Physicochemical study of the processes of b-cyclodextrin hydrates dehydration

The research involved synthesizing b-cyclodextrin hydrates of the b-CD·nH2O (n = 11.9–0.9) composition. The obtained compounds were studied by powder X-ray diffraction (XRD), which revealed the transition from a monoclinic unit cell to an orthorhombic one with a decrease in the water content in the samples. The pressure of saturated vapor of the water in the b-CD·nH2O (n = 10.6–7.0) hydrates was measured by static tensimetry with membrane null-manometer over a wide temperature range (293–384 K) under conditions of a quasi-constant hydrate composition. The measured vapor pressure increases in proportion to the increase in the water content of the hydrate samples. The experimental data reduced to a single composition of b-CD·1H2O were approximated by the lnp(1/T) equation, from which the thermodynamic parameters (∆prH°T and ∆prS°T) of the process of b-cyclodextrin hydrate dehydration were calculated. This information was used to estimate the binding energies of the water molecules to the b-CD framework