Linear Solvation Energy Relationships. 13. Relationship between the Hildebrand Solubility Parameter, δH, and the Solvatochromic Parameter, π*

Free energies of solution of nondipolar solutes show better linear correlation with the Hildebrand solubility parameter, δH, than with the solvatochromic parameter, π*. It is suggested that this is because the π* parameter is a better measure of dipolar solute/solvent interactions, whereas the parameter is a better measure of the interactions between solvent molecules which must be disrupted to create a cavity for the solute. Slopes and intercepts in the correlations of ∆Gs°'s of nondipolar solutes with solvent values are linear with the solute molecular volumes. The parameters appear to be sufficiently “fine tuned” that multiple parameter correlations of ∆Gs°'s of dipolar solutes with solvent π* and δH values allow (at least semiquantitative) discrimination between the solute/solvent interaction terms and the cavity terms.