Central-force models for proton-transfer reactions

Abstract

A general central-force model is used to calculate free-energy changes and Brönsted exponents for proton-transfer reactions. The exponents assume different values for the separate variations of the acidic and basic reactants, the value being always greater for the former type of variation, and a symmetrical transition state does not correspond to an exponent equal to one-half. The results cast some doubt on the procedure commonly adopted for using the curvature of Brönsted plots to deduce the energy of solvent reorganisation in the transition state.