A theoretical study of solvent effects on the relative thermodynamic stabilities of the allyl+/F- and allyl-/Li+ ion pairs in polar media

Abstract

The relative thermodynamic stabilities of several ion-pair structures, including intimate and solvent-separated forms, in solution have been studied for the allyl+/F- and allyl-/Li+ model systems. The electrostatic part of the solvent effects was modelled through the self-consistent reaction field ( SCRF ) theory and an extension of it including desolvation effects ( SCRF/D theory ). Specific solvent effects were also analysed by explicitly incorporating a solvent molecule, via the supermolecule (SM) approach. It is shown that a more complete thermodynamic description of these systems is attained by using mixed continuum-SM schemes. This last approach allows qualitative separation of the individual contributions of the electrostatic and hydrogen-bonding effects, which are particularly relevant to a discussion of the relative stabilities of intimate and solvent-separated ion pairs in these systems. © 1990.