Hyponitrous acid
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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Diazenediol | |||
| Systematic IUPAC name
N-(Hydroxyimino)hydroxylamine | |||
| Other names
Hyponitrous acid dimer | |||
| Identifiers | |||
| 14448-38-5 | |||
| 3D model (Jmol) | Interactive image | ||
| 3DMet | B00354 | ||
| ChEBI | CHEBI:14428 | ||
| ChemSpider | 55636 | ||
| 141300 | |||
| KEGG | C01818 | ||
| PubChem | 61744 | ||
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| 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 | |||
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Hyponitrous acid is the chemical compound H2N2O2. This can be formulated as HON=NOH and is an isomer of nitramide, (H2N−NO2). It forms white crystals that are explosive when dry.[1]
Hyponitrous acid is a weak acid (pKa1 = 7.21, pKa2 = 11.54) in aqueous solution and decomposes to N2O and water with a half-life of 16 days at 25 °C at pH 1–3.[1]
- H2N2O2 → H2O + N2O
Hyponitrous acid forms two series of salts, the "acid hyponitrites" containing [HON=NO]− anion and hyponitrites containing the [ON=NO]2− anion.[1]
The hyponitrite ion [ON=NO]2− can be prepared in aqueous solution by two methods. One method uses organic nitrites to synthesize the sodium salt:[2]
- RONO + NH2OH + 2 EtONa → Na2N2O2 + ROH + 2 EtOH
Another method is by the reduction of sodium nitrite with sodium amalgam:[3]
- 2 NaNO2 + 4 Na(Hg) + 2 H2O → Na2N2O2 + 4 NaOH + 4 Hg
The insoluble silver salt can be precipitated from the solution by the addition of silver nitrate:
- Na2N2O2 + 2 AgNO3 → Ag2N2O2 + 2 NaNO3
The free acid is then prepared from silver(I) hyponitrite and anhydrous HCl in ether:
- Ag2N2O2 + 2 HCl → H2N2O2 + 2 AgCl
There are two possible structures of hyponitrous acid, trans and cis, and the solid Na2N2O2·5H2O is confirmed to be the trans form.[2] Spectroscopic data also indicate a trans configuration of the free acid. The cis form can be prepared as the sodium salt Na2N2O2 by heating Na2O with gaseous N2O.[2]
References
- 1 2 3 Wiberg, Egon; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5.
- 1 2 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.
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.