Hyponitrite

 ( Nitrogen Oxyanions ) 

In chemistry, hyponitrite may refer to the anion (ON=NO²⁻), or to any ionic compound that contains it. In organic chemistry, it may also refer to the chemical 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. Such compounds can be viewed as salts and of hyponitrous acid. An acid hyponitrite is an ionic compound with the anion (HON=NO⁻).

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Hyponitrite ion Hyponitrite exhibits cis–trans isomerism.Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier

The trans ( E) form is generally found in hyponitrite salts such as sodium hyponitrite () and silver(I) hyponitrite ().

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

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Reactions 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)₅NOCl₂.

Hyponitrite can reduce elemental iodine to hydroiodic acid:

+ 3 + 3 → + + 6 HI

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Hyponitrite esters Organic trans-hyponitrites R¹−O−N=N−O−R² can be obtained by reacting trans silver(I) hyponitrite with various . For example, reaction with t-butyl chloride yields trans di- tert-butyl hyponitrite.

Other alkyl radicals reported in the literature include Ethyl group, and benzyl. These compounds can be a source of alkoxyl radicals.

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See also Other nitrogen include

• nitrate,
• nitrite,
• peroxynitrite, (peroxynitrite), OONO⁻
• peroxynitrate,
• trioxodinitrate, (hyponitrate), ON=NO₂²⁻
• nitroxylate, O₂N−NO₂⁴⁻
• orthonitrate,

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