Thermochemistry of the Dissolution of L-Threonine in Acetonitrile, 1,4-Dioxane, Acetone, and Dimethylsulfoxide Aqueous Solutions at Т = 298.15 K

Abstract

The enthalpies of dissolution of L-threonine in acetonitrile, 1,4-dioxane, acetone, and dimethylsulfoxide aqueous solutions are measured via calorimetry at mole fraction of the organic solvent x2 = 0–0.25 and T = 298.15 K. Standard enthalpies of dissolution $${{\Delta }_{{{\text{sol}}}}}H^\circ $$ and transfer $${{\Delta }_{{{\text{tr}}}}}H^\circ $$ of L-threonine from water to a mixed solvent are calculated along with the enthalpy coefficients of pairwise interactions hxy between L-threonine and the solvent molecules. Relationships between the enthalpies of dissolution of L-threonine and the composition of a mixture, the energy of interaction between the components of the mixture, and the electron-donating ability of organic solvents are found. The enthalpy coefficients of the pairwise interaction between L-threonine and other amino acids (glycine, L-alanine, L-valine, and L-methionine) in the mixed solvents are analyzed comparatively. The enthalpy contributions from the side chains of L-amino acids to the energy of interaction with molecules of these organic solvents in an aqueous solution are assessed quantitatively.