New approach to the equilibrium of D-glucaric acid in water: DFT study of tetrahedral intermediates

The present study aims at investigating, for the first time, the formation of tetrahedral intermediates during the equilibrium mechanism of D-glucaric acid in water. In this work, carried out at B3LYP/6-31+G(d,p) computational level in vacuum and using the polarizable continuum model, two systems are proposed and simulated: the first describes an intramolecular proton transfer, and the second requires the intervention of solvent molecules for the proton transfer. The second system, simulated in vacuum, indicates greater ease in establishing this equilibrium due to a significant reduction in angular tensions. Also, the idea of a tetrahedral intermediate carrying two geminal diol groups constitutes a favorable hypothesis due to the low energy barriers calculated as well as a better structural flexibility generated following the equilibrium of the tetrahedral intermediates between them. Experimental confirmation of the presence of such a powerful tetrahedral intermediate would be a considerable advance in resolving the equilibrium mechanisms of D-glucaric acid.