Equilibria and reaction mechanism of the complexation of methylboronic acid with polyols

Methylboronic acid, CH 3 B(OH) 2 , forms 1:1 anionic complexes with polyols according to the reaction CH 3 B(OH) 2 +H 2 L⇔Cx - +H 3 O + . The polyols which were studied are 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, and 1,2,3-propanetriol. Complexes with both five-membered and six-membered chelate rings are formed. Equilibrium constants in the four systems vary between 10 -9 and 10 -10 , and they were determined by both pH titration and 11 B NMR spectroscopy