Identify compound (Z) in the following reaction sequence.

Solution

Chemistry ma’am · 4 steps

Chlorobenzene becomes phenol here, and conc. nitric acid then loads phenol with three nitro groups.

1. Forming X. Aryl halides resist substitution, so OH⁻ can replace Cl only under harsh conditions: 623 K and 300 atm (the Dow process). In this much NaOH, the product is sodium phenoxide, C₆H₅ONa. That is X.
2. Forming Y. HCl protonates the phenoxide ion, giving phenol, C₆H₅OH. That is Y.

   C₆H₅OH + 3HNO₃ →(conc.) C₆H₂(NO₂)₃OH + 3H₂O

3. Forming Z. The -OH group strongly activates the ring at the ortho and para positions. With concentrated HNO₃, nitration goes on until both ortho positions and the para position all carry NO₂. The product is 2,4,6-trinitrophenol, called picric acid.
4. So. Z is picric acid, the phenol with NO₂ groups at positions 2, 4 and 6. That is option (b).

The idea to keep. For phenol, the strength of the nitric acid decides the product. Dilute HNO₃ gives a mixture of o- and p-nitrophenol. Concentrated HNO₃ gives 2,4,6-trinitrophenol, picric acid.

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