Structural investigation on sodium-2-keto-l-gulonate-monohydrate

The crystal structure of sodium-2-keto-l-gulonate-monohydrate (NaC6H9O7⋅H2O, an intermediate in the manufacture of l-ascorbic acid), has been determined by single crystal X-ray diffraction. This hydrate crystallizes in the monoclinic space group P21 with a = 7.3893(6), b = 6.4507(5), c = 9.4036(7), β = 103.239(1) and Z = 2. The sodium cation is octahedrally coordinated to five oxygen atoms from four pyranose anions and one oxygen from a water molecule. These octahedra are the fundamental building blocks of a layered structure, where double layers of sodium ketogulonate alternate with a monolayer of water. Within the water layers the molecules form columns within which individual water molecules are hydrogen bonded to their neighboring water molecules in the direction of the column and to two neighboring sodium ketogulonate octahedra in a direction perpendicular to the columns.

► The crystal structure of sodium-2-keto-l-gulonate-monohydrate is determined. ► The crystal structure consists of alternate layers. ► Within the layers, the water molecules form columns. ► Structural rearrangement is required when solvent-mediated dehydration occurs. ► The departure of the water molecule requires a destructive–reconstructive mechanism.