Investigation of the Structure of Cyclodextrin Nitrates by the X-Ray Diffraction Method

The structure of alpha-, beta- and gamma-cyclodextrin nitrates was analyzed by X-ray diffraction. It has been established that with an increase in the number of nitrate groups in beta- and gamma-cyclodextrin nitrates, the structure changes from crystalline at a degree of substitution of hydroxyl group 9-12% to amorphous at that of more than 40%, which is a consequence of steric factors and different degrees of polarity of functional groups (OH) and (ONO2). In the case of alpha-cyclodextrin nitrates, with an increase in the degree of substitution of OH group, the tendency to amorphization of the substance, which is characteristic of beta- and gamma-cyclodextrin nitrates, remains. However, at a degree of substitution of 98-100% the appearance of a new crystalline phase is observed. Probably, the molecules of alpha-cyclodextrin nitrates, which have only 6 glucopyranose units in their composition, undergo structural changes due to steric effects, resulting in the formation of a new molecular crystal structure with a more stable configuration.