Enthalpies of solution of l-threonine in a (water + alcohol) mixture at 298.15 K

The enthalpies of solution of l-threonine in the (water + methanol), (water + ethanol), (water + n-propanol), and (water + i-propanol) mixtures, with an alcohol content up to 0.4 mol fractions, have been measured calorimetrically at T = 298.15 K. The standard enthalpies of solution and transfer of l-threonine from water to an aqueous alcohol have been calculated. The effect of the structure properties of the mixed solvent on the specified enthalpy characteristics of l-threonine is discussed. The enthalpy coefficients of pairwise interactions between amino acid and alcohol molecules have been computed. It has been found that these coefficients become increasingly positive in the methanol, ethanol, n-propanol, and i-propanol consequence. A comparative analysis of the thermodynamic characteristics of dissolution of l-threonine and some other amino acids (glycine, l-alanine and l-valine) in the mixtures studied has been made.