Ab initio study of the CH3O2 self‐reaction in gas phase: Elucidation of the CH3O2 CH3O2 → 2CH3O O2 pathway

Abstract Ab initio electronic structure calculations have been performed to determine the mechanism governing the 2CH3O2 → 2CH3O + O2 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 CH3O and O2 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. Int J Quantum Chem, 2004