Bondline / Reactions

Nitration of benzene

Electrophilic aromatic substitution: the ring attacks NO₂⁺ to give a cation (Wheland intermediate), then loses H⁺ to restore aromaticity.

Aromatic substitution · 2 steps

Conditions

Concentrated HNO₃ + H₂SO₄ (which makes NO₂⁺), below 55 °C.

Mechanism in 2 steps

Red curly arrows show where each pair of electrons moves.

HON+OHN+OO−H2O++
Step 1A π bond of the ring attacks the nitronium ion. Aromaticity is lost (slow step).
HN+OO−H2ON+O−OH3O+H₂O++
Step 2A base removes the proton from the sp³ carbon and the ring becomes aromatic again.

About aromatic substitution reactions

Benzene keeps its stable aromatic ring by substituting rather than adding. An electrophile attacks, then a proton is lost to restore aromaticity.

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