Arrange the following compounds in increasing order of reactivity towards Nucleophilic Substitution Reaction.
(A) Chlorobenzene
(B) 4-Nitrochlorobenzene
(C) 2,4-Dinitrochlorobenzene
(D) 2,4,6-Trinitrochloronitrobenzene
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (C), (D)
Nucleophilic substitution in aromatic compounds is facilitated by electron withdrawing groups such as $-NO_2$ at ortho and para positions. More nitro groups increase reactivity by stabilizing the intermediate carbanion.
Explanation
Option A: Chlorobenzene
Chlorobenzene is least reactive towards nucleophilic substitution because the benzene ring stabilizes the C-Cl bond via resonance. There are no electron withdrawing groups to activate the ring.
Option B: 4-Nitrochlorobenzene
The presence of one nitro group at the para position withdraws electron density through -I and -R effects. This activates the ring for nucleophilic substitution by stabilizing the intermediate.
Option C: 2,4-Dinitrochlorobenzene
Two nitro groups at ortho and para positions increase electron withdrawal significantly. This enhances stabilization of the intermediate, increasing reactivity further.
Option D: 2,4,6-Trinitrochlorobenzene
Three nitro groups provide maximum electron withdrawal and maximum stabilization of the intermediate complex, making it the most reactive towards nucleophilic substitution.