Preprint: Phenyl boronic acid complexes of diols and hydroxyacids.




Bromba, Caleb
Carrie, Philippa
Chui, Jonathan
Fyles, Thomas M.

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Cumulative formation constants for the interaction of phenylboronic acids with 1,2-diols and structurally related alpha-hydroxy carboxylic acids were determined by potentiometric titration in aqueous solution. Although there is a significant electronic effect on the acidity of phenylboronic acid (ρ = 2.1), there is no marked electronic effect on the stability of the complexes. Rather, the complexes are significantly destabilized by adjacent anionic groups, by steric interactions across the face of the cyclic boronate ester, and by angle strain within the boronate ester ring. Binding that is nearly independent of pH is observed for some favorably constituted alpha-hydroxy acid complexes as a result of the relatively high acidity of the acids, which in turn allows tetrahedral boronate complexes to persist in acidic solution (pH < 3).


Preprint as submitted to Supramolecular Chemistry. Final paper available at


boronic acids, molecular recognition, formation constant, titration