Keto-Enol Tautomerism

Keto-enol tautomerism is the process of interconversion between keto and enol forms of organic compounds. The keto form is characterized by a carbonyl group (C=O), while the enol form has a carbon-carbon double bond (C=C) and an alcohol group (-OH). This tautomerism is common in compounds containing alpha-hydrogen atoms that can easily undergo deprotonation and form enolate ions.

Compounds Exhibiting Keto-Enol Tautomerism

1. C6H5COH (benzaldehyde)
Benzaldehyde exhibits keto-enol tautomerism because it contains an alpha-hydrogen atom adjacent to the carbonyl group. The keto form of benzaldehyde is more stable than the enol form, but the latter can be observed in the presence of a base catalyst.

2. C6H5COCH3 (acetophenone)
Acetophenone also exhibits keto-enol tautomerism because it contains an alpha-hydrogen atom adjacent to the carbonyl group. However, the keto form of acetophenone is more stable than the enol form, and the latter is only observed in the presence of a strong base or acid catalyst.

3. C6H5COC6H5 (dibenzoylmethane)
Dibenzoylmethane exhibits keto-enol tautomerism because it contains two alpha-hydrogen atoms adjacent to the carbonyl groups. The keto form of dibenzoylmethane is more stable than the enol form, but the latter can be observed in the presence of a base catalyst.

4. C6H5COCH2COCH3 (pentan-2-one)
Pentan-2-one exhibits keto-enol tautomerism because it contains an alpha-hydrogen atom adjacent to each of the carbonyl groups. The keto form of pentan-2-one is more stable than the enol form, but the latter can be observed in the presence of a base catalyst.

Conclusion

In summary, keto-enol tautomerism is a common process in organic compounds containing alpha-hydrogen atoms adjacent to carbonyl groups. The stability of the keto and enol forms depends on the nature of the substituents and the presence of catalysts. The compounds that exhibit keto-enol tautomerism include benzaldehyde, acetophenone, dibenzoylmethane, and pentan-2-one.

In 2 and 4 option alpha H is present