Dinitrogen trioxide

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title: "Dinitrogen trioxide" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["nitrogen-oxides", "acidic-oxides", "acid-anhydrides", "sesquioxides"] topic_path: "general/nitrogen-oxides" source: "https://en.wikipedia.org/wiki/Dinitrogen_trioxide" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

| Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 443695072 | Name = Dinitrogen trioxide | ImageFile = Dinitrogen trioxide resonance hybrid.png | ImageClass = skin-invert-image | ImageName = Dinitrogen trioxide resonance hybrid | ImageFile1 = Beautiful nitrogen trioxide2.jpg | ImageName1 = Dinitrogen trioxide is blue | IUPACName = N-Oxonitramide | OtherNames = | Section1 = {{Chembox Identifiers | CASNo_Ref = | CASNo = 10544-73-7 | ChemSpiderID_Ref = | ChemSpiderID = 55446 | ChEBI_Ref = | ChEBI = 29799 | EINECS = 234-128-5 | PubChem = 61526 | UNNumber = 2421 | UNII_Ref = | UNII = 16E0524PXI | InChI = 1/N2O3/c3-1-2(4)5 | InChIKey = LZDSILRDTDCIQT-UHFFFAOYAC | StdInChI_Ref = | StdInChI = 1S/N2O3/c3-1-2(4)5 | StdInChIKey_Ref = | StdInChIKey = LZDSILRDTDCIQT-UHFFFAOYSA-N | SMILES = [O-]N+N=O | Section2 = {{Chembox Properties | N=2|O=3 | Appearance = Deep blue liquid | Density = | MeltingPtC = −100.7 | BoilingPtC = 3.5 | BoilingPt_notes = (dissociates) | Solubility = reacts to form nitrous acid | SolubleOther = soluble in ether | MagSus = −16.0·10−6 cm3/mol | Section3 = {{Chembox Structure | MolShape = planar, Cs | Dipole = 2.122 D | Section4 = {{Chembox Thermochemistry | DeltaHf = 91.20 kJ/mol | Entropy = 314.63 J/(mol·K) | HeatCapacity = 65.3 J/(mol·K) | Section7 = {{Chembox Hazards | GHS_ref= | GHSPictograms = | GHSSignalWord = Danger | HPhrases = | PPhrases = | NFPA-H = 4 | NFPA-F = 0 | NFPA-R = 2 | NFPA-S = OX | FlashPt = Non-flammable | Section9 = {{Chembox Related | OtherCompounds =

Dinitrogen trioxide (also known as nitrous anhydride) is the inorganic compound with the formula . It is a nitrogen oxide. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21°C (−6°F): : +
Dinitrogen trioxide is only isolable at low temperatures (i.e., in the liquid and solid phases). In liquid and solid states, it has a deep blue color. At higher temperatures the equilibrium favors the constituent gases, with KD = 193 kPa (25°C).

This compound is sometimes called "nitrogen trioxide", but this name properly refers to another compound, the (uncharged) nitrate radical .

Structure and bonding

The major isomer of dinitrogen trioxide molecule contains an N–N bond. One of the numerous resonant structures of the molecule of dinitrogen trioxide is , which can be described as a nitroso group attached to a nitro group by a single bond between the two nitrogen atoms. Similar to nitronium nitrate, this molecule can also co-exist in equilibrium with an ionic gas called nitrosonium nitrite ([NO]+[NO2]–)

Typically, N–N bonds are similar in length to that in hydrazine (145 pm). Dinitrogen trioxide, however, has an unusually long N–N bond at 186 pm. Some other nitrogen oxides also possess long N–N bonds, including dinitrogen tetroxide (175 pm). The molecule is planar and exhibits Cs symmetry. The dimensions displayed on the picture below come from microwave spectroscopy of low-temperature, gaseous : ::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/e9/Dinitrogen-trioxide-2D-geometry.png" caption="The bond lengths and angles of dinitrogen trioxide."] ::

ON-NO2 is considered as the "anhydride" of the unstable nitrous acid (), and produces it when mixed with water, although an alternative structure might be anticipated for the true anhydride of nitrous acid (i.e., ). That isomer can be produced from the reaction of tetrabutylammonium nitrite and triflic anhydride in dichloromethane solution at −30°C.

References

References

  1. "Dinitrogen trioxide".
  2. "Dinitrogen trioxide".
  3. {{Greenwood&Earnshaw1st
  4. {{Greenwood&Earnshaw2nd
  5. {{Holleman&Wiberg
  6. (2009-04-01). "Nitrosonium nitrite isomer of N2O3: Quantum-chemical data". Journal of Structural Chemistry.
  7. (2022-06-17). "Nitrosyl Triflate and Nitrous Anhydride, Same Mode of Generation, but Very Different Reaction Pathways. Direct Synthesis of 1,2-Oxazetes, Nitroso or Bisoxazo Compounds from Olefins". Organic Letters.

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nitrogen-oxidesacidic-oxidesacid-anhydridessesquioxides