tautomer

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tautomer

(tô`təmər), one of two or more structural isomersisomer
, in chemistry, one of two or more compounds having the same molecular formula but different structures (arrangements of atoms in the molecule). Isomerism is the occurrence of such compounds. Isomerism was first recognized by J. J. Berzelius in 1827.
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 that exist in equilibrium and are readily converted from one isomeric form to another. Of the various types of tautomerism that are possible, two are commonly observed. In keto-enol tautomerism a simultaneous shift of electrons and a hydrogen atom occurs; it was first observed by K. Meyer in the ethyl ester of 3-oxobutanoic acid (ethyl acetoacetate), which occurs naturally as a mixture of the two forms. Ring-chain tautomerism, first recognized by Emil Fischer, is exhibited by glucose. It arises as a result of the aldehyde group (-CHO) in a sugar chain molecule reacting with one of the hydroxy groups (-OH) in the same molecule to give it a cyclic (ring-shaped) form.
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Key words: enol/keto; tautomerization; hydantoin; cyclohexanone.
It is well established that acrolein, especially, is difficult to quantify by HPLC due to the complex derivatization of acrolein because of tautomerization of its hydrazone in the acidic DNPH solution [3].
Water catalysed tautomerization has been studied by experimental [27] and computational methods [28, 29].
Aman et al., "The immunoregulatory mediator macrophage migration inhibitory factor (MIF) catalyzes a tautomerization reaction," Molecular Medicine, vol.
Moreno, Efficient Tautomerization Hydrazone-Azomethine Imine under Microwave Irradiation.
Two of these molecules couple by C--O coupling, followed by tautomerization to create a dimer.
Absorption spectra of the dyes 3a-3f were taken in pure chloroform and chloroform/DMF mixtures of 80/20, 60/40, 40/60, 20/80 (v/v), and pure DMF to understand whether the bathochromic shift results from tautomerization or ionization in basic chloroform solution (Table 6).
Regarding influences that involve sugar chemistry, oxygenated free radicals which resulted in early glycation stages have been proven to be contributors to glycoxidative damage: glycolaldehyde that results in the initial stages of nonenzymatic glycosylation is noncyclizable and may undergo tautomerization, yielding enediols that are easily subject to autooxidation.
Assignment of this band is also considered to be due to the [alpha] [beta]-unsaturated and [beta]-imino nitrile groups arising from the occurrence of dehydrogenation reactions or from tautomerization and isomerization of the ladder-like structure [65, 66].
It was demonstrated that in many ortho-hydroxylated Schiff bases, the tautomerization equilibrium between enol-imine form (N *** H-O) and keto-enamine form (N-H *** O) occurred in the excited states of intramolecularly H-bonded molecule with effect on the [pi]-electron configuration.
In the presence of hydrogen donor, the mesomerism of the peptide linkage, which is the tautomerization form of the interaction in PVP as shown in Fig.