Nitration of benzene template

Sulfuric acid makes NO₂⁺ from nitric acid; the ring attacks it and loses H⁺ to give nitrobenzene.

Mechanism step by step

Electrophilic aromatic substitution by the nitronium ion, NO₂⁺

1. Protonation – Sulfuric acid protonates nitric acid
2. Nitronium ion – Loss of water gives NO₂⁺
3. Attack – The π system attacks NO₂⁺: arenium ion
4. Deprotonation – HSO₄⁻ removes H⁺: aromaticity returns

Key points

• Nitrating mixture: concentrated HNO₃ and H₂SO₄; keep below about 50 °C to avoid dinitration.
• The slow step is attack on NO₂⁺, which breaks aromaticity.
• The NO₂ group deactivates the ring and directs further substitution meta.
• Reduction (Sn/HCl or H₂/Pd) turns nitrobenzene into aniline.

Drawn with 94 atoms, 13 arrows, 6 shapes – every one editable in MolDraw.

Sources

• Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012, ch. 21 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook