Volumetric, ultrasonic and viscometric studies of solute–solute and solute–solvent interactions of l-threonine in aqueous-sucrose solutions at different temperatures

Abstract

Densities, ρ of solutions of l-threonine in aqueous-sucrose solvents 5%, 10%, 15%, and 20% of sucrose, w/w in water at T=(293.15, 298.15, 303.15, 308.15, 313.15, and 318.15)K; and ultrasonic speeds, u and viscosities, η of these solutions at 298.15, 303.15, 308.15, 313.15, and 318.15K were measured at atmospheric pressure. From these experimental results, the apparent molar volume, Vϕ, limiting apparent molar volume, Vϕ∘ and the slope, Sv, 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 have been calculated. The results have been interpreted in terms of solute–solvent and solute–solute interactions in these systems. The Gibbs energies of activation of viscous flow per mole of solvent, Δμ1∘# and per mole of solute, Δμ2∘# were also calculated and discussed in terms of transition state theory. It has been observed that there exist strong solute–solvent interactions in these systems and these interactions increase with increase in sucrose concentration in solution.