Enthalpic Interaction Coefficients of N,N′-Hexamethylenebisacetamide with Glycine in Aqueous Glucose and Sucrose Solutions at 298.15 K

The mixing enthalpies of N,N'-hexamethylenebisacetamide (HMBA) with glycine in aqueous glucose and sucrose solutions have been determined by means of mixing-flow isothermal microcalorimetry at the temperature of 298.15 K. The heterotactic enthalpic interaction coefficients (h(xy), h(xxy), and h(xyy)) in the range of the saccharide molality, (0 to 1.5) mol center dot kg(-1), have been calculated according to the McMillan-Mayer theory. It has been found that the heterotactic enthalpic pairwise interaction coefficients h(xy) between HMBA and glycine in aqueous glucose and sucrose solutions are all positive and pass through a maximum, respectively, at about 0.3 mol center dot kg(-1) of glucose molality and about 0.6 mol center dot kg(-1) of sucrose molality. In the meantime, the value of h(xy) in aqueous glucose solutions is larger than that in aqueous sucrose solutions of the same molality. The variations of the heterotactic enthalpic pairwise interaction coefficients with the molality of sugar in mixtures are interpreted in terms of solute-solute and solute-solvent interactions.