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Hyponitrous acid

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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
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
Gmelin Reference 141300
KEGG
PubChem CID
CompTox Dashboard (EPA)
InChI
  • InChI=1S/H2N2O/c3-1-2-4/h(H,1,4)(H,2,3)Key: NFMHSPWHNQRFNR-UHFFFAOYSA-N
SMILES
  • ON=NO
Properties
Chemical formula 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 , 100 kPa). Infobox references
Chemical compound

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 forms two series of salts, the hyponitrites containing the anion, and the "acid hyponitrites" containing the anion.

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:

H 2 N 2 O 2 ⟶ H 2 O + N 2 O {\displaystyle {\ce {H2N2O2 -> H2O + N2O}}}

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

The cis acid is not known, but its sodium salt can be obtained.

Preparation

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

Ag 2 N 2 O 2 + 2 HCl ⟶ H 2 N 2 O 2 + 2 AgCl {\displaystyle {\ce {Ag2N2O2 + 2 HCl -> H2N2O2 + 2 AgCl}}}

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

NH 2 OH + HNO 2 ⟶ H 2 N 2 O 2 + H 2 O {\displaystyle {\ce {NH2OH + HNO2 -> H2N2O2 + H2O}}}

Biological aspects

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

H 2 N 2 O 2 + 2 NADH + 2 H + ⟷ 2 NH 2 OH + 2 NAD + {\displaystyle {\ce {H2N2O2 + 2 NADH + 2 H+ <-> 2 NH2OH + 2 NAD+}}}

References

  1. ^ Wiberg, Egon; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5.
  2. Perrin, D. D., ed. (1982) . Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 120. ISBN 0-08-029214-3. LCCN 82-16524.
  3. ^ 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.
  4. "ENZYME - 1.7.1.5 Hyponitrite reductase".
Hydrogen compounds
Nitrogen species
Hydrides
Organic
Oxides
Halides
Oxidation states−3, −2, −1, 0, +1, +2, +3, +4, +5 (a strongly acidic oxide)
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