Assertion (A): Aniline does not undergo the Friedel-Crafts reaction.
Reason (R): The Friedel-Crafts reaction is an electrophilic substitution reaction.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are true but (R) is not the correct explanation of (A).
Assertion (A): Aniline does not undergo the Friedel-Crafts reaction. — True. The –NH2 group of aniline is a Lewis base and forms a salt with aluminium chloride, the Lewis acid catalyst, so alkylation and acylation do not take place.
Reason (R): The Friedel-Crafts reaction is an electrophilic substitution reaction. — True. An alkyl or acyl group replaces a ring hydrogen; it is one of the usual electrophilic substitution reactions of the benzene ring.
Why Reason (R) does not explain Assertion (A)?
Being an electrophilic substitution does not stop the reaction: benzene and haloarenes undergo the same Friedel-Crafts reaction.
Aniline fails because the nitrogen gives its lone pair to AlCl3 and acquires a positive charge; the group then acts as a strong deactivating group for the ring. (R) states a true fact, but not this cause.
NCERT (2026-27 edition):
9.6 Chemical Reactions – “Aniline does not undergo Friedel-Crafts reaction (alkylation and acetylation) due to salt formation with aluminium chloride, the Lewis acid, which is used as a catalyst. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction.”
6.7.2 Reactions of Haloarenes – “2. Electrophilic substitution reactions
Haloarenes undergo the usual electrophilic reactions of the benzene ring such as halogenation, nitration, sulphonation and Friedel-Crafts reactions.”