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tautomerism |
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tautomerismExistence of two or more chemical compounds that have the same chemical composition but different structures (isomers) and that convert easily from one to another. A major class of tautomeric reactions involves exchange of a hydrogen atom between two other atoms in the same molecule, in both cases forming a covalent bond. For example, in keto-enol tautomerism, the hydrogen atom bonded to the carbon atom in a carbonyl (keto) group (−CH−C=O; see functional group) moves to the oxygen atom, making it an enol group (−C=C−OH). The keto form predominates in many aldehydes and ketones, the enol form in phenols. Sugars (e.g., glucose) exhibit tautomerism between open (chain) forms and closed (ring) forms. See also isomerism. tautomerism [tȯ′täm·ə‚riz·əm] (chemistry) The reversible interconversion of structural isomers of organic chemical compounds; such interconversions usually involve transfer of a proton. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Because of tautomerism (hydrogen shifts within the molecule), xanthines such as caffeine appear to have phenolic structure, but the preferred chemical structure in xanthines is the ketone. |
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