tautomerism

tau·tom·er·ism

T0061800 (tô-tŏm′ə-rĭz′əm)n. Chemical isomerism characterized by facile interconversion of isomeric forms in equilibrium, especially by migration of a hydrogen atom.

[tauto- + (iso)merism.]

tau′to·mer (tô′tə-mər) n.tau′to·mer′ic (tô′tə-mĕr′ĭk) adj.

tautomerism

(tɔːˈtɒməˌrɪzəm) n (Chemistry) the ability of certain chemical compounds to exist as a mixture of two interconvertible isomers in equilibrium. See also keto-enol tautomerism[C19: from tauto- + isomerism] tautomeric adj

tau•tom•er•ism

(tɔˈtɒm əˌrɪz əm)

n. the ability of certain organic compounds to react in isomeric structures that differ from each other in the position of a hydrogen atom and a double bond. [1880–85; tauto- + (iso) merism] tau`to•mer′ic (-təˈmɛr ɪk) adj.

tautomerism

Tautomerism occurs when a compound exists as two different structural isomers that are in dynamic equilibrium with each other.

Translations

tautomeria

Tautomerism

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.

Tautomerism

rapid, reversible structural isomerization. At equilibrium, substances that can tautomerize are mixtures of two or more interconverting isomers, or tautomers. The most common type of tautomerism is triadic prototropy, which involves the migration of a proton between the end atoms of a triad, or system of three atoms; two of the three atoms are linked by a double bond, which is shifted when the migration occurs. Examples of triadic prototropy are given below. The types shown are the keto-enol (a), imino-enamino (b), and amido (c), including lactim-lac-tam (d), triple-carbon (e), and ring-chain (f) tautomerism:

Dyadic prototropy, that is, tautomerism where proton migration occurs in a system of two atoms, describes the isomerization of hydrocyanic acid and the acids and thio acids of phosphorus. This type of tautomerism is associated with a change in the valence of one of the dyad atoms:

Anionotropy, or tautomerism involving migration of a negatively charged atom or group of atoms, is observed in many allyl halides and allyl alcohols and in their respective derivatives:

Tautomerism can also be encountered in valence isomers—that is, isomers that interconvert through a redistribution of valences between the atoms of the molecule’s skeleton rather than through a migration of substituents. An example is provided by cyclooctatriene, which exists in equilibrium with a bicyclic isomer:

Individual tautomers can sometimes be isolated. In most cases (HCN and others), however, the presence of tautomers is established spectrally.

Many substances form two series of derivatives corresponding to two possible tautomeric forms. As a rule, however, this phenomenon is explained not by tautomerism but by duality in the reactivity (seeRESONANCE). Tautomerism presupposes the existence of tautomers; the existence must be proved in each case.

REFERENCE

Ingold, C. Teoreticheskie osnovy organicheskoi khimii. Moscow, 1973. Page 658. (Translated from English.)

B. L. DIATKIN

tautomerism

[taw-tom´er-izm] stereoisomerism in which the compounds are mutually interconvertible, under normal conditions, forming a mixture that is in dynamic equilibration. adj., adj tautomer´ic.

tau·tom·er·ism

(taw-tom'ĕr-izm), A phenomenon in which a chemical compound exists in two forms of different structure (isomers) in equilibrium, the two forms differing, usually, in the position of a hydrogen atom; for example, keto-enol tautomerism, R-CH₂-C(O)-R' ⇄ R-CH=C(OH)-R'. [G. tautos, the same, + meros, part]

tau·tom·er·ism

(taw-tom'ĕr-izm) A phenomenon in which a chemical compound exists in two forms of different structure (isomers) in equilibrium, the two forms differing, usually, in the position of a hydrogen atom. [G. tautos, the same, + meros, part]

单词	tautomerism
释义	tautomerism tau·tom·er·ism T0061800 (tô-tŏm′ə-rĭz′əm)n. Chemical isomerism characterized by facile interconversion of isomeric forms in equilibrium, especially by migration of a hydrogen atom. [tauto- + (iso)merism.] tau′to·mer (tô′tə-mər) n.tau′to·mer′ic (tô′tə-mĕr′ĭk) adj. tautomerism (tɔːˈtɒməˌrɪzəm) n (Chemistry) the ability of certain chemical compounds to exist as a mixture of two interconvertible isomers in equilibrium. See also keto-enol tautomerism[C19: from tauto- + isomerism] tautomeric adj tau•tom•er•ism (tɔˈtɒm əˌrɪz əm) n. the ability of certain organic compounds to react in isomeric structures that differ from each other in the position of a hydrogen atom and a double bond. [1880–85; tauto- + (iso) merism] tau`to•mer′ic (-təˈmɛr ɪk) adj. tautomerism Tautomerism occurs when a compound exists as two different structural isomers that are in dynamic equilibrium with each other. Translations tautomeria Tautomerism 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. Tautomerism rapid, reversible structural isomerization. At equilibrium, substances that can tautomerize are mixtures of two or more interconverting isomers, or tautomers. The most common type of tautomerism is triadic prototropy, which involves the migration of a proton between the end atoms of a triad, or system of three atoms; two of the three atoms are linked by a double bond, which is shifted when the migration occurs. Examples of triadic prototropy are given below. The types shown are the keto-enol (a), imino-enamino (b), and amido (c), including lactim-lac-tam (d), triple-carbon (e), and ring-chain (f) tautomerism: Dyadic prototropy, that is, tautomerism where proton migration occurs in a system of two atoms, describes the isomerization of hydrocyanic acid and the acids and thio acids of phosphorus. This type of tautomerism is associated with a change in the valence of one of the dyad atoms: Anionotropy, or tautomerism involving migration of a negatively charged atom or group of atoms, is observed in many allyl halides and allyl alcohols and in their respective derivatives: Tautomerism can also be encountered in valence isomers—that is, isomers that interconvert through a redistribution of valences between the atoms of the molecule’s skeleton rather than through a migration of substituents. An example is provided by cyclooctatriene, which exists in equilibrium with a bicyclic isomer: Individual tautomers can sometimes be isolated. In most cases (HCN and others), however, the presence of tautomers is established spectrally. Many substances form two series of derivatives corresponding to two possible tautomeric forms. As a rule, however, this phenomenon is explained not by tautomerism but by duality in the reactivity (seeRESONANCE). Tautomerism presupposes the existence of tautomers; the existence must be proved in each case. REFERENCE Ingold, C. Teoreticheskie osnovy organicheskoi khimii. Moscow, 1973. Page 658. (Translated from English.) B. L. DIATKIN tautomerism tautomerism [taw-tom´er-izm] stereoisomerism in which the compounds are mutually interconvertible, under normal conditions, forming a mixture that is in dynamic equilibration. adj., adj tautomer´ic. tau·tom·er·ism (taw-tom'ĕr-izm), A phenomenon in which a chemical compound exists in two forms of different structure (isomers) in equilibrium, the two forms differing, usually, in the position of a hydrogen atom; for example, keto-enol tautomerism, R-CH₂-C(O)-R' ⇄ R-CH=C(OH)-R'. [G. tautos, the same, + meros, part] tau·tom·er·ism (taw-tom'ĕr-izm) A phenomenon in which a chemical compound exists in two forms of different structure (isomers) in equilibrium, the two forms differing, usually, in the position of a hydrogen atom. [G. tautos, the same, + meros, part]
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