Volumetric and viscometric study of amino acids in aqueous sorbitol solution at different temperatures

Abstract

Densities (ρ) and viscosities (η) of glycine, l-alanine, l-valine, l-threonine and l-arginine in (0.2, 0.4, 0.6, 0.8 and 1.0)mol·kg−1 aqueous sorbitol solutions have been measured at T=(293.15, 303.15, 313.15 and 323.15)K under atmospheric pressure. The apparent molar volume (Vφ) and the limiting partial molar volumes of amino acids (Vφ0) were calculated through the density data. And the limiting partial molar volumes of transfer (ΔtrVφ0) and interaction coefficients Vab, and Vabb were also determined. The extended Jones–Dole equation was used to correlate the viscosities in order to obtain viscosity B-coefficient and the free energies of activation per mole of solvent (Δμ10≠) and solute (Δμ20≠). The limiting partial molar volume of transfer and the free energies of activation per mole of both solvent (Δμ10≠) and solute (Δμ20≠) were discussed on the basis of the co-sphere overlap model and transition state theory, respectively. The hydration number of amino acids was computed using the obtained limiting partial molar volume and viscosity B-coefficient. Additionally, the group contribution method was applied to determine the respective contribution of (NH3+, COO−), CH2, OH and CNHNHNH2 to Vφ0 and B-coefficient.