Gas-phase reaction of the OH-benzene adduct with O2: reversibility and secondary formation of HO2

The reaction of OH radicals with benzene and consecutive reactions of benzene-OH adducts with O2 were studied in the gas phase in N2-O2 mixtures at atmospheric pressure and room temperature. OH was produced by pulsed 248 nm photolysis of H2O2. Time-resolved detection of both OH and benzene-OH adducts was performed by continuous-wave (cw) UV-laser long-path absorption at around 308 nm. The reaction: OH + benzene -> products [reaction (1)] was not affected by the presence of O2. Rate constants k1= (1.10 +/- 0.07) x 10-12 cm3 s-1 and (1.06 +/-0.07) x 10-12 cm3 s-1 were obtained in N2 and O2, respectively. In N2 addition of NO2 did not change k1, from which an upper limit of 5% is derived for formation of H atoms in reaction.