The crystal structure of sucrose sodium bromide dihydrate

The complete crystal structure of sucrose sodium bromide dihydrate has been determined. The crystals are orthorhombic, with space-groupP 21 21 21 , and cell-edgesa =21.92,b =9.72,c =8.43 A. The bromine positions were obtained from Patterson-Harker syntheses, and the signs of theF ’s of the (0kl ), (h 0l ) and (hk 0) planes from the change of intensity from the chloride to bromide compounds. Fourier projections parallel to the three axes were used to determine the complete structure. In the structure the pyranose ring of the molecule is of the Sachsetrans form. The furanose ring is an unexpectedly compact grouping, and one member of the ring is displaced from the plane of the other four. The configuration of both rings is such as to allow the groups attached to the ring atoms to approach as nearly as possible to the mean plane of each ring. Direct proof that sucrose may be described asα -d -glucopyranosido-β -d -fructofuranoside has been obtained for the first time. The sucrose molecules are held together by bonds from the hydroxyl groups to the Na and Br ions and to the water molecules, the hydroxyl groups each having two external bonds. The method used of reducing the observed intensities to an absolute scale is described, and the proof of the correctness of the structure is given as a set of diagrams of calculated and observed electron density.