Nitronium ion

Nitronium ion
Skeletal formula of nitronium with some dimensions added	Spacefill model of nitronium
Names
	IUPAC name Nitronium ion
	Systematic IUPAC name Dioxidonitrogen(1+)
Identifiers
CAS Number	12269-46-4;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:29424;
ChemSpider	2844644 ;
PubChem CID	3609161;
CompTox Dashboard (EPA)	DTXSID60893596 ;
	InChI InChI=1S/NO2/c2-1-3/q+1 Key: OMBRFUXPXNIUCZ-UHFFFAOYSA-N;
	SMILES O=[N+]=O;
Properties
Chemical formula	[NO2]+
Molar mass	46.005 g·mol−1
Thermochemistry
Std molar; entropy (S⦵298)	233.86 J K−1 mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The nitronium ion, [N O₂]⁺, is a cation. It is an onium ion because its nitrogen atom has +1 charge, similar to ammonium ion [NH₄]⁺. It is created by the removal of an electron from the paramagnetic nitrogen dioxide molecule NO₂, or the protonation of nitric acid HNO₃ (with removal of H₂O).^[2]

It is stable enough to exist in normal conditions, but it is generally reactive and used extensively as an electrophile in the nitration of other substances. The ion is generated in situ for this purpose by mixing concentrated sulfuric acid and concentrated nitric acid according to the equilibrium:

H₂SO₄ + HNO₃ → HSO−4 + [NO₂]⁺ + H₂O

^ "dioxidonitrogen(1+) (CHEBI:29424)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[1] "dioxidonitrogen(1+) (CHEBI:29424)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.

[G&E-2] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[1]

[2]