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Keto-enol tautomerism is the existence of chemical equilibrium among the keto form and enol form of a compound.

It is the reaction in which the isomerization or interconversion occurs between ketone and enol molecules in the presence of an acid or base. The enol and ketone are tautomers of each other.

Simple keto-enol tautomerism can be represented as shown below:

Keto-enol tautomerism

An enol tautomer will have an OH group attached to $\mathrm{C}=\mathrm{C}$, whereas the keto tautomer has$\mathrm{C}=\mathrm{O}$ and an additional bond.

The conversion to enol form from keto form can be represented as shown below:

Interconversion of keto-enol form

The interconversion of keto-enol form can be represented as shown below:

Keto-enol interconversion