COMPLEX-FORMATION BETWEEN ALPHA-CYCLODEXTRIN AND AMINES IN WATER AND DMF SOLVENTS

Complexation between alpha-cyclodextrin (alpha-CD) and aliphatic amine s in water and DMF solvents was studied by calorimetry. Amines form co mplexes with alpha-CD in both solvents but the nature of the complexes is guile different. In DMF the amines donate a hydrogen from the amin e N-H group to the cyclodextrin forming a normal hydrogen bonded compl ex. In DMF solutions with large amine concentrations, complexes other than 1:1 are observed. In contrast, in aqueous environment the amines form inclusion complexes in which the amine alkyl group penetrates the alpha-CD cavity and is stabilized by van der Waals interactions. The equilibrium constants Sor the complexes formed in water solvent increa se with increasing alkyl chain length due to an entropy effect.