Thermodynamics of transfer of electrolytes and ions from water to aqueous solutions of polyhydroxy compounds

Abstract

The free energies, entropies and enthalpies of transfer of tetraphenylarsonium benzoate (Ph₄AsBz), tetraphenylarsonium picrate (Ph₄AsPi), potassium tetraphenylboride (KPh₄B), silver picrate (AgPi) and potassium picrate (KPi) from water to aqueous solutions of mannitol, sorbitol and sucrose have been determined from solubility product (K_sp) measurements of these salts at different temperatures. The transfer values for the constituting ions have been evaluated using the TATB assumption. Values of ΔG⁰_t for the cations and anions of these salts indicate that these ions are destabilized in these media. ΔS⁰_t and ΔH⁰_t for the ions indicate that these polyhydroxy compounds break the water structure and structure breaking ability follows the sequence sucrose > sorbitol > mannitol. The results have been explained in terms of the overlap cospheres model of solute/ion hydration.