with existing experimental data, as well as the identification of the new mechanism, would appear to imply that ab ini tio calculations of the type described can have a useful role in the a nalysis of combustion processes. Predictions of results expected in sh ock-tube studies of the reaction are presented. It is shown that shock -tube experiments should provide definitive distinction between the ol d and new mechanisms for the reaction.