Interaction of boric acid and borates with carbohydrates and related substances

Abstract

Association constants for the mannitol–borate and glucose–borate complexes were determined from potentiometric titration measurements using Antikainem's equation. The results obtained indicated that mannitol was a much stronger borate complexant than glucose, as predicted from their molecular structures. The analyses for the dissociation constants of the complexes H₃BO₃ indicated that the complexed H₃BO₃ was not a simple monobasic acid but probably a mixture of different acids, the composition of which depends on the ratio of undissociated to dissociated H₃BO₃ in solution. Infrared spectra of solid mixtures of H₃BO₃ and borate ions with mannitol, glucose and ribose indicated that only ribose formed a stable solid complex with undissociated H₃BO₃. All three polyols formed solid complexes with borate ions. The i.r. spectra indicated that the complexes were polymeric.