Enthalpies of dilution of glycine and l-alanine in aqueous 1-propanol solutions at TÂ =Â 298.15 K

The dilution enthalpies of glycine and l-alanine in aqueous 1-propanol solutions have been measured by a mixing-flow microcalorimeter at T = 298.15 K. The homogeneous enthalpic interaction coefficients of the two zwitterions have been calculated according to the analysis of the excess enthalpy suggested by Friedman [J. Solution Chem. 1 (1972) 387-390]. The enthalpic pairwise interaction coefficients h2 of glycine are negative and pass through a minimum with increasing 1-propanol content in mixed solvents, while those of l-alanine decrease from positive to negative. The variations of the enthalpic pairwise interaction coefficients are interpreted in terms of solute − solute and solute − solvent interactions.