Hydroxylated benzenes are important aromatic hydrocarbon photooxidation products. Presently very little is known about their atmospheric chemistry. FT-IR spectroscopy has been used to identify the major products of the OH-radical initiated oxidation of phenol and cresol isomers in a large volume laboratory reaction chamber in the presence of NO_x (part-per-million levels) at 298 ± 2K. The reactions have been found to produce mainly ring-retaining products consisting of (alkyl)benzenediols, (alkyl)benzoquinones and nitro(alkyl)phenols. The (alkyl)benzenediols compose the bulk of the oxidation products with molar yields > 70%. Rate coefficients for the reaction of the identified (alkyl)benzenediols and (alkyl)benzoquinones with OH radicals have also been determined using the relative kinetic technique. The aerosol formation from the OH-radical initiated oxidation of phenol and the cresols has been investigated in the laboratory reactor and also in the large outdoor EUPHORE chamber in Valencia Spain. Substantial aerosol formation was observed in all of the experimental systems and showed a dependence on the NO and H2O partial pressure in the reaction system. The product, kinetic and aerosol data is presented and reaction mechanisms leading to the observed oxidation products are proposed. Implications for the atmospheric oxidation mechanisms of aromatic hydrocarbons with respect to the classification and quantification of secondary organic aerosol (SOA) formation from aromatic hydrocarbons in the troposphere is discussed.
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