Relative gas-phase acidities of glucopyranose from molecular orbital calculations

Abstract

AM1 and ab initio calculations were performed for molecular glucopyranose and its alkoxy anions. Minimum energy conformers were found for both the α- and β-anomers of molecular glucose and each of the corresponding deprotonated species. Cooperative hydrogen bonding towards the charge site was observed for the anions, which is similar to the cooperative counterclockwise hydrogen bonding that occurs with the neutral molecular species. The anomeric hydroxyl was found to be the most acidic hydroxyl group for α-glucopyranose, while the C(4) hydroxyl was the most acidic site for the β-anomer. In all cases the primary hydroxyl at C(6) was the least acidic site. Copyright © 1999 John Wiley & Sons, Ltd.