Question

Which of the following is a set of enamine?
I.
                             
II.

III.
                          
IV.

V.

(A) I and II
(B) II, III and IV
(C) II, IV and V
(D) Only II

Answer 1

Hint: An enamine is a compound formed by the condensation of an aldehyde or a ketone with a secondary amine (like pyrrolidine, piperidine, and morpholine). It can act as a good nucleophile as well as a good base. It contains a carbon – nitrogen single bond. These are labile in nature. The α, β-unsaturated amines are known as enamines.

Complete Step by Step Answer:
We have to identify which of the given compounds are α, β-unsaturated amines. The compounds I and V contain carbon-nitrogen double bonds. So, the compounds I and V are not enamines. The compound IV is not an α, β-unsaturated amine. Thus, it is also an enamine. As compound III contains a hydroxyl group. Hence, it is not an enamine.
Only compound II is an α, β-unsaturated amines and contains a carbon-nitrogen single bond. Hence, it is an enamine.
Correct Option: (D) Only II.

Additional Information: The enamines can be used to synthesise β-ketonitriles. It can also react with an acid halide to form β-dicarbonyls. These get reduced to saturated amines by catalytic hydrogenation. The primary and secondary enamines are thermodynamically unstable. It exists in an unfavourable equilibrium with their imine tautomer.

Note: For a compound to be enamine, it is necessary that it should be an α, β-unsaturated amines and must contain a carbon–nitrogen single bond.