Reactions of presolvated electrons and hydrogen atoms with benzyl chloride in methanol. A pulse radiolysis study

Abstract

On pulse radiolysis at room temperature of acidic methanolic solutions of benzyl chloride, the absorption spectrum of the benzyl radical is observed to be completely developed within 20 ns with a Gε value at 315 nm of (2.27 ± 0.04)× 104. 60Co γ-irradiation of an acid solution with [C6H5CH2Cl]= 0.36 mol dm–3 resulted in the formation of chloride ion with G(Cl–)= 4.25 ± 0.30. At temperatures between 125–213 K some absorption due to benzyl radical was observed at the end of the pulse but further absorption developed after the pulse. The spectrum of the species formed after the pulse was resolved and shown to be different from that of the benzyl radical. The species formed after the pulse is ascribed to ·C6H7CH2Cl formed by addition of H atom to the aromatic ring of benzyl chloride. Studies on the kinetics of the growth of absorption at 315 nm permitted the determination of the rate constants, k4 and k7, of reactions (4) and (7) H·+CH3OH → H2+·CH2OH (4), H·+ C6H5CH2Cl →·C6H7CH2Cl (7), and also their dependence on temperature, which conformed to the Arrhenius expression. The dependences of the yields of C6H5CH2· and ·C6H7CH2Cl on the concentration of benzyl chloride were determined and are explained by a model which involves reaction of benzyl chloride with presolvated electrons.