COMPLEXATION CHEMISTRY OF CYCLOHEXAAMYLOSES .4. REACTIONS OF CYCLOHEXAAMYLOSE WITH FORMIC, ACETIC, AND BENZOIC-ACIDS AND THEIR CONJUGATE BASES

pH potentiometric and 13C NMR analyses of aqueous solutions of cyclohexaamylose and formic-formate, aceticacetate, or benzoic-benzoate acid-base conjugate pairs indicate that only binary complexes form with each of the acids and with benzoate anion. Equilibrium constants for these complexation reactions are measured between 15 and 50 °C. These results yield thermodynamic parameters ∆H° and ∆S° for each complex formation. Interpretation of 13C NMR resonances of cyclohexaamylose and substrate carbons of the various complexes indicates preferential binding of the acids within the narrow zone and of the benzoate anion within the wide zone of the cyclohexaamylose cavity. © 1979, American Chemical Society. All rights reserved.