Hydration and dehydration of pyruvic acid

Abstract

The reaction rates and equilibria involved in the hydration and dehydration of pyruvic acid have been investigated by the n.m.r. technique for solutions from pH 6 to hydrochloric acid concentration 4M. Dissociation constants were estimated (from the equilibria and changes in chemical shifts) to be pK 1·5 for the unhydrated acid and pK 3·0 for the hydrated acid. Both hydration and dehydration reactions are hydrogen ion-catalysed, but the latter is in addition subject to general acid catalysis and its rate also varies inversely as the square of the water concentration. A tentative mechanism for dehydration based on this dependence on water concentration is discussed.