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3D model (JSmol)
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PubChem CID
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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).
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Sodium hyponitrite is a solid ionic compound with formula Na
2N
2O
2 or (Na+
)2[ON=NO]2−.[1]
There are cis and trans forms of the hyponitrite ion N
2O2−
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]
The trans isomer is colorless and soluble in water and insoluble in ethanol and ether.[3][4]
Sodium hyponitrite (trans) is conventionally prepared by reduction of sodium nitrite with sodium amalgam.[5][6][7]
Sodium hyponitrite (trans) was prepared in 1927 by A. W. Scott by reacting alkyl nitrites, hydroxylammonium chloride, and sodium ethoxide[4][8]
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[citation needed].
Other methods included oxidation of a concentrated solution of hydroxylamine with sodium nitrite in an alkaline medium[citation needed]; or electrolysis of sodium nitrite.[10]
A variety of hydrates Na
2N
2O
2(H
2O)x of the trans isomer have been reported, with x including 2, 3.5, 4, 5, 6, 7, 8, and 9;[11][3][12] but there is some dispute.[13]
The hydration water seems to be just trapped in the crystal lattice rather than coordinated to the ions.[13] The anhydrous substance can be obtained by drying the hydrates over phosphorus pentoxide and then heating them to 120 °C.[13]
Sodium hyponitrite (trans) in solution is decomposed by carbon dioxide CO
2 from air to form sodium carbonate.[14]
Liquid N2O4 oxidises sodium hyponitrite (trans) to give sodium peroxohyponitrite Na2+
2[ON=NOO]2−).[15][1]
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]
The cis isomer of 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 Na
2O with 77 kPa of nitrous oxide N
2O (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]
The anhydrous cis salt is stable up to 325 °C, when it disproportionates to nitrogen and sodium orthonitrite:[2]
It is generally more reactive than the trans isomer.[1]