Editing Nitronium ion (section)

{{Short description|Polyatomic ion}}
{{Distinguish|Nitrosonium|text=[[Nitrosonium]], a separate nitrogen-oxygen cation}}{{Chembox
|ImageFile2 = Nitronium-3D-balls.png
| ImageClass2 = bg-transparent
|ImageFile2_Ref = {{chemboximage|correct|??}}
|ImageSize2 = 120
|ImageName2 = Ball and stick model of nitronium
|ImageFileL1 = Nitronium-2D-dimensions.png
| ImageClassL1 = skin-invert-image
|ImageFileL1_Ref = {{chemboximage|correct|??}}
|ImageNameL1 = Skeletal formula of nitronium with some dimensions added
|ImageFileR1 = Nitronium-3D-vdW.png
| ImageClassR1 = bg-transparent
|ImageFileR1_Ref = {{chemboximage|correct|??}}
|IUPACName=Nitronium ion
|ImageNameR1 = Spacefill model of nitronium
|SystematicName = Dioxidonitrogen(1+)<ref>{{Cite web |url= http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:29424|title= dioxidonitrogen(1+) (CHEBI:29424)|work= Chemical Entities of Biological Interest (ChEBI)|location= UK|publisher =European Bioinformatics Institute}}</ref>
|Section1={{Chembox Identifiers
|CASNo = 12269-46-4
|PubChem = 3609161
|ChemSpiderID = 2844644
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChEBI = 29424
|SMILES = O=[N+]=O
|StdInChI = 1S/NO2/c2-1-3/q+1
|StdInChIKey = OMBRFUXPXNIUCZ-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
|Formula = {{chem2|[NO2]+}}
|N=1|O=2
}}
|Section3={{Chembox Thermochemistry
|Entropy = 233.86 J K<sup>−1</sup> mol<sup>−1</sup>
}}
}}

The '''nitronium ion''', {{chem2|auto=1|[NO2]+}}, is a [[cation]]. It is an [[onium ion]] because its nitrogen atom has +1 charge, similar to [[ammonium]] ion {{chem2|[NH4]+}}. It is created by the removal of an electron from the [[paramagnetic]] [[nitrogen dioxide]] [[molecule]] {{chem2|NO2}}, or the [[protonation]] of [[nitric acid]] {{chem2|HNO3}} (with removal of {{chem2|H2O}}).<ref name=G&E>{{Greenwood&Earnshaw2nd}}</ref>

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 [[chemical equilibrium|equilibrium]]:

:{{chem2|H2SO4 + HNO3 → HSO4− + [NO2]+ + H2O}}