Arrhenius activation energy of reactions that are almost diffusion-controlled

Abstract

Expressions are derived for the Arrhenius activation energy (E_a) of bimolecular reactions in solution occurring on almost every collision, in terms of the parameter B from the temperature-dependence of the solvent viscosity. Applied to a single reaction occurring with constant parameters of reaction in solutions of variable viscosity and variable values of B, it is deduced that over these various solvents, E_a should be a linear function of B, with an intercept approximating to RT, regardless of the magnitude of the (small, constant) critical energy requirement, E^* of the reaction. This conclusion negates a recent assertion that the intercept is a measure of E^*.