Solvation thermodynamics and the physical–chemical meaning of the constant in Abraham solvation equations

Abraham solvation equations find widespread use in environmental chemistry. Until now, the intercept in these equations was determined by fitting experimental data. To simplify the determination of the coefficients in Abraham solvation equations, this study derives theoretical expressions for the value of the intercept for various partition processes. To that end, a modification of the description of the Ben-Naim standard state into the van der Waals volume is proposed. Differences between predicted and fitted values of the Abraham solvation equation intercept for the enthalpy of solvation, the entropy of solvation, solvent–water partitioning, air-solvent partitioning, partitioning into micelles, partitioning into lipid membranes and lipids, and chromatographic retention indices are comparable to experimental uncertainties in these values.

► Theoretical expressions are derived for the value of the intercept in Abraham solvation equations.
► A description of the Ben-Naim standard state in terms of the van der Waals volume is proposed.
► Differences between predicted and fitted values are comparable to experimental uncertainties.