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 (Ph,AsBz), tetraphenylarsonium picrate (Ph,AsPi), potassium tetraphenylboride (KPh,B), silver picrate (AgPi) and potassium picrate (KPi) from water to aqueous solutions of mannitol, sorbitol and sucrose have been determined from solubility product (KJ measurements of these salts at different temperatures. The transfer values for the constituting ions have been evaluated using the TATB assumption. Values of AG: for the cations and anions of these salts indicate that these ions are destabilized in these media. AS: and AH: 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.

Partial molar heat capacities and volumes of transfer of some saccharides from water to aqueous urea solutions atT= 298.15 K

“…The hydration characteristics of saccharides (1)(2)(3)(4)(5)(6) and their interactions with electrolytes and nonelectrolytes (7)(8)(9)(10)(11)(12)(13)(14)(15) in aqueous media are of significant biological and thermodynamic importance. It has been widely reported (16)(17)(18)(19)(20)(21)(22) that sugars and polyols act as efficient stabilizing agents for proteins/enzymes because of their ability to enhance the structure of water.…”

Activity Coefficients and Volumetric Properties for the NaBr + Maltose + Water System at 298.15 K

“…Saccharides and their derivatives play a very important role in various biological systems. In recent years, the hydration characteristics of saccharides − and their interactions with electrolytes and nonelectrolytes − in aqueous media have developed a great deal of interests, due to their significant importance in several fields such as biology, biochemistry, catalysis, and pharmaceutical industry.…”

Single-ion enthalpies and entropies of transfer from water to aqueous urea solutions at 298.15 K

“…Several authors (20,33,34) have used changes in solvent organization brought about by cosphere overlap between cosolvent and transferred ion to explain patterns observed in single-ion entropies and enthalpies of transfer.…”

“…J. Chem. Downloaded from www.nrcresearchpress.com by 34 hydration zones. In effect, the presence of urea diminishes the structure-promoting capacity of the hydrophobic ion.…”