ARE POSITIVE-ION RADICALS FORMED IN PULSE-RADIOLYSIS OF ALKYLBENZENESULFONATES

Oxidation of alkylbenzenesulfonates by OH radicals proceeds via two routes: 75-85% of the OH radicals react via addition to the benzene ring, while the rest abstract an H atom from the alkyl group. The relative distribution between the two paths of reaction depends on the nature of the alkyl group. No evidence for the formation of cation radicals from OH adducts was found. H radicals add to the benzene ring to form cyclohexadienyl type radicals, but when reacted with isopropylbenzenesulfonate about 15% of the H radicals abstract hydrogen from the alkyl to form the benzyl type radical. The reaction of SO4.- with alkylbenzenesulfonates produces 50-70% OH adducts and the rest are the benzyl type radicals. At high concentrations of solute and persulfate a short-lived precursor to the benzyl radicals has been observed. The precursors observed with p-toluenesulfonate, isopropylbenzenesulfonate, and m-toluenesulfonate decay in a first-order process with the rates 1.4 x 10(6), 9.4 x 10(5), and 2.5 x 10(5) s-1, respectively. The short-lived precursor is identified as an unstable OH adducts to the benzene ring.