INFLUENCE OF BORIC ACID ON THE HYDROLYSIS RATE OF A HYDROXY SCHIFF BASE.

Article abstract of DOI:10.1246/bcsj.57.500

Effects of boric acid on the rate of hydrolysis of a Schiff base derived from alpha -hydroxyisobutyrophenone and 2-methoxyethylamine were examined in the pH range 4. 2-10. 4 at 30 degree C. The rate increased above pH 7 but decreased below pH 7 with increasing borate concentration following a saturation curve. This is consistent with a reaction sequence involving a preequilibrium formation of a borate-substrate complex followed by its rate-determining decay to the hydrolysis products. The formation constant of the complex showed a bell-shaped change with pH but the rate constant for the complex decay was constant above pH 7, a small change being observed at lower pH. A mechanism involving an intramolecular transfer of the boron-coordinated hydroxide ion to the imine carbon within the complex is presented.