STUDIES ON THE DISSOCIATION-CONSTANTS AND SOLUBILITIES OF AMINO-ACIDSIN ETHYLENE-GLYCOL PLUS WATER MIXTURES

The dissociation constant and solubility of a number of amino acids ha ve been determined PH-metrically and spectrophotometrically in ethylen e glycol (EG) + water mixtures at 298 K. The free energies of transfer of amino acids from water to mixed solvents, thus obtained, have been coupled with the free energies of transfer [Delta G(t)(o) (1) and Del ta G(t)(o) (2)] for the reactions RH(2)(+) + H2O reversible arrow RH() + H3O .... (1) and RH(+) + H2O + R(-) + H3O+ .... (2) and Delta G(t) (o)(H+) values determined in our laboratory to get the Free energies o f transfer of RH(2)(+) and R(-) in different mixed solvents. These giv e the quantitative measures of ion-solvent interactions of the zwitter ions, cations and anions of the amino acids. The results have been dis cussed in terms of structural changes of solvent mixtures resulting in the change in acid-base properties and solute-solvent interactions. A critical assessment has been made regarding the determination of sing le ion values.