Solvent effects on chemical processes. V: Hydrophobic and solvation effects on the solubilities of substituted biphenyls in methanol/water mixtures.

A phenomenological model that permits solvent effects to be separated into general medium effects (the solvophobic effect) and solvation effects is applied to the solubility of a series of biphenyl compounds in methanol/water mixtures. The parameters of the model (gA, K1, and K2, K1 and K2 are equilibrium constants for solvation and gA describes the general medium contribution) were evaluated from the nonlinear regression of the model equation to the data. It was found that the surface tension curvature factor (g) was 0.37, that A represents the hydrophobic (nonpolar) surface area of the solute molecule, and that K1 and K2 were 2.53 and 1.77 (means for solutes in methanol/water), respectively. These results permit solvent effects on solubility in methanol/water to be predicted and they refine the interpretation of the solvent effect model.