Three-Dimensional Case in Solvation Thermodynamics: Variation of Temperature, Transfer Route, and Thermodynamic Function

In this work, we considered a complex case in solvation thermodynamics, referred to as the ‘three-dimensional solvation’ where the three ‘dimensions’ are being varied, viz., (1) the solute transfer is described between three phases (gas-to-liquid, gas-to-water, and liquid-to-water), (2) the transfer is accomplished in a wide temperature range at constant pressure, and (3) the solvation thermodynamics is given by four thermodynamic functions, Δ X = (Δ G, Δ H, Δ S, Δ C P ). The analysis has been performed within the framework of the Correlated States Theory of hydrophobic effect ( J. Phys. Chem. B, 2025, 129 (21), 5245–5267), which introduces the new physical entity, i.e., the correlated/uncorrelated state of solute–water pair, enabling us to fully quantify the g → w hydration thermodynamics. It was shown that the ‘three-dimensional’ solvation task is completely solvable if the concept of correlated pairs is transferred to the g → l route. Interrelations between the heat capacity changes and enthalpy/entropy convergence temperatures for different transfer routes, known previously from empirical thermodynamic studies, have been derived as a general consequence of solvation theory.