The chlorine atom of chlorobenzene withdraws electrons from the ring through its inductive effect and releases electrons into the ring through resonance. When chlorobenzene is nitrated, which of these effects controls the reactivity of the ring and which controls the orientation (position) of the incoming group, respectively?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Inductive effect; resonance effect
The two effects of chlorine act in opposite directions, and they are not equally strong.
Reactivity: the inductive effect is stronger than resonance, so chlorine causes a net withdrawal of electrons. The ring is deactivated, and nitration of chlorobenzene is slower than that of benzene.
Orientation: through resonance chlorine stabilises the intermediate carbocation, and this effect is more pronounced for attack at the ortho and para positions. So the nitro group enters ortho and para to chlorine, giving 1-chloro-2-nitrobenzene and 1-chloro-4-nitrobenzene.
Why the other options are incorrect
Option (1) Resonance effect; inductive effect — Incorrect. The roles are reversed. If resonance decided the reactivity, chlorine would activate the ring, but chlorobenzene reacts more slowly than benzene.
Option (2) Inductive effect; inductive effect — Incorrect. The inductive effect withdraws electrons from all positions and does not favour ortho and para; it cannot explain why chlorine is o,p-directing.
Option (3) Resonance effect; resonance effect — Incorrect. Resonance decides only the positions; the weaker resonance effect is outweighed by the inductive effect in deciding the rate.
NCERT (2026-27 edition):
6.7.2 Reactions of Haloarenes (Example 6.9) – “…Chlorine withdraws electrons through inductive effect and releases electrons through resonance. Through inductive effect, chlorine destabilises the intermediate carbocation formed during the electrophilic substitution. Through resonance, halogen tends to stabilise the carbocation and the effect is more pronounced at ortho- and para- positions. The inductive effect is stronger than resonance and causes net electron withdrawal and thus causes net deactivation. … Reactivity is thus controlled by the stronger inductive effect and orientation is controlled by resonance effect.”