Dimethyl sulfoxide

Dimethyl Sulfoxide (DMSO, empirically C₂H₆OS), also known as methyl sulfoxide, dimethyl sulphoxide, dimethylsulfoxide, methylsulfinylmethane or sulfinylbismethane, is a sulfur-containing organic chemical compound. It is a clear, colorless hygroscopic liquid with a smell that reminds of garlic. DMSO belongs to the class of "dipolar aprotic solvents" which includes also dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone. It is readily soluble into a wide range of organic solventes such as alcohols, esters, ketones, chlorinated solvents and aromatic hydrocarbons. It is also miscible in all proportions with water.

Dimethyl sulfoxide is a by-product of wood pulping and is frequently used as solvent in a number of chemical reactions. In particular DMSO proved to be an excellent reaction solvent for SN2 alkylations: it is possible to alkylate indoles with very high yields using potassium hydroxide as the base and a similar reaction also occurs with phenols. DMSO can be reacted with methyl iodide to form a sulfoxonium ion which can be reacted with sodium hydride to form a sulfur ylide.

Uses

DMSO was discovered in 1867, but was not used commercially until after WWII. Other than its use as a solvent, both in organic synthesis and industrial applications (polymer chemistry, pharmaceuticals and agrochemicals), DMSO also makes a very good paint stripper: it is able to remove many paints from both wood and metal in a small amount of time. It is thought to be much safer than many of the other chemicals used as paint strippers, such as nitromethane and dichloromethane. DMSO is also employed as a rinsing agent in the electronics industry and, in its deuterated form (DMSO-d6), is a useful solvent in NMR due to its ability to dissolve a wide range of chemical compounds and its minimal interference with the sample signals. In cryobiology DMSO has been used as a cryoprotectant and is still an important constituent of cryoprotectant vitrification mixtures used to preserve organs and tissues.

Use of dimethylsulfoxide in medicine dates from around 1963, when a University of Oregon Medical School team, headed by Stanley Jacob, discovered it could penetrate deeply through the skin and other membranes without damaging them and had effects of its own or could 'carry' other compounds deep into a biological system. Infact by dipping a finger into DMSO, it should be possible to perceive its taste in a matter of seconds. In the medical field DMSO is predominantly used as a topical analgesic, as an anti-inflammatory and as antioxidant. It has been examined for the treatment of an extraordinary number of conditions and ailments. The FDA has approved DMSO usage only for the palliative treatment of interstitial cystitis. Morover it is commonly used as a liniment for horses, although its use in humans is controversial.

Safety

Dimethylsulfoxide is irritant in case of on ingestion and contact with eyes, skin and the respiratory tract. While DMSO is much less harmful than DMF or HMPA, prolonged exposure to this substance can cause dermatitis and possibly damage the liver or kidneys. The biggest concern with DMSO is its ability to transfer other substances into the human body through skin contact. For instance a solution of sodium cyanide in DMSO has a far greater ability to cause cyanide poisoning through skin contact than either solid sodium cyanide or an aqueous solution.