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Ab initio study of the CH <inf>3</inf>O <inf>2</inf> self-reaction in gas phase: Elucidation of the CH <inf>3</inf>O <inf>2</inf> + CH <inf>3</inf>O <inf>2</inf> → 2CH <inf>3</inf>O + O <inf>2</inf> pathway

Abstract:

Ab initio electronic structure calculations have been performed to determine the mechanism governing the 2CH 3O 2 → 2CH 3O + O 2 chemical reaction in gas phase. Geometry optimizations for reactants, intermediates, transition states, and products were performed at the MP2 level of theory with the 6-311G(2d,2p) basis sets. Further, PMP4(SDTQ)/6-311G(3df/,2p) single-point calculations were performed on the previous MP2/6-311G(2d,2p)-optimized geometries, For the past 50 years, it has been proposed that the production of CH 3O and O 2 in the self-reaction of methylperoxyl radicals is the result of the direct dissociation of a noncyclic tetraoxide intermediate via a concerted mechanism involving a single step. Our theoretical results indicate that the reaction path is more complex than expected. We found that the reaction proceeds through a nonconcerted mechanism involving two tetraoxide intermediates that have different geometries and relative energies. © 2003 Wiley Periodicals, Inc.