Thermodynamic functions for the transfer of 1-naphthoic acid from water to mixed aqueous solvents at 298 K
Values of free energies, ΔG⊖t, enthalpies, ΔH⊖t, and entropies, ΔS⊖t, of transfer of 1-naphthoic acid from water to water + ethanol, water + t-butyl alcohol and water + dimethyl sulphoxide (DMSO) mixtures at various mole fractions have been determined from solubility measurements at different temperatures. Variations of ΔG⊖t with xcosolvent in the water-rich alcoholic mixtures are governed by the sign of the entropy term. For water + DMSO mixtures ΔG⊖t is negative, but the variation of ΔH⊖t with xDMSO shows different behaviour from that of water + alcohol mixtures. We have calculated molecular pair-interaction parameters (gxy, hxy and TSxy) in water for the three systems studied; hxy > 0 for water + alcohol mixtures and hxy < 0 for water + DMSO mixtures. The results are discussed in terms of solute–cosolvent and solute–water interactions.