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Hyponitrous acid

Hyponitrous acid
Tautomer wireframe models of hyponitrous acid
Hyponitrous acid Ball and Stick (Tautomer 1).png
Hyponitrous acid Ball and Stick (Tautomer 2).png
Names
Preferred IUPAC name
Diazenediol
Systematic IUPAC name
N-(Hydroxyimino)hydroxylamine
Other names
Hyponitrous acid dimer
Identifiers
3D model (JSmol)
3DMet B00354
ChEBI
ChemSpider
141300
KEGG
PubChem CID
Properties
H2N2O2
Molar mass 62.0282 g/mol
Appearance white crystals
Hazards
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 is a chemical compound with formula H
2
N
2
O
2
or HON=NOH. It is an isomer of nitramide, H2N−NO2.

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

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
2
O
should not be considered as the anhydride of H
2
N
2
O
2
.

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

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.

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


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