Aryl Halides are less reactive towards nucleophilic substitution reac…

The correct answer is Option (3) → (A), (B), (C) and (D)

Haloarenes are much less reactive than haloalkanes towards nucleophilic substitution. Four factors together explain this:

• (A) Resonance Effect — Correct. A lone pair of the halogen is delocalised into the benzene ring, so the C–X bond gets partial double bond character and is harder to break than in a haloalkane.

• (B) Stability of phenyl cation — Correct. The factor here is the instability of the phenyl cation: if the C–X bond ionised, the phenyl cation formed would not be stabilised by resonance (its empty orbital is an sp² orbital in the plane of the ring), so the \( \mathrm{S_N1} \) route is ruled out.

• (C) Presence of \( sp^2 \) Carbon attached to halogen — Correct. An sp² carbon has more s character and is more electronegative than an sp³ carbon. It holds the bonding pair more tightly, so the C–X bond is shorter (169 pm against 177 pm in a haloalkane) and stronger.

• (D) Repulsion between benzene ring and incoming nucleophile — Correct. The electron-rich nucleophile is repelled by the electron-rich \( \pi \) cloud of the ring, so it is less likely to approach the carbon.

Note: It seems that there is a mistake in the original NTA paper. Statement (B) prints “Stability of phenyl cation”; it should read “Instability of phenyl cation”.

NCERT (2026-27 edition):
Nucleophilic Substitution – “Aryl halides are extremely less reactive towards nucleophilic substitution reactions due to the following reasons:
(i) Resonance effect : … C—Cl bond acquires a partial double bond character due to resonance. …
(ii) Difference in hybridisation of carbon atom in C—X bond: In haloalkane, the carbon atom attached to halogen is sp³ hybridised while in case of haloarene, the carbon atom attached to halogen is sp²-hybridised. …
(iii) Instability of phenyl cation: In case of haloarenes, the phenyl cation formed as a result of self-ionisation will not be stabilised by resonance and therefore, S_N1 mechanism is ruled out.
(iv) Because of the possible repulsion, it is less likely for the electron rich nucleophile to approach electron rich arenes.”