Thermodynamics and temperature dependence of dissociation and solvation of alpha-alanine in H 2O-MeOH and of valine in H 2O-PrOH-2

Abstract

Thermodynamic constants of amino acid dissociation with carboxylic, K 1, and amino groups, K 2, and standard thermodynamic functions of dissociation (Δ G 0 d,1, Δ G 0 d,2, Δ H 0 d,1, Δ H 0 d,2, Δ S 0 d,1, Δ S 0 d,2) of α-alanine in methanol–water solvent and of valine in propan-2-ol-water solvent (0, 20, 40, 60, 80 wt.%) have been determined by potentiometric method in galvanic cells without liquid junction at 278.15–328.15 K (with step of 10 K). The standard Gibbs energy of transfer of ionic forms of α-amino acids in MeOH-H 2O, PrOH-2-H 2O mixtures have been calculated. The short-range interaction part of dissociation Gibbs energy, Δ G 0 d,1,2 ⁎ have been obtained assuming the borders of ionic association area.