Formation of Inclusion Complexes of Cycldextrin with Ethanol under Anhydrous Conditions.

Complex formation of poorly water soluble organic compounds with cyclodextrin (CD) is quite difficult in an aqueous cyclodextrin system. Formation of the inclusion complex of d-limonene, phenyl ethanol, acetophenone, or menthol was investigated in a slurry form of α-, β-, or γ-CD in organic solvents or alcohol under anhydrous conditions. Ethanol and methanol were found to be good solvents for this method. The use of ethanol as the solvent was investigated in greater detail. There existed an optimal amount of ethanol for the maximum inclusion of d-limonene as the guest compound. However, an excess of ethanol inhibited the inclusion. An adsorption model of alcohol on CD, analogous to the substrate inhibition model of enzyme kinetics, could correlate the inclusion ratio with the amount of alcohol added to CD.