BINDING OF SUBSTITUTED ACETIC-ACIDS TO ALPHA-CYCLODEXTRIN IN AQUEOUS-SOLUTION

Complex binding constants of 23 aliphatic acids with alpha-cyclodextri n in aqueous solution were measured by potentiometry, solubility, or c ompetitive spectrophotometry at 25 degrees C. All systems formed 1:1 a cid:cyclodextrin complexes, and some of them also formed 1:2 complexes . The conjugate acids formed stronger complexes than did the conjugate bases (except for glycine). Empirical correlations of complex stabili ties are shown with partition coefficients surface areas, molar refrac tion, and other descriptors Complex stability appears to result from t he hydrophobic effect, the dispersion interaction, and interaction oi the carboxylic acid group with the cyclodextrin.