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

Viscosities and densities of aqueous solutions of glycine, DL-alanine, DL-a lpha-amino-n-butyric acid, DL-valine, DL-leucine and L-serine have been mea sured as a function of amino acid concentration at 278.15, 288.15, 298.15 a nd 308.15 K. These data have been used to calculate the apparent molar volu mes 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 fr om 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 b y application of the transition-state theory to the B-coefficient data, and the corresponding activation enthalpy Delta H-2(0 not equal) and entropy D elta 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 activatio n 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 transi tion state of these solutions have been made. (C) 1999 Elsevier Science B.V . All rights reserved.