In chemistry, hyponitrite may refer to the anion N
2
O2−
2
([ON=NO]2−), or to any ionic compound that contains it. In organic chemistry, it may also refer to the group −O−N=N−O−, or any organic compound with the generic formula R1−O−N=N−O−R2, where R1 and R2 are organic groups.[1] Such compounds can be viewed as salts and esters of hyponitrous acid. An acid hyponitrite is an ionic compound with the anion HN
2
O
2
([HON=NO]).

Hyponitrite
trans (E) hyponitrite
cis (Z) hyponitrite
Names
Preferred IUPAC name
Hyponitrite
Systematic IUPAC name
Diazenebis(olate)
Other names
Hyponitrite(2–)
Identifiers
3D model (JSmol)
3DMet
ChEBI
ChemSpider
130273
  • InChI=1S/H2N2O2/c3-1-2-4/h(H,1,4)(H,2,3)/p-2
    Key: NFMHSPWHNQRFNR-UHFFFAOYSA-L
  • (E): [O-]/N=N/[O-]
  • (Z): [O-]\N=N/[O-]
Properties
N
2
O2−
2
Molar mass 60.012 g·mol−1
Conjugate acid Hyponitrous acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Hyponitrite ion

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Hyponitrite exhibits cis–trans isomerism.[2]

The trans (E) form is generally found in hyponitrite salts such as sodium hyponitrite (Na
2
N
2
O
2
) and silver(I) hyponitrite (Ag
2
N
2
O
2
).

The cis (Z) form of sodium hyponitrite can be obtained too, but it is more reactive than the trans form.[2] The cis hyponitrite anion is nearly planar and almost symmetric, with lengths of about 140 pm for N−O bond and 120 pm for the N−N bond, and O−N−N angles of about 119°.[3]

Reactions

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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.[4]

Hyponitrite can reduce elemental iodine to hydroiodic acid:[4]

N
2
O2−
2
+ 3 I
2
+ 3 H
2
O
NO
3
+ NO
2
+ 6 HI

Hyponitrite esters

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Organic trans-hyponitrites R1−O−N=N−O−R2 can be obtained by reacting trans silver(I) hyponitrite Ag
2
N
2
O
2
with various alkyl halides. For example, reaction with tert-butyl chloride yields trans di-tert-butyl hyponitrite.[5][6][7][8]

Other alkyl radicals reported in the literature include ethyl,[9] and benzyl.[10][11][12] These compounds can be a source of alkoxyl radicals.[13]

See also

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Other nitrogen oxyanions include

References

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  1. ^ Hughes, M. N. (1968). "Hyponitrites". Quarterly Reviews, Chemical Society. 22: 1. doi:10.1039/QR9682200001.
  2. ^ a b Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
  3. ^ Feldmann, Claus; Jansen, Martin (1996). "Cis-Sodium Hyponitrite—A New Preparative Route and a Crystal Structure Analysis". Angewandte Chemie International Edition in English. 35 (15): 1728–1730. doi:10.1002/anie.199617281.
  4. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  5. ^ 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.
  6. ^ Kiefer, Hansruedi; Traylor, T.G. (1966). "Di-t-butyl hyponitrite. A convenient source of t-butoxy radicals". Tetrahedron Letters. 7 (49): 6163–6168. doi:10.1016/s0040-4039(00)70159-6. ISSN 0040-4039.
  7. ^ Huang, R. L.; Lee, Tong-Wai; Ong, S. H. (1969). "Reactions of the α-methoxybenzyl radical in carbon tetrachloride and in other solvents. Carbon tetrachloride as a chlorinating agent". J. Chem. Soc. C (1): 40–44. doi:10.1039/j39690000040. ISSN 0022-4952.
  8. ^ Neuman, Robert C.; Bussey, Robert J. (1970). "High pressure studies. V. Activation volumes for combination and diffusion of geminate tert-butoxy radicals". Journal of the American Chemical Society. 92 (8): 2440–2445. doi:10.1021/ja00711a039. ISSN 0002-7863.
  9. ^ Partington, James R.; Shah, Chandulal C. (1932). "384. Hyponitrites. Part II : metallic salts. Part III : esters". Journal of the Chemical Society: 2589. doi:10.1039/jr9320002589. ISSN 0368-1769.
  10. ^ Ho, S. K.; de Sousa, J. B. (1961). "347. Alkoxy-radicals. Part I. The kinetics of thermal decomposition of dibenzyl hyponitrite in solution". Journal of the Chemical Society: 1788. doi:10.1039/jr9610001788. ISSN 0368-1769.
  11. ^ de SOUSA, J. B.; HO, S. K. (1960). "Disproportionation and Dimerization of the Benzyloxyl Free Radical in Solution". Nature. 186 (4727): 776–778. Bibcode:1960Natur.186..776D. doi:10.1038/186776a0. ISSN 0028-0836. S2CID 4248607.
  12. ^ Ray, N. H. (1960). "794. The rates of decomposition of free-radical polymerisation-catalysts: measurements of short half-lives by a thermal method". Journal of the Chemical Society: 4023. doi:10.1039/jr9600004023. ISSN 0368-1769.
  13. ^ 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.