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.
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Diazenediol | |||
| Systematic IUPAC name
N-(Hydroxyimino)hydroxylamine | |||
| Other names
Hyponitrous acid dimer | |||
| Identifiers | |||
3D model (JSmol) |
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| 3DMet | |||
| ChEBI | |||
| ChemSpider | |||
| 141300 | |||
| KEGG | |||
PubChem CID |
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CompTox Dashboard (EPA) |
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| 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).
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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]
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),[2] 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.[3]
Hyponitrous acid (trans) can be prepared from silver(I) hyponitrite and anhydrous HClinether:
Spectroscopic data indicate a trans configuration for the resulting acid.[3]
It can also be synthesized from hydroxylamine and nitrous acid:
Inenzymology, a hyponitrite reductase is an enzyme that catalyzes the chemical reaction[4]
