Crystal and molecular structure of methyl α- d-galactopyranoside 3-(sodium sulfate) monohydrate

Abstract

The crystal and molecular structure of methyl α- d-galactopyranoside 3-(sodium sulfate) monohydrate has been determined by X-ray diffraction. The molecular structure has a distorted chair conformation 4 C 1. The conformation of the hydroxymethyl group is gauche-cis and the methyl group is gauche-trans with respect to the pyranoid ring. The distorted sodium ion environment has seven closest oxygens of two different molecules. Coordination with (O-5, O-4, O-6) and (O-1, O-2), related by translational symmetry along the a axis, together with water oxygen O-1W and O-9 of the sulfate group, complete the first coordination sphere of sodium. A complex hydrogen-bond pattern involves all oxygens of the sulfate group as acceptors, linking molecules in [100] through O-7. The hydroxyl groups on C-2 and C-4 also participate in the bonding pattern. The complex packing by hydrogen bonds and ion coordination results in relevant differences with respect to the structure of other surface pyranosides.