Volumetric and viscometric behaviour of some amino acids and their group contributions in aqueous tetramethylammonium bromide at different temperatures

Abstract

Densities, ρ and viscosities, η for L-serine, L-threonine, L-glutamine, L-lysine, L-arginine and L-histidine (0.05-0.25 m) in 0.20 m aqueous tetramethylammonium bromide were determined at 298.15, 303.15, 308.15, and 313.15 K. The density data was used to compute apparent molar volume, φν. The partial molar volume, φν0, at infinite dilution and experimental slope, Sν*were obtained from Masson's equation and interpreted in terms of solute-solvent and solute-solute interactions, respectively. The φν0 values are found to vary with temperature as a power series of temperature. The structure-making/-breaking ability of solute were discussed using Hepler's criterion. The partial molar volumes of transfer, φν0(tr) of amino acid from aqueous to aqueous tetramethylammonium bromide solution were interpreted in the light of cosphere overlap model. The viscosity data was utilized to determine A- and B-coefficients of viscosity, free energy of activation of viscous flow, Δμ10* and Δμ20*, per mole of solvent and solute, respectively, and ΔH* and ΔS*were also evaluated. The linear variation of φν0 and B-coefficient with the number of carbon atoms in the alkyl chain of amino acids was utilized to determine the respective contributions of (NH3+, COO-) and CH 2 groups to φν0 and B-coefficient, respectively. © by Oldenbourg Wissenschaftsverlag.