Collect. Czech. Chem. Commun. 1998, 63, 1969-1976

On the Calculation of Transition State Activity Coefficient and Solvent Effects on Chemical Reactions

Alvaro Domínguez, Rafael Jimenez, Pilar López-Cornejo, Pilar Pérez and Francisco Sánchez

Department of Physical Chemistry, Seville University, c/Professor Garcia Gonzales s/n, 41012, Sevilla, Spain


Solvent effects, when the classical transition state theory (TST) holds, can be interpreted following the Brønsted equation. However, when calculating the activity coefficient of the transition state, γ# it is important to take into account that this coefficient is different from that of the precursor complex, γPC. The activity coefficient of the latter is, in fact, that calculated in classical treatments of salt and solvent effects. In this paper it is shown how the quotients γ#PC change when the reaction medium changes. Therefore, the conclusions taken on the basis of classical treatments may be erroneous.

Keywords: Transition states; Precursor complex; Medium effect; Reaction kinetics; Activity coefficients; Solvent effects.