Explain tautomerism with an example.

Tautomerism is a chemical phenomenon where isomers of a compound rapidly interconvert into each other. These isomers are called tautomers. Tautomers have the same molecular formula but differ in the arrangement of atoms and the location of double bonds and/or hydrogen atoms.

An example of tautomerism is found in the molecule keto-enol tautomerism of aldehydes and ketones. Let's take the example of acetone, a simple ketone:

Keto form (Acetone): In its stable form, acetone exists predominantly as a keto tautomer. In this form, the carbon-oxygen double bond is located between the second and third carbon atoms.
CH
3
−
C
(
O
)
−
CH
3
CH
3
​
−C(O)−CH
3
​

Enol form (Enolized Acetone): Under certain conditions, acetone can tautomerize to its enol form. In the enol form, one of the hydrogen atoms on a neighboring carbon migrates to form a double bond with the carbon atom bearing the oxygen.
CH
3
−
C
(
OH
)
=
CH
2
CH
3
​
−C(OH)=CH
2
​

This rapid interconversion between the keto and enol forms of acetone is an example of tautomerism. Tautomers may have different chemical properties, such as acidity or reactivity, and this phenomenon is crucial in understanding various organic reactions.