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 + HO₂ → [complex of reactants] → transition state → [complex of products] → product + 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.