Question

The order of reactivity of phenol (1), nitrobenzene (2), and benzene (3) towards nitration is:
A. (3) > (1), > (2)
B. (2) > (3) > (1)
C. (1) > (3) > (2)
D. (1) > (2) > (3)

Answer 1

Nitration reaction is defined as the reaction where the reactant is treated with nitric acid and sulphuric acid and as result nitro ion or group is attached to the substituent. The nitronium ion is formed by the protonation of nitric acid in the presence of sulphuric acid. It is a type of electrophilic aromatic substitution reaction which depends on the ring activating groups.

Complete step by step answer:
The nitration reaction is a type of electrophilic aromatic substitution reaction where the attachment of the nitro group takes place in the benzene ring. The nitronium ion $NO_2^ +$ acts as the electrophile in this reaction where the nitronium ion is formed by the protonation of nitric acid by the sulphuric acid.
The electrophilic substitution reaction is defined as the reaction where the electrophilic group is added to the benzene ring. In this reaction the C-H bond is broken and C-E bond is formed where E is the electrophile.
The rate of nitration depends on the ring activating groups attached to the benzene ring. The ring activating groups are those which can donate their lone pairs and the ring deactivation groups are those which take electrons. The phenol contains a hydroxyl group attached to a benzene ring, the oxygen of the hydroxyl group contains lone pairs which it can donate. So it is a ring activating group. In nitro benzene, the nitro group is attached to the benzene ring which is a ring deactivating group.
In benzene, no group is attached so it is neither ring activation nor ring deactivating.
Thus, the reactivity of phenol will be higher than benzene and the nitrobenzene will be least reactive.
The order is shown below.
Phenol > benzene > nitrobenzene
(1) > (3) > (2)
Therefore, the correct option is C.

Note: The ring activation group shows +I inductive effect and +R resonance affect. The resonance effect is also known as mesomeric effect.