Correlating solvation free energies and surface tensions of hydrocarbon solutes.

A simple equation relating ratios of transfer free energies and solvation free energies to surface tension is derived. When applied to hydrocarbons in water, experimental values for macroscopic surface tension yield remarkably accurate predictions of a ratio involving microscopic quantities, if one uses transfer free energies which have been adjusted for the effects of solute/solvent volume differences. The results support the validity of applying macroscopic concepts such as interfacial free energy at the molecular level. They further suggest that molecular volume as well as surface area contributes to the solubility of hydrocarbons in water.