Crystalline β-cyclodextrin hydrate is non-stoichiometric with 10.5–12 waters per cyclodextrin molecule

Solid-state 13C NMR spectroscopy was used to follow the dehydration of β-cyclodextrin hydrate from 12 to 10.5 waters per cyclodextrin. The process takes place without loss of crystalline order, or the presence of a phase transition. The water molecules involved can best be described as space-filling guests enclathrated in the cyclodextrin cavity. Hence the hydrate is non-stoichiometric within the limits of 10.5–12 waters per cyclodextrin molecule. On the other hand, dehydration of crystalline α-cyclodextrin hexahydrate involves a phase transition.