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.
References in periodicals archive ?
Tautomerization of the hemiacetal form is responsible for the ring opening which results in the formation of cis-chalcones then undergoing further isomerization to trans-chalcones (pH 2-7).
It was suggested that frst ALA enol form is generated by tautomerization.
It is now believed that the interconversion actually occurs by tautomerization of an enamine intermediate formed during the transamination of t-(+)-isoleucine (17-19).
Lupia, the material dissipates incident energy by photo tautomerization and vibrational relaxation.
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.