Demethylation - wikipedia Demethylation Demethylation is the chemical process resulting in the removal of a methyl group ( CH ) from a molecule. A common way of demethylation is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms. The counterpart of demethylation is methylation. Contents 1 In biochemistry 2 In organic chemistry 2.1 O - Demethylation 2.2 N - Demethylation 3 References 4 See also In biochemistry In biochemical systems, the process of demethylation is catalyzed by demethylases. These enzymes oxidize N - methyl groups, which occur in histones and some forms of DNA : R N - CH + O → R N-H + CH O One such oxidative enzyme family is the cytochrome P450. Alpha - ketoglutarate - dependent hydroxylases are active for demethylation of DNA, operating by similar pathway. These reactions exploit the weak C-H bond adjacent to amines. In organic Chemistry O - demethylation Demethylation typically refers to cleavage of ethers, especially aryl ethers, although there are some exceptions, for instance cf. `` desipramine ''. Apparently, aryl ethers are pervasive in lignin - derived compounds. The reaction typically requires harsh conditions or harsh reagents. For example, the methyl ether in vanillin can be removed by heating near 250 ° C with strong base. Stronger nucleophiles such as diorganophosphides ( LiPPh ) also cleave aryl ethers under milder conditions. Boron tribromide is a classical reagent for the dealkylation of methyl arylethers. The mechanism of ether dealkylation proceeds via the formation of a complex between the boron center and the ether oxygen followed by the elimination of an alkyl bromide to yield a dibromo ( organo ) borane. The dibromo ( organo ) borane can then undergo hydrolysis to give the alcohol or phenol, boric acid, and hydrogen bromide as products. ROR + BBr → RO ( BBr ) R RO ( BBr ) R → ROBBr + RBr ROBBr + 3 H O → ROH + B ( OH ) + 2 HBr Methyl esters also are susceptible to demethylation, which is usually achieved by saponification. Highly specialized demethylations are abundant such as the Krapcho decarboxylation : N - Demethylation N - demethylation of 3 ° amines is by the von Braun reaction, which uses BrCN as the reagent to give the corresponding nor - derivatives. A modern variation of the Von Braun reaction was developed where BrCN was superseded by ethyl chloroformate. The preparation of Paxil from arecoline is an application of this reaction, as well as the synthesis of GSK - 372,475, for example. References Jump up ^ Clayden, J. ; Greeves, N. ; Warren, S. ; Wothers, P. ( 2001 ). Organic Chemistry. Oxford, Oxfordshire : Oxford University Press. ISBN 0 - 19 - 850346 - 6. Jump up ^ Smith, Michael B. ; March, Jerry ( 2007 ), Advanced Organic Chemistry : Reactions, Mechanisms, and Structure ( 6th ed. ), New York : Wiley - Interscience, ISBN 0 - 471 - 72091 - 7 Jump up ^ Roland Sigel ; Sigel, Astrid ; Sigel, Helmut ( 2007 ). The Ubiquitous Roles of Cytochrome P450 Proteins : Metal Ions in Life Sciences. New York : Wiley. ISBN 0 - 470 - 01672 - 8. Jump up ^ Irwin A. Pearl ( 1949 ). `` Protocatechulic Acid ''. Organic Syntheses. 29 : 85. ; Collective Volume, 3, p. 745 Jump up ^ Robert E. Ireland and David M. Walba ( 1977 ). `` Demethylation of Methyl Aryl Ethers : 4 - Ethoxy - 3 - hydroxybenzaldehyde ''. Organic Syntheses. 56 : 44. ; Collective Volume, 3, p. 745 Jump up ^ J.F.W. McOmie, D.E. West ( 1969 ). `` 3, 3 ' - Dihydroxybiphenyl ''. Organic Syntheses. 49 : 13. ; Collective Volume, 5, p. 412 See also Methylation, the addition of a methyl group to a substrate Retrieved from `` https://en.wikipedia.org/w/index.php?title=Demethylation&oldid=824472599 '' Categories : Gene expression Organic reactions Hidden categories : All articles with unsourced statements Articles with unsourced statements from February 2015 Talk Contents About Wikipedia Bosanski Català Deutsch Eesti Español Nederlands 日本 語 Português Српски / srpski Srpskohrvatski / српскохрватски Suomi தமிழ் Українська 中文 Edit links This page was last edited on 7 February 2018, at 15 : 39. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: how to remove a methyl group from benzene
Answer: replacement of a methyl group by a hydrogen atom