Microcanonical modeling of the thermokinetic method.

A microcanonical analysis of the thermokinetic method is performed using statistical rate calculations based on orbiting transition state theory in order to model a proton transfer process: MH(+) + B(i) --> M + B(i)H(+). The reaction efficiency is calculated as a function of the difference in zero point energy of reactants and products. Several models of reactions were investigated in order to simulate situations where the base of interest M exhibits loss of entropy upon protonation of up to approximately 40 J mol(-1) K(-1). It is shown that the standard thermokinetic method would predict correct 298 K gas phase basicities, GB(298)(M), even for polydentate molecules M, if experiments are conducted at this temperature. Proton affinity, PA(298)(M), and protonation entropy may be obtained by the thermokinetic method only in special circumstances such as, for example, experiments conducted at various temperatures.