JEE Main · 2011 · 10 Apr 2011 · Offline · General Organic Chemistry

Identify the compound that exhibits tautomerism.

(A)Lactic acid
(B)2-Pentanone✓ Correct
(C)Phenol
(D)2- Butene

Answer: (B)

Solution

Keto-enol tautomerism needs an

α

-hydrogen next to a carbonyl, so that a hydrogen can shift and a double bond migrate between the keto and enol forms. 2-Pentanone,

C H_{3} COC H_{2} C H_{2} C H_{3}

, has

α

-hydrogens on either side of its carbonyl and sits in a keto-enol equilibrium. Lactic acid, phenol and 2-butene do not show the ordinary keto-enol tautomerism of a ketone, so the compound that exhibits tautomerism is 2-pentanone.

JEE Main · 2011 · 10 Apr 2011 · Offline · Single correct option

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