Question

When a nitro group is attached to a benzene ring, what effect do we observe towards reactions:

[(I)] Deactivating towards electrophilic substitution
[(II)] Activating towards electrophilic substitution
[(III)] Deactivating towards nucleophilic substitution
[(IV)] Activating towards nucleophilic substitution
Find the correct statements:

• A. I, II
• B. II, III
• C. I, IV
• D. II, IV

Hint:

Strong electron-withdrawing groups like \(-\mathrm{NO_2}\) {deactivate benzene towards electrophiles} but {activate it towards nucleophiles}.

Answer 1

The Correct Option is C

Concept:
The nitro group (\(-\mathrm{NO_2}\)) is a strongly electron-withdrawing group
due to both:

\(-I\) (inductive) effect
\(-M\) (mesomeric/resonance) effect
Its effect on different substitution reactions depends on how electron density in the benzene ring is altered. Statement-wise Analysis:
(I) Deactivating towards electrophilic substitution


Electrophilic substitution requires high electron density in the benzene ring.
Nitro group withdraws electron density, making the ring less reactive.
Hence, benzene becomes deactivated
towards electrophilic substitution.
\(\Rightarrow\) True
(II) Activating towards electrophilic substitution


This is opposite to the actual effect of nitro group.
\(\Rightarrow\) False
(III) Deactivating towards nucleophilic substitution


Nucleophilic substitution is favored by electron-deficient rings.
Nitro group increases electron deficiency of the ring.
\(\Rightarrow\) False
(IV) Activating towards nucleophilic substitution


Nitro group stabilizes the negatively charged intermediate (Meisenheimer complex).
Hence, it activates
the ring towards nucleophilic substitution.
\(\Rightarrow\) True

Final Conclusion:
Correct statements are \(\boxed{I \text{ and } IV}\).