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.