Amongst the compounds given, the one that would form a brilliant colored dye on treatment with NaNO2 in dil. HCl followed by addition to an alkaline solution of β-naphthol is
(A)(see structure)
(B)(see structure)
(C)(see structure)✓ Correct
(D)(see structure)
Answer: (C)
Solution
The reaction sequence describes the formation of an azo dye via diazotization followed by coupling with β-naphthol.
For diazotization, a primary aromatic amine is required. The amine reacts with NaNO2 in dil. HCl to form a diazonium salt, which then couples with β-naphthol in alkaline medium to form a colored azo dye.
Option (A) is a tertiary amine (N,N-dimethylaniline) — cannot form diazonium salt. Option (B) is a secondary amine (N-methylaniline) — cannot form stable diazonium salt. Option (C) is a primary aromatic amine (p-toluidine) — can undergo diazotization and coupling. Option (D) is a primary aliphatic amine (benzylamine) — aliphatic diazonium salts are unstable.
Therefore, option (C) is correct.
JEE Advanced · 2011 · 10 Apr 2011 · Paper 2 · Single correct option
