Question

Products A and B formed in the following reactions are respectively :

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Sulphanilic acid (as its ammonium acetate salt) is diazotised by \(\mathrm{HNO_2}\) to the diazonium acetate, which then couples with aniline at the para position of the aniline ring.

Answer 1

The Correct Option is D

The stem shows the ammonium acetate salt of \(p\)-aminobenzenesulphonic acid treated with \(\mathrm{HNO_2}\). The primary aromatic amine is diazotised to the diazonium acetate, \(\mathrm{Ar{-}N_2^+\,CH_3COO^-}\) (\(\mathrm{Ar} = 4\text{-}\mathrm{HO_3S{-}C_6H_4}\)), drawn in options (3) and (4) as \(\mathrm{Ar{-}N{=}N{-}O{-}C(=O)CH_3}\) (A).
With aniline (\(\mathrm{C_6H_5NH_2}\)) the diazonium ion acts as an electrophile and couples at the para position of the aniline ring (azo coupling), giving \(\mathrm{Ar{-}N{=}N{-}C_6H_4{-}NH_2}\) (B), the aminoazo dye.
Options (1) and (2) show an acyl azo compound \(\mathrm{Ar{-}N{=}N{-}COCH_3}\) for A, which is not formed; option (3) shows a triazene \(\mathrm{Ar{-}N{=}N{-}NH{-}Ph}\) for B (N-coupling), which is not the major product. Option (4) fits A and B.
Answer: (4)