The organic compound (X) boiled with water gives phenol. What is the compound (X) ? a) Chlorobenzene b) Benzenediazonium chloride c) Benzenesulphonic d) Aniline

The organic compound (X) that boils with water to give phenol is benzenediazonium chloride.

C₆H₅N₂+ Cl−benzenediazonium chlorideH₂O, heat (boiling)phenolphenol+N₂

When benzenediazonium chloride ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{N}{}_2{}^{+}\mathrm{Cl}{}^{-}$) is heated with water, it undergoes hydrolysis to form phenol ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{OH}$) via a diazonium intermediate. This reaction is known as the diazotization followed by hydrolysis process. The mechanism involves the replacement of the diazonium group ($-\mathrm{N}{}_2{}^{+}$) with a hydroxyl group ($-\mathrm{OH}$) in the presence of water.

The other options are incorrect because:

• Chlorobenzene ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{Cl}$) does not hydrolyze to phenol under boiling water.
• Benzenesulphonic acid ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{SO}{}_3\mathrm{H}$) requires strong acid or fusion with NaOH, not just boiling water.
• Aniline ($\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{NH}{}_2$) does not convert to phenol under these conditions.

Chlorobenzene (no reaction with water)Chlorobenzene (no reaction with water)Benzenesulphonic acid (requires strong conditions)Benzenesulphonic acid (requires strong conditions)Aniline (no conversion to phenol under these conditions)Aniline (no conversion to phenol under these conditions)

Thus, the correct answer is (b) Benzenediazonium chloride.