Thermodynamic characteristics, structure, and interactions of L-proline in aqueous solutions of alcohols and urea

The enthalpies of dissolution of imino acid L-proline in aqueous solutions of methanol, 2-propanol, ethylene glycol, glycerin, and urea are measured by the calorimetric method at 313.15 K. Enthalpic parameters of the interaction of L-proline with nonaqueous components are calculated and compared with the data at 298.15 K. It is found that the sign of the heat capacity parameter of the pair and ternary interactions depends on whether the nonaqueous solvent component is a destroyer or stabilizer of the water structure. Partial molar heat capacities of proline in mixed solvents are obtained by the integral dissolution heat method. Temperature changes in the reduced enthalpy and entropy of the proline solution are determined at an increase in the temperature from 298 K to 313 K. It is shown that there is entropyenthalpy compensation at temperature changes in the characteristics during dissolution.