Question

Reaction for preparation of primary amine is:
A.Hinsberg reaction
B.Hoffman mustard oil reaction
C.Hoffman bromamide reaction
D.Liberman nitroso reaction

Answer 1

Hint: To answer this question, you must recall the reactions used for the preparation of amines. You need to be familiar with the mechanism and product of all the above given reactions. Primary amines are mostly prepared from chlorides or amides.

Complete step-by-step answer:Considering option A, we have Hinsberg reaction.
Hinsberg reaction is not a reaction for the preparation of amines. It is used as a test to distinguish between primary secondary and tertiary amines. Considering option B, we have Hoffman mustard oil reaction.
This reaction is used for the preparation of isothiocyanates from primary amines by reacting them with alcoholic carbon disulphide and mercuric chloride.
Considering option C, we have Hoffman bromamide reaction.
In this reaction, a primary amide is reacted with an alcoholic or aqueous solution of potassium hydroxide and bromine, it results in the formation of a primary amine having one less carbon atom than the original reactant. It can be used to prepare both aliphatic and aromatic primary amines.

Considering option D, we have Liberman nitroso reaction
In this reaction, a phenol is reacted with sodium nitrite and results in the formation of indophenol.

Thus, the correct answer is C.

Note: In the Hinsberg test, the amine to be identified is shaken with the Hinsberg reagent (benzene sulfonyl chloride) in presence of aqueous solution of an alkali. A primary amine results into the formation of a sulfonamide salt which is soluble in water. On acidification, the salt precipitates. A secondary amine would directly form a precipitate of a sulfonamide salt. A tertiary amine does not show any reaction with Hinsberg reagent.