Pressure dependence of activation and reaction volumes

Abstract

A simple theoretical model of high-pressure kinetic effects is proposed based on the assumption that characteristic (initial, transition or product) states of a reacting system should be identified with stationary points of an enthalpy surface rather than those of a regular potential-energy surface (p.e.s.). An explicit treatment of the deformation of a p.e.s. promoted by pressure enables one to improve the simple cylinder Stearn–Eyring model of activation volumes so as to describe the pressure dependence of activation and reaction volumes. The dependence thus obtained agrees well with experimental data in the wide pressure range from 0 to 45 kbar. The pressure behaviour of activation enthalpies and entropies is also discussed.