Following is a confirmatory test for aromatic primary amines. Identify reagent (A) and (B)
- (A); (see structure)
- (B); (see structure)
- (C); (see structure)
- (D); (see structure)
Answer: (D)
Solution
The confirmatory test for aromatic primary amines is the azo dye test (coupling reaction).
Step 1: The aromatic primary amine is first converted to a diazonium salt using reagent A:
Reagent A = at 0-5°C (diazotization)
Step 2: The diazonium salt then couples with an electron-rich aromatic compound (reagent B) to form a colored azo dye:
Reagent B = β-naphthol (2-naphthol), which is the most commonly used coupling agent.
The formation of an orange-red azo dye confirms the presence of an aromatic primary amine.
Therefore, option (4) is correct with A = and B = β-naphthol.
Step 1: The aromatic primary amine is first converted to a diazonium salt using reagent A:
Reagent A = at 0-5°C (diazotization)
Step 2: The diazonium salt then couples with an electron-rich aromatic compound (reagent B) to form a colored azo dye:
Reagent B = β-naphthol (2-naphthol), which is the most commonly used coupling agent.
The formation of an orange-red azo dye confirms the presence of an aromatic primary amine.
Therefore, option (4) is correct with A = and B = β-naphthol.
JEE Main · 2024 · 30 Jan 2024 · Shift 1 · Single correct option