Question

Which of the following is an enamine?
i)

ii)

iii)

iv)

v)

(A) i
(B) ii
(C) iii
(D) iv
(E) v

Answer 1

Hint :Enamine has a specific structure, if a compound has the same structure as the general structure of enamine, it can be called as enamine. In an enamine, the nitrogen is attached to the primary carbon with a single bond only.

Complete Step By Step Answer:
The correct answer to this question is option B.
Enamine is a compound in which there exists a carbon atom which is attached to nitrogen with a single bone, and that primary carbon atom is attached to another carbon atom with a double bond. The primary carbon atom is unsaturated.
The general formula of an enamine is shown below
 

In any enamine, there has to be a nitrogen which is attached to the primary carbon with single bond only and primary carbon attached to secondary with double bond only. If any of these conditions are not satisfied, then it cannot be called an enamine.
Further, there can be any kind of groups attached to the remaining valences of carbon and nitrogen atoms. In the above shown figure, the groups of R represent such different groups.
If we look at the options, in the first option, nitrogen is attached to carbon with double bond, in third option primary carbon is attached to secondary carbon with single bond, in fourth option nitrogen is attached to carbon with double bond and also primary carbon is attached to secondary carbon with single bond and same goes with option five.
Hence, according to this formula, the compound shown in option B is an enzyme.

Note :
It is necessary to check every option with the conditions. It is not mandatory that the alkyl groups attached to the secondary carbon are different or separate. For example, in this question, the alkyl group attached to secondary carbon closes with that of the primary carbon making it a hexane ring.