Give one chemical test to distinguish between the following pairs of compounds. (i) Methylamine and dimethylamine (ii) Secondary and tertiary amines (iii) Ethylamine and aniline (iv) Aniline and benzylamine (v) Aniline and N-methylaniline.
Carbylamine reaction: When heated with chloroform and alcoholic KOH, methylamine (primary amine) gives an offensive smelling isocyanide (carbylamine), while dimethylamine (secondary amine) does not give this reaction.
Hinsberg test using benzene sulfonyl chloride: Secondary amines form sulfonamide which is insoluble in alkali, whereas tertiary amines do not react with benzene sulfonyl chloride.
Diazotisation test: Treat with NaNO₂ and HCl at 0-5°C. Aniline (aromatic amine) forms diazonium salt which gives orange azo dye with phenol. Ethylamine (aliphatic amine) does not form stable diazonium salt.
Diazotisation test: Aniline forms diazonium salt with NaNO₂/HCl which undergoes coupling reaction with phenol to give orange dye. Benzylamine does not form diazonium salt as the amino group is not directly attached to aromatic ring.
Carbylamine reaction: Aniline (primary amine) gives offensive smelling isocyanide when heated with chloroform and alcoholic KOH. N-methylaniline (secondary amine) does not respond to this test.
Explanation
The context mentions Carbylamine reaction and Diazotisation as key topics (Question 9.7). Carbylamine reaction is specific to primary amines, distinguishing them from secondary/tertiary amines. Diazotisation is applicable to aromatic primary amines (arylamines) as stated: 'Aryldiazonium salts, usually obtained from arylamines.' The coupling reaction of aryldiazonium salts with phenols forms azo dyes, providing a visual test. For secondary vs tertiary amines, Question 9.6 asks about identification methods, with Hinsberg test being the standard NCERT approach.