Physicochemical study of solute-solute and solute-solvent interactions of l-phenylalanine in (water plus arabinose/glucose/sucrose) solutions at different temperatures

The values of density, rho and ultrasonic speed, u of solutions of l- phenylalanine in aqueous- carbohydrate solvents (2.5 and 5% of arabinose/glucose/sucrose, w/w in water) at T = (293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K; and viscosities, g of these solutions at (298.15, 303.15, 308.15, 313.15, and 318.15) K and at atmospheric pressure were measured. From these experimental results, the apparent molar volume, V-phi, limiting apparent molar volume, V-phi/and the slope, Sv, transfer volume, V degrees /; tr, apparent molar compressibility, Ks;/, limiting apparent molar compressibility, K (s);/and the slope, Sk, transfer volume, V degrees/; tr, transfer compressibility, K phi s;/; tr, limiting apparent molar expansivity, V degrees/, Hepler's constant, (2V(phi) /= (T2), Falkenhagen Coefficient, A, Jones- Dole coefficient, B and hydration number, nH were calculated. The Gibbs free energies of activation of viscous flow per mole of solvent, Dl # 1 and per mole of solute, Dl # 2, entropies, Delta S degrees and enthalpies, Delta H degrees of activation of viscous flow were also calculated and discussed in terms of transition state theory. The structure-making/breaking ability of the amino acid has also been discussed in terms of the sign of (2V phi/= (T2) and dB/dT. The results have been interpreted in terms of solute- solvent and solute-solute interactions in these systems. (C) 2013 Elsevier Ltd. All rights reserved.