Effect of Temperature on the Thermodynamic Characteristics of Acid–Basic Reactions in Aqueous Solutions of DL-Valyl-DL-leucine

Temperature effects of the reaction between a DL-valyl-DL-leucine solution and solutions of HNO₃ and KOH are measured via calorimetry in different ranges of pH, at temperatures of 288.15 and 308.15 K and ionic strengths of 0.5, 1.0, and 1.5 (using KNO₃ and LiNO₃ as background electrolytes). The thermal effects of the stepwise dissociation of the dipeptide are determined. Standard thermodynamic characteristics (Δ_rH°, Δ_rG°, Δ_rS°, $\Delta C_p^{\circ }$) are calculated for the acid–base reactions in aqueous solutions of DL-valyl-DL-leucine. The connection between the thermodynamic characteristics of dipeptide dissociation and the structure of this compound is considered.