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:

(C) < (A) < (B) < (D)

The correct answer is Option (4) → (C) < (A) < (B) < (D)

The question asks about the reactivity order of different chlorobenzenes towards nucleophilic substitution reactions.

Nucleophilic Aromatic Substitution:

Nucleophilic substitution in aromatic compounds is generally facilitated by:

• Electron-withdrawing groups (EWGs) such as –NO₂, especially at ortho and para positions to the leaving group (–Cl here).

• These groups stabilize the negative charge developed in the Meisenheimer complex (intermediate), enhancing the reactivity.

Compounds:

• (C) Chlorobenzene – No activating group → least reactive.

• (A) 4-Nitro-1-chlorobenzene – One NO₂ at para position → more reactive than plain chlorobenzene.

• (B) 2,4-Dinitro-1-chlorobenzene – Two NO₂ groups (both ortho and para) → strongly activates → higher reactivity.

• (D) 2,4,6-Trinitro-1-chlorobenzene – Three NO₂ groups at ortho and para positions → highest reactivity.

So the correct reactivity order is:

(C) < (A) < (B) < (D)