Chemistry:Sodium hyponitrite

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Sodium hyponitrite (trans isomer)
Identifiers
3D model (JSmol)
ChemSpider
Properties
Na2N2O2
Molar mass 105.99 g/mol
Appearance colorless crystals
Density 2.466 g/cm3
Melting point 100 °C (212 °F; 373 K)
Boiling point 335 °C (635 °F; 608 K) decomposes
soluble
Solubility insoluble in ethanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium hyponitrite is a solid ionic compound with formula Na2N2O2 or (Na+)2[ON=NO]2−.[1]

There are cis and trans forms of the hyponitrite ion N2O2−2. The trans form is more common, but the cis form can be obtained too, and it is more reactive than the trans form.[1][2]

Trans isomer

The trans isomer is colorless and soluble in water and insoluble in ethanol and ether.[3][4]

Preparation

Sodium hyponitrite (trans) is conventionally prepared by reduction of sodium nitrite with sodium amalgam.[5][6][7]

2 NaNO2 + 4 Na(Hg) + 2 H2O → Na2N2O2 + 4 NaOH + 4 Hg

Sodium hyponitrite (trans) was prepared in 1927 by A. W. Scott by reacting alkyl nitrites, hydroxylammonium chloride, and sodium ethoxide[4][8]

RONO + NH2OH + 2 EtONa → Na2N2O2 + ROH + 2 EtOH

An earlier method, published by D. Mendenhall in 1974, reacted gaseous nitric oxide (NO) with sodium metal in 1,2-dimethoxyethane, toluene, and benzophenone. The salt was then extracted with water.[9] The method was later modified to use pyridine .

Other methods included oxidation of a concentrated solution of hydroxylamine with sodium nitrite in an alkaline medium:
NH2OH (conc.) + NaNO2 + NaOH → Na2N2O2 + 2H2O;[10]
or electrolysis of sodium nitrite.[11]

Hydrates

A variety of hydrates Na2N2O2(H2O)x of the trans isomer have been reported, with x including 2, 3.5, 4, 5, 6, 7, 8, and 9;[12][3][13] but there is some dispute.[14]

The hydration water seems to be just trapped in the crystal lattice rather than coordinated to the ions.[14] The anhydrous substance can be obtained by drying the hydrates over phosphorus pentoxide and then heating them to 120 °C.[14]

Reactions

Sodium hyponitrite (trans) in solution is decomposed by carbon dioxide CO2 from air to form sodium carbonate.[15]

Liquid N2O4 oxidises sodium hyponitrite (trans) to give sodium peroxohyponitrite Na2+2[ON=NOO]2−).[16][1]

Cis isomer

The cis isomer of sodium hyponitrite is a white crystalline solid, insoluble in aprotic solvents, and (unlike the trans isomer) decomposed by water and other protic solvents.[2]

Preparation

The cis isomer of sodium hyponitrite can be prepared by passing nitric oxide (NO) through a solution of sodium metal in liquid ammonia at −50 °C.[1]

The cis isomer was also obtained in 1996 by C. Feldmann and M. Jansen by heating sodium oxide Na2O with 77 kPa of nitrous oxide N2O (laughing gas) in a sealed tube at 360 °C for 2 hours. The two reagents combined to yield the cis hyponitrite quantitatively as white microcrystals.[8][2] It  was also obtained in 2021 by Carl Hoff and co-workers by ball milling (mechano-chemistry) sodium oxide sodium oxide Na2O with 30 psi of nitrous oxide N2O for 4 hours at room temperature.[17]

Properties and reactions

The anhydrous cis salt is stable up to 325 °C, when it disproportionates to nitrogen and sodium orthonitrite:[2]

3 Na2N2O2 → 2 (NaO)3N + 2 N2

It is generally more reactive than the trans isomer.[1]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
  2. ↑ 2.0 2.1 2.2 2.3 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. 
  3. ↑ 3.0 3.1 Oza, Trambaklal Mohanlal; Thaker, Rajnikant Hariprasad (1955). "The Thermal Decomposition of Silver Hyponitrite". Journal of the American Chemical Society 77 (19): 4976–4980. doi:10.1021/ja01624a007. Bibcode: 1955JAChS..77.4976O. 
  4. ↑ 4.0 4.1 Scott, Alfred W. (1927). "Sodium Hyponitrite". Journal of the American Chemical Society 49 (4): 986–987. doi:10.1021/ja01403a502. Bibcode: 1927JAChS..49..986S. 
  5. ↑ 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". Journal of the Chemical Society: 338–345. doi:10.1039/jr9520000338. 
  6. ↑ 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. Bibcode: 1970JAChS..92.2440N. 
  7. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. 
  8. ↑ 8.0 8.1 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. 
  9. ↑ Mendenhall, G. David (1974). "Convenient synthesis of silver hyponitrite". Journal of the American Chemical Society 96 (15): 5000. doi:10.1021/ja00822a054. Bibcode: 1974JAChS..96.5000M. 
  10. ↑ Р.А. Лидин, В.А. Молочко, Л.Л. Андреева, Химические свойства неорганических веществ: учебное пособие.
  11. ↑ Polydoropoulos, C. N. Chem. Ind. (London) 1963, 1686 and references therein.
  12. ↑ Partington, James Riddick; Shah, Chandulal Chhotalal (1931). "CCLXXXII.—Investigations on hyponitrites. Part I. Sodium hyponitrite: Preparation and properties". Journal of the Chemical Society: 2071–2080. doi:10.1039/JR9310002071. 
  13. ↑ Polydoropoulos, C.N.; Voliotis, S.D. (1967). "Sodium hyponitrite hexahydrate". Journal of Inorganic and Nuclear Chemistry 29 (12): 2899–2901. doi:10.1016/0022-1902(67)80121-0. 
  14. ↑ 14.0 14.1 14.2 Stucky, Gary L.; Lambert, Jack L.; Dean Dragsdorf, R. (1969). "The hydrates of sodium hyponitrite". Journal of Inorganic and Nuclear Chemistry 31: 29–32. doi:10.1016/0022-1902(69)80050-3. 
  15. ↑ Conner, Charlotte N.; Donald, Caroline E.; Hughes, Martin N.; Sami, Christina (1989). "The molar absorptivity of sodium hyponitrite". Polyhedron 8 (21): 2621–2622. doi:10.1016/S0277-5387(00)81166-3. 
  16. ↑ Hughes, M. N.; Nicklin, H. G. (1969). "The action of dinitrogen tetroxide on sodium hyponitrite". Journal of the Chemical Society D: Chemical Communications (2): 80a. doi:10.1039/C2969000080A. 
  17. ↑ Davis, Jack V.; Guio, Oswaldo; Captain, Burjor; Hoff, Carl D. (2021). "Production of cis -Na2N2O2 and NaNO3 by Ball Milling Na2O and N2O in Alkali Metal Halide Salts". ACS Omega 6 (28): 18248–18252. doi:10.1021/acsomega.1c02119. PMID 34308055. 



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