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Systematic IUPAC name
Abbreviations NO((2.)-)
ChemSpider 2272768 N
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PubChem 3001380
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Preferred IUPAC name
Systematic IUPAC name
Other names
3DMet B00354
ChemSpider 3874228 () N
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KEGG C01818
PubChem 6185901 (E)
4686309 ()
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

A hyponitrite refers to ionic compounds that contain the hyponitrite ion, N2O22−, ([ON=NO]2−) or to organic hyponitrites (RON=NOR), for example di-tert butyl hyponitrite.

Hyponitrite ion[edit]

There are cis and trans forms of the hyponitrite ion.[1] The trans form is generally found in hyponitrite salts such as sodium hyponitrite, Na2N2O2 and silver hyponitrite, Ag2N2O2. The trans-isomer is conventionally prepared by nitrite reduction with sodium amalgam.[2][3] Sodium hyponitrite can be prepared from sodium and nitric oxide by a method described by an earlier method modified with pyridine, from sodium amalgam and sodium nitrite,[citation needed] from alkyl nitrites and hydroxylamine[4] or by electrolysis of sodium nitrite.[5]

The cis-isomer of the sodium salt, NaN2O2, can be prepared by passing nitrous oxide, NO into a solution of sodium metal in liquid ammonia at −50 °C.[1]The cis salt is more reactive than the trans. The trans - hyponitrite ion is a salt of the related trans-hyponitrous acid H2N2O2 ( HON=NOH ), the cis acid is not known.[1]
The hyponitrite ions can act as a bidentate ligand in either bridging or chelating mode. There is a bridging cis-hyponitrite group in the red dinuclear form of nitrosyl pentammine cobalt(III) chloride, [Co(NH3)5NO]Cl2.[6]
Hyponitrite can act as a reducing agent for example reducing iodine, I2,:[6]

N2O22− + 3I2 + 3H2O = [NO3] + [NO2] + 6HI

Liquid N2O4 oxidises hyponitrites to give Na2N2O3, sodium peroxohyponitrite (containing [ON=NOO]2−).[1]

Hyponitrous acid[edit]

Main article: Hyponitrous acid

Trans-hyponitrous acid forms white crystals that are explosive when dry. It is a weak acid in aqueous solution and decomposes to N2O and water with a half life of 16 days at 25 °C at pH 1-3.[1] As this reaction is not reversible N2O should not be considered as the anhydride of H2N2O2.[1] Hyponitrous acid forms salts, the "acid hyponitrites" containing the [HON=NO] anion as well as the hyponitrites that contain the [ON=NO]2− anion.[1]

Other nitrogen oxoanions[edit]

Other nitrogen oxoanions include

Alkyl hyponitrites[edit]

Silver hyponitrite reacts with alkyl halides, RX, to form organic hyponitrites, (RON=NOR), e.g. trans t-butyl hyponitrites.[7] One use of these is as a source of alkoxyl radicals.[8]


  1. ^ a b c d e f g Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
  2. ^ Addison, C. C.; Gamlen G. A.; Thompson, R. (1952). "70. The ultra-violet absorption spectra of sodium hyponitrite and sodium α-oxyhyponitrite : the analysis of mixtures with sodium nitrite and nitrate". J. Chem. Soc.: 338. doi:10.1039/jr9520000338. 
  3. ^ Neumann, R. C., Jr. Bussey, R. J. (1970). "High pressure studies. V. Activation volumes for combination and diffusion of geminate tert-butoxy radicals". J. Am. Chem. Soc. 92 (8): 2440. doi:10.1021/ja00711a039. 
  4. ^ Scott, A. W. (1927). J. Am. Chem. Soc. 49 (4): 986–7. doi:10.1021/ja01403a502.  Missing or empty |title= (help)
  5. ^ Polydoropoulos, C. N. Chem. Ind. (London) 1963, 1686 and references therein.
  6. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419. 
  7. ^ Navamoney Arulsamy, D. Scott Bohle, Jerome A. Imonigie, Elizabeth S. Sagan (2000). "Correlation of the Product E/Z Framework Geometry and O/O vs O/N Regioselectivity in the Dialkylation of Hyponitrite". J. Am. Chem. Soc. 122 (23): 5539–5549. doi:10.1021/ja994261o. 
  8. ^ Craig A. Ogle, Steven W. Martin, Michael P. Dziobak, Marek W. Urban, G. David Mendenhall (1983). "Decomposition rates, synthesis, and spectral properties of a series of alkyl hyponitrites". J. Org. Chem. 48 (21): 3728–3733. doi:10.1021/jo00169a023.