I need dry DMSO for a
reaction.Dimethyl sulfoxide (DMSO) is a hygroscopic material. I am
suggesting here common methods to dry DMSO.
- Vacuum Distillation Method. A convenient method of preparing nearly anhydrous DMSO is to add approximately 20% excess DMSO to the reaction vessel and remove the excess and water by slow distillation through a packed column under vacuum.To distill this nearly anhydrous DMSO, non- jointed, all-glass equipment is required. For the majority of applications, removal of most of the water as a distillation forerun is adequate. It is convenient and requires no special equipment. For cases where very dry DMSO is needed, the next method gives a product with negligible water content.
- Molecular Sieves Drying Method. DMSO can be dried to 10 ppm water or less using Linde molecular sieves. A glass column (5' x 1" ID )was packed with one pound molecular sieves (4Å, 14 x 30 mesh). It was activated by heating 16 hours at 325°C, with an ar- gon flow of 6-7 ft 3 /hr. Thirty liters of DMSO with 270 ppm (0.027%) water were passed through this column. At the mid- point, the DMSO may contained 6-10 ppm water. The second half may contain 15-30 ppm. Column regeneration requires washing the column first with DMSO containing 10% water, then 50% DMSO-50% water and finally with water. An extreme heat buildup results from an initial water wash due to heat of solution of DMSO. Repeat the activa- tion step described above after the wash. For this Molecular sieve of 4nm is used.
- Distillation from CaH 2 : Distillation from calcium hydride has been widely used in literature reports. However, this procedure has been found to be less effective and less convenient than the first two methods described above. Typically, calcium hydride powder is stirred with DMSO in a flask vented through a phosphorus pentoxide tube. After 18 hours, the distillate (bp 4 mm Hg, 64°C) may contain 90 ppm water. After 7 days exposure, the distillate may still contain 25 ppm water.
References
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