Apparent molar volumes and viscosity B-coefficients of some α-amino acids in aqueous solutions from 278.15 to 308.15 K

Viscosities and densities of aqueous solutions of glycine, DL-alanine, DL-alpha-amino-n-butyric acid, DL-valine, DL-leucine and L-serine have been measured as a function of amino acid concentration at 278.15, 288.15, 298.15 and 308.15 K. These data have been used to calculate the apparent molar volumes V-2,V-phi and viscosity B-coefficients. The calculated standard partial molar volumes V-2,phi(0) and B-values were split into the contributions from the (NH3+,COO-) and CH2 groups by linear correlations. Free energies of activation, Delta(mu 2)(0 not equal) of aqueous amino acids were obtained by application of the transition-state theory to the B-coefficient data, and the corresponding activation enthalpy Delta H-2(0 not equal) and entropy Delta S-2(0 not equal) were also given. On the basis of the contributions of (NH3+, COO-) and CH2 groups to V-2,phi(0), B-coefficient and the activation parameters, comments on the effect of amino acids and their groups on the structure of water and the relative orderness of the ground and the transition state of these solutions have been made. (C) 1999 Elsevier Science B.V. All rights reserved.