Q74 / 240 · KCET 2026 · Chemistry
The compound from which chlorobenzene cannot be prepared easily is
- AAniline
- BBenzene
- Correct answerCPhenol
- DBenzene diazonium chloride
Solution
Chlorobenzene can be easily prepared from aniline by first converting it to benzene diazonium chloride, followed by the Sandmeyer reaction.
Chlorobenzene can be easily prepared from benzene by electrophilic aromatic substitution using $Cl_2$ in the presence of a Lewis acid catalyst like $FeCl_3$ or $AlCl_3$.
Chlorobenzene can be easily prepared from benzene diazonium chloride by treating it with $Cu_2Cl_2$ and $HCl$ (Sandmeyer reaction).
In phenol, the carbon-oxygen bond acquires a partial double bond character due to resonance between the lone pairs on oxygen and the benzene ring. This makes the $C-O$ bond stronger and difficult to cleave. Therefore, nucleophilic substitution of the hydroxyl group by a chloride ion (using reagents like $PCl_5$ or $SOCl_2$) is very difficult, and chlorobenzene cannot be prepared easily from phenol.
Answer: Phenol
Chlorobenzene can be easily prepared from benzene by electrophilic aromatic substitution using $Cl_2$ in the presence of a Lewis acid catalyst like $FeCl_3$ or $AlCl_3$.
Chlorobenzene can be easily prepared from benzene diazonium chloride by treating it with $Cu_2Cl_2$ and $HCl$ (Sandmeyer reaction).
In phenol, the carbon-oxygen bond acquires a partial double bond character due to resonance between the lone pairs on oxygen and the benzene ring. This makes the $C-O$ bond stronger and difficult to cleave. Therefore, nucleophilic substitution of the hydroxyl group by a chloride ion (using reagents like $PCl_5$ or $SOCl_2$) is very difficult, and chlorobenzene cannot be prepared easily from phenol.
Answer: Phenol
Hence, the correct answer is option: 'C'.