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

Resumo

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 Т = 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.