THE ORIGIN OF LEAVING-GROUP EFFECTS IN RADICAL REACTIONS TRIGGERED BY SOLVATED ELECTRON REDUCTION

Reactions between solvated electrons and substrates yielding fast-cleaving anion radicals or giving rise to concerted bond cleavage occur during the mixing of the two reactants. They are described by a model allowing the quantitative prediction of product distribution in which the initial and successive chemical steps take place in a thin reaction layer located within the diffusion layer where the two reactants mix. The essential cause of the observed leaving-group effects resides in the decrease of the amount of electrons in thc reaction layer as the initiating reaction becomes faster and faster. In the case of S(RN)1 substitutions, an additional factor is the parallel acceleration of the electron transfer between the substituted anion radical and thc substrate.