Thermodynamic characteristics of acid-base equilibria of glycyl-glycyl-glycine in water-ethanol solutions at 298 K

摘要

The enthalpies of the acid dissociation of glycyl-glycyl-glycine zwitterions and triglycinium ions are determined calorimetrically in water-ethanol solvents containing 0.0, 0.10, 0.30, and 0.50 molar fractions of ethanol at ionic strengths of 0.1 (maintained by sodium perchlorate) and D cent = 298.15 K. It is found that increasing the ethanol content in the solvent enhances the endothermic effect of triglycinium ion dissociation and reduces the endothermic effect of glycyl-glycyl-glycine dissociation. The results are discussed in terms of the solvation thermodynamics.