Question

How will you obtain the following from Chlorobenzene? (Write only chemical equations) (i) Picric Acid
(ii) Dichlorobenzene
(iii) Chlorobenzene Sulphonic Acid

Hint:

Electrophilic substitution reactions of chlorobenzene give nitro, chloro, and sulpho derivatives depending on the reagents used.

Answer 1

(i) Chlorobenzene to Picric Acid:
\[ C_6H_5Cl \; \xrightarrow{Conc. HNO_3 / Conc. H_2SO_4} \; O_2N\!-\!C_6H_4Cl \; \xrightarrow{Further \; Nitration} \; (NO_2)_3C_6H_2OH \; \text{(Picric Acid)} \] (ii) Chlorobenzene to Dichlorobenzene:
\[ C_6H_5Cl \; \xrightarrow{Cl_2 / FeCl_3} \; C_6H_4Cl_2 \; \text{(o- and p-dichlorobenzene)} \] (iii) Chlorobenzene to Chlorobenzene Sulphonic Acid:
\[ C_6H_5Cl \; \xrightarrow{Conc. H_2SO_4, \; Heat} \; ClC_6H_4SO_3H \] Conclusion:
Chlorobenzene undergoes nitration to give picric acid, halogenation to give dichlorobenzene, and sulphonation to give chlorobenzene sulphonic acid.