The saturation molality of alpha-D-xylose(cr) in water was measured by using HPLC and is m(sat) = (8.43 ± 0.42) mol∙kg-1 at the temperature T = 298.15 K. It was also established that the anhydrous form of alpha-D-xylose(cr) is the crystalline form that is in equilibrium with the aqueous solution at T = 298.15 K. Solution calorimetry was used to measure the following standard molar enthalpies of solution at T = 298.15 K: ΔsolHom = (12.10 ± 0.12) kJ∙mol-1 for alpha-D xylose(cr); ΔsolHom = (8.1 ± 2.7) kJ∙mol-1 for 1,4-alpha-D-xylobiose(am); and ΔsolHm = -(24.1 ± 6.4) kJ∙mol-1 for 1,4--D-xylotriose(am). It was observed that both 1,4-beta-D-xylobiose(am) and 1,4-beta-D-xylotriose(am) were amorphous substances and that they form thick gels in water in which no solid phase is present. Consequently, it is not possible to measure m(sat) for these two substances. All substances were carefully characterized by using both HPLC and Karl Fischer analysis. NMR was used to measure the anomeric purity of the alpha-D-xylose(cr). Thermodynamic network calculations were used to calculate standard molar formation properties for the aforementioned substances.
Citation: Journal of Chemical Thermodynamics
Pub Type: Journals
enthalpy of solution, saturation molality, solubility, standard formation properties, 1, 4 ¿ D xylobiose, 1, 4-beta-D-xylotriose, alpha-D-xylose.