Studies 0n Ion Association of Some Α-Amino Acids with L-Ascorbic Acid In Aqueous Solution at Different Temperature

Abstract

Molar conductivity of ascorbic acid (AA) with some α–amino acids (glycine(Gly), methionine (Met), cysteine (Cys) and tryptophan (Trp)) in aqueous solutionwas measured at range temperatures from 298 K to 313 K. Λo. The limiting molarconductivity, KA, the association constant was calculated using the Shedlovskymethod, and R, the association distance calculated by Stokes–Einstein equation. Thethermodynamic parameters (The heat of association ΔHo, the change in Gibbs freeenergy ΔGo, the change of entropy ΔSo), and (ΔES), the activation energy were alsocalculated. All of the results obtained were discussed. The data showed theincreasing in Λo, with the increasing of temperature. The positive values for (ΔSo)and (ΔES) showed a decrease in solvation of ion–pair and signifying the highermobility of the ions. The negative value of ΔHo, refers that the association processesare exothermic. The negative values of ΔGo, are for ion association in aqueoussolution and increase with the increase in temperature.