Rate Constants for Hydrogen Abstraction Reactions by the Hydroperoxyl Radical from Methanol, Ethenol, Acetaldehyde, Toluene, and Phenol

An important step in the initial oxidation of hydrocarbons at low to intermediate temperatures is the abstraction of H by hydroperoxyl radical (HO2). In this study, we calculate energy profiles for the sequence: reactant 1 HO2 + [complex of reactants] -> transition state -> [complex of products] -> product 1 H2O2 for methanol, ethenol (i.e., C2H3OH), acetaldehyde, toluene, and phenol. Rate constants are provided in the simple Arrhenius form. Reasonable agreement was obtained with the limited literature data available for acetaldehyde and toluene. Addition of HO2 to the various distinct sites in phenol is investigated. Direct abstraction of the hydroxyl H was found to dominate over HO2 addition to the ring. The results presented herein should be useful in modeling the lower temperature oxidation of the five compounds considered, especially at low temperature where the HO2 is expected to exist at reactive levels. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 1725-1733, 2011