Q. 21 The compound, which upon mono-nitration using a mixture of 𝐇𝐍𝐎𝟑 and 𝐇𝟐𝐒𝐎𝟒, does NOT give
the meta-isomer as the major product, is

Question Overview

In this question, we are asked:

Which compound, on mono-nitration using a mixture of concentrated HNO₃ and H₂SO₄, does NOT give the meta-isomer as the major product?

This is a classic electrophilic aromatic substitution (EAS) problem that tests knowledge of directing effects of substituents on a benzene ring.

Key Concept: Directing Effects in Nitration

During nitration:

• Electron-withdrawing groups (EWG) → Meta-directing

• Electron-donating groups (EDG) → Ortho/Para-directing

General Rules:

Option-Wise Analysis

Option (A): Trifluoromethyl benzene (–CF₃)

• –CF₃ is a strong electron-withdrawing group

• Withdraws electrons by –I effect

• Deactivates the ring

• Directs nitration to the meta position

✅ Meta is major
❌ Not the correct answer

Option (B): Nitrobenzene (–NO₂)

• –NO₂ is one of the strongest deactivating groups

• Withdraws electrons by both –I and –R effects

• Strongly meta-directing

✅ Meta is the major product
❌ Not the correct answer

Option (C): Acetanilide (–NHCOCH₃)

• –NHCOCH₃ donates electrons by resonance (+R effect)

• Although less activating than –NH₂, it is still an ortho/para director

• Stabilizes ortho/para carbocation intermediates

🚫 Does NOT favor meta substitution
✅ Correct Answer

Option (D): Benzoic acid (–COOH)

• –COOH is a strong electron-withdrawing group

• Deactivates the benzene ring

• Meta-directing

✅ Meta is major
❌ Not the correct answer

✅ Correct Answer

✔️ Option (C): Acetanilide

This compound does NOT give the meta isomer as the major product during nitration.

Final Conclusion

Only Option (C) contains a substituent that:

• Donates electrons via resonance

• Activates the ring

• Directs substitution to ortho and para positions

All other options contain electron-withdrawing groups, which direct nitration to the meta position.