Article · Wikipedia archive · Last revised Jun 16, 2026

Dinitrogen dioxide

Dinitrogen dioxide is an inorganic compound having molecular formula N2O2. Many structural isomers are possible. The covalent bonding pattern O=N–N=O is predicted to be the most stable isomer based on ab initio calculations and is the only one that has been experimentally produced. In the solid form, the molecules have C2v symmetry: the entire structure is planar, with the two oxygen atoms cis across the N–N bond. The O–N distance is 1.15 Å, the N–N distance is 2.33 Å, and the O=N–N angle is 95°.

Last revised
Jun 16, 2026
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Dinitrogen dioxide
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Identifiers
3D model (JSmol)
ChEBI
ChemSpider
1035
UNII
  • InChI=1S/N2O2/c3-1-2-4
    Key: AZLYZRGJCVQKKK-UHFFFAOYSA-N
  • linear: N(=O)N=O
  • cyclic: O1N=NO1
  • bicyclic: O1N2N1O2
Properties
N2O2
Molar mass 60.012 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Dinitrogen dioxide is an inorganic compound having molecular formula N
2O
2. Many structural isomers are possible. The covalent bonding pattern O=N–N=O (a non-cyclic dimer of nitric oxide (NO)) is predicted to be the most stable isomer based on ab initio calculations and is the only one that has been experimentally produced.1 In the solid form, the molecules have C2v symmetry: the entire structure is planar, with the two oxygen atoms cis across the N–N bond. The O–N distance is 1.15 Å, the N–N distance is 2.33 Å, and the O=N–N angle is 95°.2

It is an intermediate in the high-pressure disproportionation of nitric oxide:34

2NO ⇌ N2O2
N2O2 + NO → N2O + NO2
References

References

  1. Nguyen, Kiet A.; Gordon, Mark S.; Montgomery, John A. Jr.; Michels, H. Harvey (October 1994). "Structures, Bonding, and Energetics of N2O2 Isomers". The Journal of Physical Chemistry. 98 (40): 10072–10078. doi:10.1021/j100091a021.
  2. Park, Jong Keun; Sun, Hosung (1999). "Theoretical Determination of Geometrical Structures of the Nitric Oxide Dimer, (NO)2". Bulletin of the Korean Chemical Society (in Korean). 20 (12): 1399–1408. ISSN 0253-2964.
  3. Agnew, Stephan F.; Swanson, B. I.; Jones, L. H.; Mills, R. L. (April 1985). "Disproportionation of Nitric Oxide at High Pressure". The Journal of Physical Chemistry. 89 (9): 1678–1682. doi:10.1021/j100255a026.
  4. Tsukahara, Hirokazu; Ishida, Takanobu; Todoroki, Yukiko; Hiraoka, Masahiro; Mayumi, Mitsufumi (January 2003). "Gas-phase Disproportionation of Nitric Oxide at Elevated Pressures". Free Radical Research. 37 (2): 171–177. doi:10.1080/1071576021000036489.