The product A formed in the following reaction is

Solution

Chemistry ma’am · 3 steps

Two stages here: first turn -NH₂ into -N₂⁺, then let CuCl swap that N₂ for Cl.

1. Diazotisation. NaNO₂ and HCl give nitrous acid. At 0 °C it converts aniline into benzenediazonium chloride, C₆H₅N₂⁺Cl⁻. The cold keeps this salt from breaking down.
2. Sandmeyer reaction. Cu₂Cl₂, which is CuCl, replaces the -N₂⁺ group with Cl. Nitrogen gas leaves, and the Cl takes the exact ring position where the NH₂ group was.

   C₆H₅NH₂ →(NaNO₂, HCl, 0 °C) C₆H₅N₂⁺Cl⁻ →(Cu₂Cl₂) C₆H₅Cl + N₂ ↑

3. So. A is chlorobenzene, C₆H₅Cl, with one Cl on the ring and no nitrogen left. That is option (c).

The idea to keep. In a Sandmeyer reaction the diazonium group is swapped out. The new group sits exactly where NH₂ was, and the nitrogen is lost as N₂ gas.

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