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Tautomers are constitutional isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond. The concept of tautomerizations is called tautomerism. Because of the rapid interconversion, tautomers are generally considered to be the same chemical compound. Tautomerism is a special case of structural isomerism and can play an important role in non-canonical base pairing in DNA and especially RNA molecules. == Chemistry == In solutions in which tautomerization is possible, a chemical equilibrium of the tautomers will be reached. The exact ratio of the tautomers depends on several factors, including temperature, solvent, and pH.〔 〕 Common tautomeric pairs include: * ketone - enol, e.g., for acetone (see: keto–enol tautomerism); * enamine - imine; * ketene - ynol, e.g., for ethenone; * nitroso - oxime; * amide - imidic acid, e.g., during nitrile hydrolysis reactions; * lactam - lactim, an amide-imidic acid tautomerism in heterocyclic rings, e.g., in the nucleobases guanine, thymine, and cytosine; * enamine - enamine, e.g., during pyridoxalphosphate-catalyzed enzymatic reactions; and * anomers of reducing sugars in solution, which interconvert through an intermediate open chain form. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tautomer」の詳細全文を読む スポンサード リンク
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