Question

Cyclohexylamine and aniline can be distinguished by

• A. Hinsberg's test
• B. Carbylamine test
• C. Bromine test
• D. Beilstein's test
• E. Lassaigne's test

Hint:

While aniline and aliphatic primary amines share many amine-group reactions, the presence of the aromatic ring in aniline allows for unique substitution reactions like bromination or azo-dye formation.

Answer 1

The Correct Option is C

Concept: Differentiation between aliphatic amines (cyclohexylamine) and aromatic amines (aniline) relies on the reactivity of the aromatic ring. Aniline is highly activated toward electrophilic aromatic substitution.

Step 1: {Evaluate shared reactions.} Both cyclohexylamine and aniline are primary amines. Therefore, both will give positive results for the Hinsberg's test and the Carbylamine test.

Step 2: {Reactivity with Bromine water.} Aniline has a benzene ring highly activated by the $-NH_2$ group. It reacts rapidly with bromine water ($Br_2/H_2O$) to form a white precipitate of 2,4,6-tribromoaniline.

Step 3: {Contrast with cyclohexylamine.} Cyclohexylamine is an aliphatic amine and does not possess a benzene ring. It does not react with bromine water to form a precipitate, providing a clear visual distinction.