Laser flash photolysis study of chlorine atom/simple arene π-complexes in carbon tetrachloride and acetonitrile

Abstract

The decay kinetics of chlorine atom complexes with benzene, toluene and m-xylene were studied in carbon tetrachloride and acetonitrile solvents at room temperature. Chlorine atoms were produced by laser flash photolysis of molecular chlorine. The main reactions of the complexes were found to be the following: (i) dissociation into chlorine atom and arene with rate constants of 1 × 10 6, 5 × 10 5 and 3 × 10 5 s −1 for the benzene, toluene and m-xylene complexes respectively; (ii) isomerization to chlorocyclohexadienyl radical with rate constant of 6 × 10 4 s −1 for the benzene and toluene complexes and of less than 5 × 10 4 s −1 for the m-xylene complex; (iii) reaction with molecular chlorine with rate constants of (2–4) × 10 6 dm 3 mol −1 s −1. A method is suggested for determination of the rate constants of hydrogen atom abstractions from hydrocarbons by chlorine atoms which is based on study of the dependence on arene concentration of the decay parameter of the benzene/chlorine atom complex.