Question

Convert chlorobenzene to p- chloronitrobenzene.

Answer 1

Hint: The reaction of chlorobenzene to p- chloronitrobenzene is an electrophilic substitution reaction in which a nitro group is substituted on a benzene ring.
The first step would be the generation of electrophile i.e. nitronium ion. Then this nitronium ion will get substituted on the benzene ring.

Complete step by step answer :
The benzene is an aromatic compound. It is stabilised because of resonance. It does not undergo addition reactions because if it does, then the resonance of the ring is disturbed and it gets destabilised. Thus, it undergoes electrophilic substitution reaction.
The reaction of chlorobenzene to p- chloronitrobenzene is an electrophilic substitution reaction in which a nitro group is substituted on a benzene ring.
The electrophile is nitronium ion. The reaction takes place in two steps.
Step 1 : This step involves the generation of electrophile that is nitronium ion. The sulphuric acid and nitric acid react to form nitronium ion and some other products. The reaction is as-
$2{H_2}S{O_4} + HN{O_3} \to \oplus N{O_2} + 2HSO_4^ - + {H_3}O $
Step 2 : This step involves the attack of benzene on nitronium ion to give para products. The resonance is disturbed initially but later on after removal of proton, the resonance is restored. So, one gets a para-substituted product. The reaction is written as -

Note: The Chlorine is an ortho para directing group. This means that it directs the incoming group to ortho and para positions. The nitrogen atom in nitronium ion has positive charge. So, it will make it more reactive towards electrophilic substitution reaction.