1) Enol 
A structure formed by facile motion of a hydrogen from one site to another within the same molecule.
Tautomers are constitutional isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond. The concept of tautomerizations is called tautomerism. Because of ...
(taw´to-mәr) a chemical compound exhibiting, or capable of exhibiting, tautomerism.
A structure formed by facile motion of a hydrogen from one site to another within the same molecule. See also: Hydrogen.