Thermodynamic and transport properties of l-serine and l-threonine in aqueous sodium acetate and magnesium acetate solutions at T = 298.15 K

Abstract

The apparent molar volumes, V 2, ϕ , apparent molar adiabatic compressibilities, κ S,2, ϕ , and relative viscosities, η r, of l-serine and l-threonine in different concentrations of aqueous sodium acetate and magnesium acetate solutions at T = 298.15 K have been obtained from the measurements of densities, speed of sound, and flow time, respectively. These data are used to derive the partial molar volumes, V 2 ∘ , partial molar adiabatic compressibilities, κ S , 2 ∘ (at infinite dilution), and viscosity B-coefficients. The corresponding quantities of transfer, (Δ t V 0, Δ t κ S , 2 ∘ , and Δ t B), have been obtained. The activation free energy, Δ μ 2 ∘ ≠ , for viscous flow has been calculated for l-serine and l-threonine in aqueous solutions. The hydration numbers, n H, side chain contributions, and interaction coefficients have also been calculated. The values of V 2 ∘ , κ S , 2 ∘ , viscosity B-coefficient, and Δ μ 2 ∘ ≠ for viscous flow increase with the concentration of sodium acetate and magnesium acetate solutions. The influence of magnesium acetate on the transfer properties is greater than sodium acetate in aqueous solutions. A comparison of Δ t V 0, Δ κ S , 2 ∘ , and Δ t B values for l-serine and l-threonine with the reported data for dl-α-alanine and dl-α-amino- n-butyric acid in aqueous sodium acetate and magnesium acetate solutions shows that the values are greater for l-serine and l-threonine at the same concentration of sodium acetate and magnesium acetate.