Kinetics of solvolytic reactions. Dependence of composition on time and of rate parameters on temperature

Abstract

Kinetic parameters describing the solvolysis of alkyl halides in water at fixed temperature and pressure are considered in terms of both one-stage and two-stage processes. In the latter case the consequences are explored of using both the steady-state hypothesis and the fully integrated form of the rate expression. The first-order rate constant calculated from experimental data has not discriminated between these alternative descriptions. The integrated form based on a two-stage reaction is considered the correct approach. Calculations for model systems throw some doubt on the validity of the steady-state approximation for these systems. Further, the steady-state assumption leads to an underestimate of the apparent heat capacity of activation when compared with the values calculated using the fully integrated form of the rate expression.