Features of the potential energy surface for the reaction of HO₂ radical with acetone

Abstract

Abstract The mechanism of the reaction of acetone with HO 2 has been studied by quantum chemical computations. Different stationary points on the potential energy surface (PES) of the reaction have been characterized. These stationary points are the reactants, products, molecular complexes, and transition states. Three pathways have been studied: two H‐abstraction channels and one HO 2 ‐addition channel. The MP2 level of theory with the 6‐311G( d , p ) basis set was employed for geometry optimization. The electronic energies was obtained at the PMP2, PMP4, and CCSD(T) level of theory with the 6‐311G( d , p ) basis set on the computed geometries. The addition pathway is clearly the more favorable, contrary to the acetone + OH system. The pre‐reactive hydrogen‐bonded complexes have been characterized and show a large red shift between the OH stretching frequency in the HO 2 radical and the one in the HO 2 fragment of intermolecular complexes. Our addition rate constant k + at T = 298 K (3.49 × 10 −16 cm 3 s −1 ) is consistent with previous experimental results (giving an upper limit of the rate constant of 6 × 10 −16 cm 3 s −1 at 298 K). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007