View source for Chemistry:Angeli's salt

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|Section1={{Chembox Identifiers
| CASNo = 13826-64-7
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = S8LUE47R4Z
| PubChem = 10129945
| StdInChI=1S/N2O3.2Na/c3-1-2(4)5;;/q;2*+1
| StdInChIKey = XDPWLJKQGUTUKZ-UHFFFAOYSA-N
| SMILES = N(=O)[N+](=O)[O-].[Na+].[Na+] }}
|Section2={{Chembox Properties
| N=2|O=3|Na=2 
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| Appearance = white solid
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|Section3={{Chembox Hazards
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'''Angeli's salt''', '''sodium trioxodinitrate''', is the [[Chemistry:Inorganic compound|inorganic compound]] with the formula Na<sub>2</sub>[N<sub>2</sub>O<sub>3</sub>]. It contains nitrogen in an unusual reduced state. It is a colorless, water-soluble solid, hence a salt. In research, this salt is used as a source of the metastable [[Chemistry:Nitroxyl|nitroxyl]] (HNO), which is a signalling molecule in nature.<ref>{{cite journal|last=Nakagawa|first=H.|title=Controlled release of HNO from chemical donors for biological applications|journal=J. Inorg. Biochem.|year=2013|volume=118|pages=187–190|doi=10.1016/j.jinorgbio.2012.10.004|pmid=23140899}}</ref> It is also known by the name '''sodium trioxodinitrate(II) monohydrate'''.

== Preparation and properties ==
As first reported by Angelo Angeli in 1896, the salt is prepared by combining hydroxylamine and an organic nitrate, as a source of nitronium ({{chem|NO|2|+}}):<ref>{{cite journal|first=A.|last=Angeli|journal=Gazz. Chim. Ital.|title=Sopra la nitroidrossilammina|trans-title=On nitrohydroxylamine|language=Italian|volume=26|pages=17–28|year=1896}}</ref><ref>{{cite book|chapter=Synthesis, chemistry, and Applications of Nitroxyl Ion Releasers Sodium Trioxodinitrate or Angeli's Salt and Piloty's Acid|last1=Hughes|first1=Martin N.|last2=Cammack|first2=Richard|series=Methods in Enzymology |title=Nitric Oxide, Part C: Biological and Antioxidant Activities |year=1999|volume=301|pages=279–287|doi=10.1016/S0076-6879(99)01092-7|pmid=9919577|isbn=9780121822026 }}</ref>
:NH<sub>2</sub>OH  +  RONO<sub>2</sub>  +  2&nbsp;NaOR′  →   ROH  + 2&nbsp;R′OH  +  Na<sub>2</sub>N<sub>2</sub>O<sub>3</sub>

The structure of the hydrate has been confirmed by [[Physics:X-ray crystallography|X-ray crystallography]]. The anion is planar. Starting from the ONN end, the bond distances are 1.35&nbsp;Å (N−O), 1.26&nbsp;Å (N−N), 1.31&nbsp;Å (N−O), and 1.32&nbsp;Å (N−-O). The negative charge is on the oxygen atoms at opposite ends of the molecule. The angles are 112.9° (O<sub>single</sub>−N−N), 118.4° (N−N−O<sub>''trans''</sub>), and 122.5° (N−N−O<sub>''cis''</sub>). This means that the nitrogen–nitrogen bond is a [[Chemistry:Double bond|double bond]], and that the ''cis'' oxygen is slightly repelled by the single oxygen.<ref>{{cite journal|last1=Hope|first1=Hakon|last2=Sequeira|first2=Michael R.|title=Angeli's salt. Crystal structure of sodium trioxodinitrate(II) monohydrate, Na<sub>2</sub>N<sub>2</sub>O<sub>3</sub>·H<sub>2</sub>O|journal=Inorganic Chemistry|date=February 1973|volume=12|issue=2|pages=286–288|doi=10.1021/ic50120a008}}</ref>

Reaction of Angeli's salt with secondary amines in the presence of a proton source results in extrusion of N<sub>2</sub> via [[Chemistry:Isodiazene|isodiazene]]s as proposed intermediates.<ref>{{cite book|title=Advanced Organic Chemistry. Part B: Reactions and Synthesis|last1=Carey|first1=Francis A.|date=2007|publisher=Springer|last2=Sundberg|first2=Richard J.|isbn=9781601195494|edition= 5th|location=New York, NY|oclc=223941000}}</ref>

==References==
{{reflist}}

[[Category:Nitrites]]
[[Category:Sodium compounds]]

{{Sourceattribution|Angeli's salt}}