The crystal and molecular structure of trehalose dihydrate

Abstract

The crystal structure of trehalose dihydrate has been solved by direct methods and refined to an R index of 0-057 using anisotropic refinement. The space group is P212121 and four formula units of C12HzzOz~.2HzO are contained in the unit cell of dimensions a= 17.90, b= 12.21 and c= 7.586 A. The two glucopyranose residues in the trehalose molecule have the chair 4C1 form, and are bonded by the a 1 --+ 1 glycosidic link in approximate twofold symmetry. Departures from symmetry are found in torsion angles about the e 1 -+ 1 link and in conformations of the primary alcohol groups O(6)H and O(6')H. The C-O bond lengths show systematic trends similar to those in other e-pyranose sugars and at the same time show some characteristic features related to the e 1 -~1 link of the two glucose residues. There are two indirect intramolecular hydrogen bonds incorporating water molecules. Neither the ring oxygens nor the glycosidic linkage oxygen accept hydrogen bonds. The molecular packing in the crystal is mainly determined by the hydrogen bonds.