Thermodynamics of DL-alalnyl-DL-asparagine dissolution in water–organic mixtures at 298.15 K

Enthalpies of dissolution of DL-α-alanyl-DL-α-asparagine (AlaAsn) in aqueous solutions of acetonitrile, 1,4-dioxane, acetone, and dimethyl sulfoxide are measured via calorimetry at T = 298.15 K and organic solvent concentrations x 2 = 0–0.3 mole fractions. Standard values of the enthalpy of dissolution (Δsol H°), transfer (Δtr H°) of AlaAsn from water into mixed solvent, and enthalpic pair interaction coefficients (h xy ) of AlaAsn with molecules of organic solvents are calculated on the basis of experimental data. The effect the composition of a water–organic mixture has on the enthalpy characteristics of AlaAsn is considered. The correlation between the enthalpy of dissolution and the transfer of AlaAsn and the structure and properties of the solvents used is demonstrated.