Study of the Gas-Phase Oxygen-Hydrogen Exchange Reaction of O(P-3) + i-C3H7 -> H(S-2) + CH3COCH3

Abstract

The gas-phase oxygen-hydrogen exchange reaction dynamics of O(P-3) + i-C3H7 (isopropyl) -> H(S-2) + CH3OCH3 (acetone) was first investigated by the vacuum-ultraviolet laser-induced fluorescence (VUV-LIF) spectroscopy in a crossed beam configuration. The nascent H-atom Doppler-profile analysis shows that the average translation energy of the products and the fraction of the total available energy released as the transitional energy were determined to be 33.3 +/- 1.64 kcal mo1(-1) and 0.38, respectively. With the aid of the CBS-QB3 level of ab initio theory and statistical calculations, it was found that the title reaction is one of the major reaction pathways and proceeds through the formation of dynamical, short-lived addition complexes. On the basis of a systematic comparison with several exchange reactions of hydrocarbon radicals, the large variation in the fractions of translational energy release can be understood in terms of the unique geometrical features of the transition states along the reaction coordinates on the doublet potential energy surfaces.