Carbohydrate–water interactions of p-nitrophenylglycosides in aqueous solution. Ultrasonic and densitometric studies

Abstract

Hydration behavior of carbohydrate molecules with the anomeric position blocked, a series of axial and equatorial p-nitrophenylglycosides with different stereochemistry, has been thermodynamically analyzed in aqueous solution as a function of concentration at 298.15 K. For this purpose, the speed of sound and the density of solutions were simultaneously and automatically measured with a technique and a method recently developed by us. From these experimental data, quantities such as the apparent molar volume, V_ϕ, the apparent molar isentropic compressibility, K_s,ϕ, and the hydration numbers, n_h, of the glycosides have been determined. The corresponding apparent molar properties at infinite dilution allow for the analysis of the carbohydrate–water interactions in terms of the effect of the stereochemistry on the hydration of the glycoside molecule, while their behavior with concentration give insight on the carbohydrate–carbohydrate interactions. The results have been also rationalized on the basis hydration models.