Effect of preferential solvation on reactivity of a free radical in binary solvent mixtures

Abstract

The absorption maxima of p-NH₂C₆H₄S˙ and the rate constants and relative equilibrium constants for the reversible addition reaction of p-NH₂C₆H₄S˙ with α-methylstyrene have been measured by a flash photolysis method in binary solvent mixtures with different compositions. In a polar–non-polar mixture, preferential solvation of p-NH₂C₆H₄S˙ by the polar solvent was observed via the effect on the absorption maximum and the rate parameters. The linear free-energy relationship between the reaction rate constants and the relative equilibrium constants revealed that solvation of the reactant is more important that solvation of the transition state.