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Electrophilic substitution — nitration of benzene
Year 2
AQA 3.3.10
Carbonyl & aromatic chemistry · conc HNO₃ + conc H₂SO₄ · ≈50 °C (warm)
Reagents: conc HNO₃ + conc H₂SO₄ · Conditions: ≈50 °C (warm)
Step 1 of 2
- 1.Two electrons from the delocalised π ring attack the electron-deficient nitrogen of NO₂⁺, forming a new C–N bond.
HNO3+H2SO4+H2SO4→NO2++HSO4−+HSO4−+H3O+
Sulfuric acid is the stronger acid: it protonates nitric acid, which then loses water to give NO₂⁺. AQA accepts HNO₃ + 2H₂SO₄ → NO₂⁺ + 2HSO₄⁻ + H₃O⁺ or the one-H₂SO₄ version.
The ring bonds to N, breaking aromaticity: the positively charged horseshoe (Wheland) intermediate.
Step 2 of 2
- 1.The C–H bonding pair moves back into the ring, restoring the delocalised aromatic system and releasing H⁺.
Aromaticity is restored and H⁺ is lost: nitrobenzene forms.
Product: nitrobenzene
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