NEET 2016 Phase 1 · ChemistryPrevious Year Question

The correct statement regarding a carbonyl compound having a hydrogen atom on its alpha-carbon is:

Answer: (D) A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism.. \textbf{Answer:} (d) keto-enol tautomerism \textbf{Solution:} A carbonyl compound bearing an alpha-hydrogen is in dynamic equilibrium with its enol form.

A.A carbonyl compound with a hydrogen atom on its alpha-carbon never equilibrates with its corresponding enol.
B.A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as aldehyde-ketone equilibration.
C.A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as carbonylation.
D.A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism.✓

Correct Answer

(D) A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism.

Solution & Explanation

\textbf{Answer:} (d) keto-enol tautomerism \textbf{Solution:} A carbonyl compound bearing an alpha-hydrogen is in dynamic equilibrium with its enol form. The alpha-H shifts to the carbonyl oxygen while the $C = O$ becomes $C - OH$ and a new $C = C$ forms: $R - CH X_{2} - CO - R X^{'} R - CH = C (OH) - R X^{'}$ . This interconversion between the keto and enol constitutional isomers is called keto-enol tautomerism. Hence (d).

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