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Eliminations are base-catalyzed reactions in which two atoms or groups are removed or eliminated, usually from one or two carbon atoms. A double bond is frequently formed as the result of this elimination.

The pyrolysis of t-amine oxides (Cope elimination) in dry DMSO proceeds at a convenient rate at 25°C to give 80- 90% yields of olefins. Temperatures of 132-138°C are usually required in water. In addition, the rates in DMSO are 10,000 times faster than in water [Cram, D. J.; Sahyun, M. R. V.; Knox, G. R., J. Am. Chem. Soc. 84, 1734-1735 (1962)].

elimination dmso formula

The rate is higher in wet DMSO than in dry THF because DMSO acts as an internal drying agent and competes with amine oxide for the water present [Sahyun, M. R. V.; Cram, D. J., J. Am. Chem. Soc. 85, 1263-1268 (1963)].

Pure olefins from their dibromides can be obtained by using sodium thiosulfate in DMSO as the debrominating agent. Thus, stilbene dibromide yields stilbene [Ibne-Rasa, K. M.; Tahir, A. R.; Rahman, A., Chem. Ind. (London) 232 (1973)].

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