Aryl halides do not undergo nucleophilic substitution reactions under ordinary conditions because
(A) approach of nucleophile is retarded
(B) carbon carrying halogen atom is \(sp^3\) hybridised
(C) the substrate molecule is destabilised due to resonance
(D) of partial double bond character between carbon and halogen.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A and D only
Aryl halides are much less reactive than alkyl halides towards nucleophilic substitution, for four reasons: (i) resonance gives the C–X bond partial double bond character, so it is harder to break; (ii) the carbon carrying the halogen is sp2 hybridised, so the C–X bond is shorter and stronger; (iii) the phenyl cation that an SN1 path would need is not stabilised by resonance; (iv) the electron-rich ring repels an electron-rich nucleophile, so its approach is retarded.
(A) approach of nucleophile is retarded — Correct. The π electron cloud of the ring repels the incoming nucleophile.
(B) carbon carrying halogen atom is sp3 hybridised — Incorrect. The ring carbon is sp2 hybridised; it is the carbon of an alkyl halide that is sp3.
(C) the substrate molecule is destabilised due to resonance — Incorrect. Resonance stabilises the aryl halide; this extra stability is what makes the C–X bond hard to break.
(D) of partial double bond character between carbon and halogen — Correct. A lone pair of the halogen is delocalised into the ring, giving the C–X bond partial double bond character.
NCERT (2026-27 edition):
Reactions of Haloarenes
Reactions of Haloarenes – “… (iv) Because of the possible repulsion, it is less likely for the electron rich nucleophile to approach electron rich arenes.”