Dependence of the enthalpies of alanyl-alanine dissolution on the composition of mixed water + acetone and water + DMSO solvents at 298.15 K

Abstract

The enthalpies of dissolution of two dipeptides, DL-α-alanyl-β-alanine and β-alanyl-β-alanine, in mixed solvents H 2 O + acetone (AC) and H 2 O + dimethyl sulfoxide (DMSO) are measured via calorimetry at an organic component concentration of x 2 = 0-0.25 mole fraction at 298.15 K. The standard enthalpies of dissolution ( ) and the transfer ( ) of dipeptides from water to the mixed solvent and the enthalpic coefficients of pairwise interactions (h xy ) with AC and DMSO molecules are calculated from these data. The effect the composition of aqueous organic mixtures has on the enthalpy characteristics of the dissolution of DL-α-alanyl-β-alanine and β-alanyl-β-alanine is considered. A comparative analysis of h xy values is performed for alanine dipeptides in the investigated mixed solvents.