Properties of cyclodextrins: Part IX Specific inclusion compound formation of cyclodextrin derivatives with hexane and 2,3‐dimethylbutane in aqueous solution

Abstract On the basis of thermodynamic data concerning inclusion compounds of α and β‐cyclodextrin derivatives with hexane (hex) and 2,3‐dimethylbutane (DMB) in aqueous solution, as reported in earlier publications in this series, a model of the inclusion complex is suggested. This model comprises: A real inclusion compound (“fit in”) is formed in solution. Almost all derivatives form inclusion compounds with hex and DMB in which the mole ratio is 1:1 (conclusion of Part VIII of this series). α‐Cyclodextrin derivatives include in the voids hex molecules in their stretched form, whereas DMB molecules do not fit entirely into the voids. In both cases this causes a considerable disturbance in the water structure around the cyclodextrin molecules. β‐Cyclodextrin derivatives include hex molecules in their coiled form and DMB molecules fit entirely into the voids. The water structure is hardly affected. This model appears to be in agreement with considerations of space filling of the guest molecules in the cyclodextrin voids. Furthermore, in comparing the inclusion process with the dissolution of apolar compounds in different solvents, the model is confirmed. Also, comparison of the interaction among the different cyclodextrin derivatives is in agreement with the model.