Dimethyl sulfoxide

Dimethyl sulfoxide
General
Systematic name	Dimethyl sulfoxide
Other names	Methyl sulfoxide methylsulfinylmethane DMSO
Molecular formula	C₂H₆OS
SMILES	CS(C)=O
Molar mass	78.13 g/mol
Appearance	Clear, colorless liquid
CAS number	^*
Properties
Density and phase	1.1004 g/cm³, liquid
Solubility in water	Miscible
Solubility in ethanol, benzene, chloroform	Miscible
Melting point	18.5 °C (292 K)
Boiling point	189 °C (462 K)
Viscosity	1.996 cP at 20 °C
Acid dissociation constant	35 (in DMSO)
Structure
Dipole moment	3.96 D
Hazards
MSDS	External MSDS
Main hazards	Irritant (Xi)
NFPA 704
R-phrases
S-phrases	,
Flash point	95 °C
RTECS number	PV6210000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related Sulfoxides	diethyl sulfoxide
Related compounds	dimethyl sulfide, dimethyl sulfone, acetone
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox

Dimethyl sulfoxide (DMSO, molecular formula C₂H₆OS), also known as methyl sulfoxide, dimethyl sulphoxide, dimethylsulfoxide, methylsulfinylmethane or sulfinylbismethane, is a sulfur-containing organic compound. It is a clear, colorless hygroscopic liquid. When it is pure it has little odor, but impure samples smell strongly of dimethyl sulfide. 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 solvents 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 S_N₂ 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. The methyl hydrogens of DMSO are somewhat acidic in character (pK_a=35) due to the stabilization of the resultant anions by the sulfoxide group.

It is important to use caution in handling dimethyl sulfoxide, due to its strong solvent power and the ease with which it penetrates the skin. It is especially important to avoid contact with the mucous membranes.

In certain conditions, dimethly sulfoxide can produce an explosive reaction when exposed to acid chlorides.

One of the leading suppliers of DMSO is the Gaylord company in the USA.

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.

In organic synthesis, DMSO can also be used in a number of oxidation reactions, the Pfitzner-Moffatt oxidation and the Swern oxidation.

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, tissues, and cell suspensions. It is particularly important in the freezing and long-term storage of embryonic stem cells and hematopoietic stem cell, which are often frozen in a mixture of 10% DMSO and 90% fetal calf serum. As part of an autologous bone marrow transplant the DMSO is re-infused along with the patient's own hematopoietic stem cell.

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 could carry other compounds deep into a biological system. Some people report an onion- or garlic-like taste after contact with the skin. This is likely due to catabolic processes which reduce DMSO to dimethyl sulfide. In the medical field DMSO is predominantly used as a topical analgesic, a vehicle for topical application of pharmaceuticals, as an anti-inflammatory and an antioxidant. It has been examined for the treatment of an extraordinary number of conditions and ailments. The Food and Drug Administration (FDA) has approved DMSO usage only for the palliative treatment of interstitial cystitis. Because it was first used several decades ago, it is currently not possible to patent it because of the 17 year length of pharmaceutical patents. This largely explains why little research is done into its possible therapeutic roles, because without the possibility of future patent protection, pharmaceutical companies rarely fund research on a drug. (Another substance having obvious therapeutic effect but not FDA approved for use as a drug is melatonin.) Also, DMSO is commonly used in the veterinary field as a liniment for horses.

Dimethyl sulfoxide is the most powerful readily available organic solvent. It dissolves a great variety of organic substances to the highest loading level, including carbohydrates, polymers, peptides, as well as many inorganic salts and gases. Loading levels of 50-60 wt. % are often observed with DMSO (compared with l0-20 wt. % with typical solvents). Therefore it plays a vital role in sample management and High-throughput screening operations in drug design .

Safety

Dimethylsulfoxide is an irritant in cases of ingestion and contact with eyes, skin and the respiratory tract. While DMSO has a low toxicity ^*, and is less harmful than DMF or HMPA, prolonged exposure can cause dermatitis and possibly damage the liver or kidneys. The biggest toxicological concern surrounding 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.

References

Epstein, W.W. , Sweat, F.W. Chemical Reviews 1967, 247-260. (Review)
Tidwell, T.T. Synthesis 1990, 857-870. (Review)
Balakin, K.V., Savchuk, N.P., Tetko I.V. Curr. Med. Chem. 2006, 13(2), 223-41. (Review)

External links

Solvents | Organosulfur compounds

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Uses

Safety

References

External links