Complexation of aliphatic alcohols by alpha- and beta-cyclodextrins and their partial methylated derivatives in aqueous solution

The complexation of aliphatic alcohols by alpha- and beta-cyclodextrins and their partially methylated derivatives has been studied by means of calori metric titrations in aqueous solution. The methyl substituents have no pron ounced influence upon the complex formation. alpha-Cyclodextrin and the par tially methylated derivative form with only few exceptions more stable than beta-cyclodextrin. With increasing chain length of the alcohols the values of the stability constants and reaction enthalpies increase in case of the complex formation with alpha-cyclodextrin and partially methylated alpha-c yclodextrin. In contrast the complex formation becomes disfavoured by the r eaction entropy with an increasing number of methylene groups. The values o f the reaction enthalpies with the beta-cyclodextrins are close to zero. Th us the complexation is only favoured by entropic contributions.