tautomerism

tau·tom·er·ism

noun \tȯ-ˈtä-mə-ˌri-zəm\

Definition of TAUTOMERISM

: isomerism in which the isomers change into one another with great ease so that they ordinarily exist together in equilibrium

First Known Use of TAUTOMERISM

circa 1890

tau·tom·er·ism

noun \tȯ-ˈtäm-ə-ˌriz-əm\   (Medical Dictionary)

Medical Definition of TAUTOMERISM

: isomerism in which the isomers change into one another with great ease so that they ordinarily exist together in equilibrium

tautomerism

noun    (Concise Encyclopedia)

Existence 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 (CHCO; see functional group) moves to the oxygen atom, making it an enol group (CCOH). 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.