Volumetric and Viscometric Behaviour of some Amino Acids and their Group Contributions in Aqueous Tetramethylammonium Bromide at Different Temperatures

Abstract

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, φ v . The partial molar volume, φ v 0, at infinite dilution and experimental slope, S v * were obtained from Masson´s equation and interpreted in terms of solute-solvent and solute-solute interactions, respectively. The φ v 0 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, φ v 0 (tr) of amino acid from aqueous to aqueous tetramethylammonium bromide solution were interpretedin 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, Δμ 1 0 * and Δμ 2 0 *, per mole of solvent and solute, respectively, and ΔH * and ΔS * were also evaluated. The linear variation of φ v 0 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 CH2 groups to φ v 0 and B-coefficient, respectively.