Solvation of gaseous non-electrolytes

Abstract

Linear free energy equations, log L=c+sπ*2+aαH2+bβH2+l log L16 log L=c+sµ22+aαH2+bβH2+l log L16 have been used to analyse the solvation of a series of gaseous non-electrolytes in a given bulk solvent as log L values where L is the Ostwald solubility coefficient. The parameters π*2, αH2, βH2, log L16 and µ2 characterise the solutes and the constants c, s, a, b and l are obtained by multiple linear-regression analysis. It is shown that for solvation in the bulk solvents ethyl acetate, acetonitrile, ethanol and methanol, the contribution of hydrogen-bonding terms to solvation is quite small, the main contributing terms being an endoergic cavity term and an exoergic solute–solvent dispersion interaction term. Even with bulk water as the solvent, hydrogen-bonding interactions of the type solute (base)–water (acid) and solute (acid)–water (base) are not more than ca. -15 or -11 kJ mol–1, respectively, for DMSO (base) and ethanol (acid). It is shown also that linear free energy equations can be used for the correlation and prediction of the solubility of gaseous solutes in a given liquid phase, even when the latter is polymeric in nature.