Kinetics of solvolysis of the trans-dichlorotetrapyridinecobalt(III) ion in water and in water + methanol

Abstract

Rates for the first-order solvolysis of the trans-dichlorotetrapyridinecobalt(III) ion have been measured in water and in mixtures of water and methanol for a range of temperatures. A non-linear dependence of log (rate constant) with reciprocal of dielectric constant suggests that the effects of solvent structure are important and this is confirmed by the comparison of the variation with solvent composition of the transition-state parameters with the variation with solvent composition of a range of physical properties of the solvent mixture. The application of a free-energy cycle relating the process initial state → transition state in water to that in water + methanol shows that changes in solvation of the transition state have a dominant effect on the rate.