Enthalpy of dilution and volumetric properties of N-glycylglycine in aqueous xylitol solutions at T = 298.15 K

Abstract

The enthalpy of dilution of N-glycylglycine (Δ dil H m) in aqueous xylitol solutions has been determined by means of flow-mix isothermal microcalorimetry at the temperature of 298.15 K. The homogeneous enthalpic interaction coefficients ( h 2, h 3, and h 4) which characterize the interactions of examined N-glycylglycine in aqueous xylitol solutions have been calculated according to the excess enthalpy concept based on the values of dilution enthalpy. It has been found that the enthalpic pair interaction coefficients ( h 2) in the systems investigated are negative and become less negative as the molality of xylitol increases. Values of the density ( ρ) of the ternary homogeneous systems were also measured with a quartz vibrating-tube densimeter at the temperature of 298.15 K. The values of the apparent molar volume ( V ϕ ) of the ternary systems were calculated from the data of density, which have been used to deduce limiting partial molar volumes of N-glycylglycine ( V ϕ o ) and limiting partial molar volumes of transfer ( Δ trs V ϕ o ) from water to aqueous xylitol solutions at different concentrations. The results have been discussed based on solute–solute interactions and solvation effects.