Hyponitrous acid

Hyponitrous acid is a chemical compound with formula H
2N
2O
2 or HON=NOH. It is an isomer of nitramide, H2N−NO2; and a formal dimer of azanone, HNO.

Hyponitrous acid
Tautomer wireframe models of hyponitrous acid
Names
Preferred IUPAC name
Diazenediol
Systematic IUPAC name
N-(Hydroxyimino)hydroxylamine
Other names
Hyponitrous acid dimer
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChemSpider
141300
KEGG
  • InChI=1S/H2N2O/c3-1-2-4/h(H,1,4)(H,2,3)
    Key: NFMHSPWHNQRFNR-UHFFFAOYSA-N
  • ON=NO
Properties
H2N2O2
Molar mass 62.0282 g/mol
Appearance white crystals
Conjugate base Hyponitrite
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 explosive when dry
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Hyponitrous acid forms two series of salts, the hyponitrites containing the [ON=NO]2− anion, and the "acid hyponitrites" containing the [HON=NO]− anion.[1]

Structure and properties

There are two possible structures of hyponitrous acid, trans and cis. trans-Hyponitrous acid forms white crystals that are explosive when dry. In aqueous solution, it is a weak acid (pKa1 = 7.21, pKa2 = 11.54), and decomposes to nitrous oxide and water with a half life of 16 days at 25 °C at pH 1–3:

Since this reaction is not reversible, N
2O should not be considered as the anhydride of H
2N
2O
2.[1]

The cis acid is not known,[1] but its sodium salt can be obtained.[2]

Preparation

Hyponitrous acid (trans) can be prepared from silver(I) hyponitrite and anhydrous HCl in ether:

Spectroscopic data indicate a trans configuration for the resulting acid.[2]
It can also be synthesized from hydroxylamine and nitrous acid:

Biological aspects

In enzymology, a hyponitrite reductase is an enzyme that catalyzes the chemical reaction[3]

References
  1. Wiberg, Egon; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5.
  2. Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry (3rd ed.). Pearson. p. 468. ISBN 978-0-13-175553-6.
  3. "ENZYME - 1.7.1.5 Hyponitrite reductase".
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