Thermochemical Properties, Pathway, and Kinetic Analysis on the Reactions of Benzene with OH: An Elementary Reaction Mechanism

Kinetics for the chemical activation reaction of the OH radical with benzene and unimolecular dissociation of the adduct are analyzed using quantum Rice−Ramsperger−Kassel (QRRK) theory for k(E) and master equation analysis for pressure falloff. Thermochemical properties and reaction path parameters are determined by ab initio and density functional calculations. Molecular structures and vibration frequencies are determined at the B3LYP/6-31G(d,p) and MP2(full)/6-31G(d) levels, with single point calculations for the energy at the B3LYP/6-311++G(2df,p)//B3LYP/6-31G(d,p), composite methods of CBS-Q, CBS-QB3 and G3(MP2) and the G3 methods. The OH addition to benzene forms a chemically activated prereactive complex with a shallow well (ca. 3 kcal mol-1), which predominantly dissociates back to reactants. Additional reactions of the energized precomplex include stabilization, or forward reaction to form hydroxycyclohexadienyl radical, C•HDOH, which has a well depth of 16 kcal mol-1. This C•HDOH adduct can eithe...