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Dimethyl Sulfoxide (DMSO) is used as a solvent for chemical reactions involving salts, most notably in Finkelstein reactions and in other nucleophilic substitutions. DMSO is an effective pain relieving agent. It is also used in antifreeze or hydraulic fluids and utilized in the oxidation of thiols and disulfides to sulfonic acids. It is used to enhance dermal absorption of many chemicals. It is also used as a cryoprotectant and is added to cell media to reduce ice formation and thereby prevent cell death during the freezing process.
Powerful solvent for many inorganic ions, primarily due to solvation of the cations with consequent enhanced reactivity of the counter anions both in increased nucleophilicity and base strength. In DMSO, the relative nucleophilicities of the halide ions are reversed (F- > I-). The rate of aromatic fluorodenitration in a range of polar aprotic solvents was highest for DMSO: J. Fluorine Chem., 35, 591 (1987); see Potassium fluoride, 14130. For enhanced base strength, see e.g.: cyclization of ω-bromo acids to lactones by K2CO3: Org. Synth. Coll., 6, 698 (1988); exhaustive alkylation of ketones with KOH: Tetrahedron Lett., 31, 859 (1990).
Malonic and ß-keto esters can be conveniently decarboalkoxylated by heating in wet DMSO: J. Org. Chem., 43, 138 (1978), avoiding the need for separate hydrolysis and decarboxylation steps.
Tosylates or activated halides can be oxidized with DMSO to aldehydes and ketones (Kornblum oxidation). ɑ-Bromo ketones are oxidized at room temperature to ɑ-keto aldehydes: J. Am .Chem. Soc., 79, 6562 (1957). Benzylic halides, on heating in the presence of NaHCO3, give benzaldehydes: J. Am. Chem. Soc., 114, 6227 (1992). Under similar conditions at 150oC, primary alkyl iodides: J. Chem. Soc., 520 (1964), and alkyl chlorides and bromides in the presence of NaI: Synth. Commun., 16, 1343 (1986), are oxidized to aldehydes. Unactivated bromides have also been oxidized to aldehydes in the presence of Ag salts: Tetrahedron Lett., 917 (1974). For oxidation of benzyl alcohols to benzaldehydes, catalyzed by HBr, see: Synlett, 2041 (2002). DMSO is more often used in combination with a variety of activating agents for selective oxidation of primary and secondary alcohols to carbonyl compounds under very mild conditions. For examples, see: Oxalyl chloride, A18012, or Trifluoroacetic anhydride, A13614 (Swern oxidation), Acetic anhydride, L04295 (Albright-Goldman), N,N'-Dicyclohexylcarbodiimide, A10973 (Pfitzner-Moffatt), Sulfur trioxide-pyridine complex, A12202 (Parikh-Doering), Triphosgene, A14932 and Phenyl phosphorodichloridate, A10479. Reviews: Synthesis, 70 (1971); 165 (1981); 857 (1990).
DMSO is a very weak acid (pKa= 31) but can be deprotonated by NaH, giving "dimsyl sodium", which is a useful strong base e.g. for the Wittig reaction: J. Org. Chem., 28, 1128 (1963).
Aromatic amines can be substituted in the para-position by reaction with DMSO in the presence of conc. HCl with or without CuCl to give 4-aminobenzaldehydes: J. Chem. Soc., Perkin 1, 2235 (1992). The intermediate species is thought to be chloromethyl methyl sulfoxide.
Mozhzhukhina, N.; Longinotti, M. P.; Corti, H. R.; Calvo, E. J. A conductivity study of preferential solvation of lithium ion in acetonitrile-dimethyl sulfoxide mixtures. Electrochim. Acta 2015, 154, 456-461.
Song, S.; Huang, X.; Liang, Y. F.; Tang, C.; Li, X.; Jiao, N. From simple organobromides or olefins to highly value-added bromohydrins: a versatile performance of dimethyl sulfoxide. Green Chem. 2015, 17 (5), 2727-2731.
Gefahrenhinweise (EU): H227
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