Molecular Dimensions and Crystal Structure of Dimethyl Sulphoxide at −60° C

Abstract

Dimethyl sulphoxide (DMSO) has been much discussed and investigated in recent years because of its remarkable properties in medicine and as a solvent. We have now determined its molecular dimensions and crystal structure, at −60° C, from an analysis of three-dimensional X-ray diffraction data. The sample, being a liquid at room temperature, was enclosed and sealed inside a Lindemann glass capillary of 0.3 mm diameter. It was crystallized, in situ, inside a low-temperature Weissenberg camera by slow freezing, melting and refreezing with a jet of cold gas obtained by boiling liquid oxygen. The to-and-fro horizontal movement of the crystal goniometer shaft, involved in this process, was made sufficiently slow and mechanical by coupling the shaft to the spindle of the camera motor by suitable reduction gears. Crossed polaroids mounted on the camera base were used to ensure the quality of the crystal, before single-crystal X-ray pictures were taken. Using copper Kα radiation, rotation and hkL (L = 0,1,2,3) equi-inclination intensity data (on multiple films) were collected.