MECHANISM AND REACTIVITY PARAMETERS OF THE REDUCTION OF ARYLMETHYL RADICALS FROM TIME-RESOLVED ELECTRON-PHOTOINJECTION EXPERIMENTS

The 9-anthrylmethyl, diphenylmethyl,benzyl, and 4-methylbenzyl radical s are generated by reduction of the corresponding chlorides with elect rons photoinjected in laser pulse experiments. The ''polarograms'' der ived from the variation of the charge flowing through the electrode wi th the de potential of the electrode represent the reduction of these radicals to the corresponding anions.: The meaning of the half-wave po tentials is investigated through their variations with the measurement time and with the addition of acids in the solution, which accelerate s the disappearance of the carbanion. Correcting the kinetic data for the effect of radical dimerization, the reduction kinetics appear to b e mostly under the control of the follow-up reaction of the carbanion with acids present in the medium, although the effect of charge-transf er kinetics begins to interfere at the lower end of the time window. T he results are compared with earlier data obtained by other techniques . The changes in reactivity observed in the series are discussed with the help of density functional quantum chemical calculations.