Influence of the composition of aqueous-alcohol solvents on the thermodynamic characteristics of l-phenylalanine dissolution at 298.15 K

The enthalpies of l-phenylalanine dissolution in aqueous methanol, ethanol, 1-propanol and 2-propanol have been determined by calorimetry at 298.15 K and alcohol mole fractions up to x2 ∼0.4. The standard enthalpies of solution ΔsolH° and transfer ΔtrH° from water to the mixed solvent as well as the enthalpy coefficients of l-phenylalanine–alcohol pair-wise interactions were calculated. The interrelation of the enthalpies of dissolution and transfer for l-phenylalanine with structural features of alcohols has been determined. A comparative analysis of the thermodynamic characteristics of dissolution of l-phenylalanine and some other amino acids (glycine, l-alanine, l-threonine and l-valine) in the mixtures studied has been made.