Match List I with List II:
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 3 steps

Each reagent swaps the -N₂⁺ group for one partner, except aniline, which keeps the N=N and couples.

1. Two kinds of reaction. Benzenediazonium chloride either loses N₂, so a new group takes its place on the ring, or keeps both nitrogens and couples with another ring to give an azo compound. Only aniline gives the second kind.

   Reagent	Reaction	Product
   A. Aniline	Coupling at the para position of aniline, N=N kept	III. p-aminoazobenzene
   B. HBF₄, Δ	Balz–Schiemann: ArN₂⁺BF₄⁻ is heated and gives off N₂ and BF₃	I. Fluorobenzene
   C. Cu, HCl	Gattermann reaction, -N₂⁺ replaced by -Cl	IV. Chlorobenzene
   D. CuCN/KCN	Sandmeyer reaction, -N₂⁺ replaced by -CN	II. Benzonitrile

2. Read the partner. In each replacement, the group that enters the ring comes from the reagent: F from HBF₄, Cl from HCl, CN from KCN. Copper only helps the reaction along.
3. So. A-III, B-I, C-IV, D-II, which is option (a).

The idea to keep. In diazonium replacements, ask which anion the reagent brings: that is the group that lands on the ring. Only an activated arene such as aniline or phenol keeps the N=N and gives an azo dye.

Answer from the NTA final answer key. Solution by PrepWiser.