Theoretical studies of unimolecular reactions of C2–C5 alkoxy radicals. Part II. RRKM dynamical calculations

Abstract

Rate constants for the unimolecular decomposition and isomerisation reactions of primary and secondary alkoxy radicals up to pentoxy have been determined theoretically. We make use of a formerly derived extensive set of ab initio data to calculate specific rate constants via RRKM theory. A subsequent master equation analysis provides a weak collision treatment with inclusion of multi-channel fall-off effects. The resulting kinetic data are compared with rate constants reported in the literature. Good agreement was found with the more established experimental values, which confirms our modified G2(PMP2,SVP) approach to yield critical barriers of chemical accuracy. In addition, we provide an analytical parameterisation of our theoretical fall-off curves in terms of the semi-empirical Troe-formalism, which can easily be used for purposes of atmospheric modelling. Furthermore, our results represent a complete set of kinetic data, which allow a systematic comparison of the reactivity of different alkoxy radicals.