Reactivity order of following towards nucleophilic substitution reactions will be :
(A) 4-Nitro-1-chlorobenzene
(B) 2,4-Dinitro-1-chlorobenzene
(C) Chlorobenzene
(D) 2,4,6-Trinitro-1-chlorobenzene
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (C) < (A) < (B) < (D)
Haloarenes are very unreactive towards nucleophiles, because the C–X bond has partial double bond character from resonance. An electron withdrawing –NO2 group at the ortho or para position makes the reaction easier: it pulls electron density from the ring and stabilises the negatively charged intermediate (the carbanion formed when the nucleophile adds), by spreading its charge onto the oxygen atoms of the nitro group. The more nitro groups at ortho and para positions, the faster the reaction. For example, with hydroxide ion:
(C) Chlorobenzene: no nitro group; it needs 623 K and high pressure with NaOH: first.
(A) 4-Nitro-1-chlorobenzene: one para nitro group; it reacts at 443 K: second.
(B) 2,4-Dinitro-1-chlorobenzene: two nitro groups (ortho and para); it reacts at 368 K: third.
(D) 2,4,6-Trinitro-1-chlorobenzene: three nitro groups; it reacts even with warm water: last.
Shortcut: The reactivity rises with the number of nitro groups (0, 1, 2, 3); only Option (4) follows it.
NCERT (2026-27 edition):
Reactions of Haloarenes – …
