Compared with the C–Cl bond in methyl chloride, the C–Cl bond in chlorobenzene is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Shorter and stronger
In chlorobenzene the chlorine is bonded to an sp2 hybridised ring carbon; in methyl chloride it is bonded to an sp3 carbon.
Hybridisation: the sp2 carbon has more s-character, is more electronegative and holds the C–Cl bonding pair more tightly.
Resonance: the lone pairs on chlorine are in conjugation with the π-electrons of the ring, so the C–Cl bond gets partial double bond character.
Result: the C–Cl bond length is 169 pm in chlorobenzene against 177 pm in a haloalkane, and the shorter bond is harder to break, so it is stronger.
Why the other options are incorrect
Option (1) Shorter and weaker — Incorrect. The bond is shorter, but a shorter bond is more difficult to break, so it is stronger, not weaker.
Option (3) Longer and weaker — Incorrect. This describes the C–Cl bond of methyl chloride compared with chlorobenzene, the reverse of what is asked.
Option (4) Longer and stronger — Incorrect. The bond in chlorobenzene is shorter (169 pm against 177 pm), not longer.
NCERT (2026-27 edition):
6.7.2 Reactions of Haloarenes – “The sp2 hybridised carbon with a greater s-character is more electronegative and can hold the electron pair of C—X bond more tightly than sp3-hybridised carbon in haloalkane with less s-chararcter. Thus, C—Cl bond length in haloalkane is 177pm while in haloarene is 169 pm. Since it is difficult to break a shorter bond than a longer bond, therefore, haloarenes are less reactive than haloalkanes towards nucleophilic substitution reaction.”