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

Abstract

The values of density, ρ 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, η 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, Vϕ, limiting apparent molar volume, Vϕ° and the slope, Sv, transfer volume, Vϕ,tr°, apparent molar compressibility, Ks,ϕ, limiting apparent molar compressibility, Ks,ϕ° and the slope, Sk, transfer volume, Vϕ,tr°, transfer compressibility, Ks,ϕ,tr°, limiting apparent molar expansivity, Eϕ°, Hepler’s constant, (∂2Vϕ°/dT2), 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, Δμ1°# and per mole of solute, Δμ2°#, entropies, ΔS° and enthalpies, ΔH° 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 (∂2Vϕ°/dT2) and dB/dT. The results have been interpreted in terms of solute–solvent and solute–solute interactions in these systems.