Nitronium ion

The nitronium ion, , is not stable enough to exist in normal conditions, but it is used extensively in the nitration of other substances. The ion is created in situ by mixing sulphuric acid and nitric acid according to the equilibrium:

H₂SO₄ + HNO₃ ↔ HSO₄^- + NO₂⁺ + H₂O

The nitronium ion also exists in the solid form of the nitrogen oxide N₂O₅, which is an ionic solid formed from nitronium and nitrate ions. Its liquid and gaseous forms, however, are molecular and do not contain nitronium ions.