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Tautomers are structural isomers of chemical compounds that readily interconvert in an acidic or a basic medium in the presence of water. The process of conversion of one tautomer into another is known as tautomerization.One such example is keto-enol tautomers.

Enol and keto forms are tautomers that are present in the carbonyl group and differ in the position of a double bond and a proton. They are constitutional isomers that are found to be in equilibrium with each other.

Generally, the keto form is found to be more stable than the enol form. This is due to the reason that C=O is a stronger bond than C=C.

The enol or keto tautomer(s) of each compound is shown below.

Keto-enol forms of compound a

Keto-enol forms of compound b

Keto-enol forms of compound c

Keto-enol forms of compound d

Keto-enol forms of compound e

Keto-enol forms of compound f