Question

Write the order of reactivity and explain why of:
Benzene, Aniline, Nitrobenzene

Answer 1

Dear Student,

The increasing order for reactivity is :
Nitrobenzene < Benzene < Aniline

The presence of electron withdrawing group deactivates the ring while the present of electron releasing groups activates the ring.The activation or deactivation of the benzene ring toward electrophilic substitution may be corelates with electron donating or electron withdrawing influence of the substituents. Inductive effect and resonance effect both play a key role here.
The group showing -I effect deactivates the ring by withdrawing electrons from the benzene ring while the group showing +I effect activates the ring by giving electrons to the benzene ring. Also, resonance facilitates electron donation or withdrawal. The groups showing -R effect deactivates the ring wile +R effect groups activates the ring.

NO₂ shows -I as well as -R effect and so is unreactive. Benzene has no such effects while NH₂ shows +R and +I effect thereby activating the ring.