Self-Termination and Electronic Spectra of Substituted Benzyl Radicals in Solution

Article abstract of DOI:10.1021/j100234a026

Several substituted benzyl radicals have been generated in liquid cyclohexane by the photolysis of symmetrically substituted dibenzyl ketones.The rate constants for self-termination to substituted bibenzyls, and absorption spectra of the transient radicals, have been measured by optical modulation spectroscopy.The termination rates are generally well described by the von Smoluchowski equation with a spin factor of 1/4.Deviations are discussed in terms of steric retardation and the unreliability of the estimated reaction diameters of radicals with bulky substituent groups.Absorption spectra of the three monomethyl-, the three monochloro-, two dichloro-, and the three monomethoxybenzyl radicals demonstrate the influence of the substituents on the energy levels of the benzyl system.