peroxynitrite
{{Short description|Ion}}
{{Chembox
| ImageFile = Peroxynitrite-ion-2D.png
| ImageSize = 150px
| ImageCaption = Chemical structure of the peroxynitrite anion
| IUPACName = Oxido nitrite
| OtherNames =
| Section1 = {{Chembox Identifiers
| CASNo = 19059-14-4
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = UR67NH4U77
| PubChem = 104806
| KEGG = C16845
| ChEBI = 25941
| SMILES = N(=O)O[O-]
| InChI=1S/HNO3/c2-1-4-3/h3H/p-1
| InChIKey=CMFNMSMUKZHDEY-UHFFFAOYSA-M
}}
| Section2 = {{Chembox Properties
| N=1|O=3|Formula_Charge=-
| Appearance =
| Density =
| MeltingPt =
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| Solubility =
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| Section3 = {{Chembox Hazards
| MainHazards =
| FlashPt =
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File:Reactions of peroxynitrite leading to either apoptotic or necrotic cell death.jpg
Peroxynitrite (sometimes called peroxonitrite) is an ion with the formula ONOO−. It is a structural isomer of nitrate, {{chem|NO|3|−}}
Preparation
Peroxynitrite can be prepared by the reaction of superoxide with nitric oxide:{{cite journal |doi=10.1002/0471653683.ch1|title=Tetramethylammonium Salts of Superoxide and Peroxynitrite |journal=Inorganic Syntheses |year=2004 |last1=Bohle |first1=D. Scott |last2=Sagan |first2=Elisabeth S.|pages=36 }}{{cite journal | doi = 10.1152/physrev.00029.2006 | pmid = 17237348| pmc = 2248324| year = 2007| author1 = Pacher| first1 = P| title = Nitric oxide and peroxynitrite in health and disease| journal = Physiological Reviews| volume = 87| issue = 1| pages = 315–424| last2 = Beckman| first2 = J. S| last3 = Liaudet| first3 = L}}{{cite journal | pmid = 17667957| year = 2007| author1 = Szabó| first1 = C| title = Peroxynitrite: Biochemistry, pathophysiology and development of therapeutics| journal = Nature Reviews Drug Discovery| volume = 6| issue = 8| pages = 662–80| last2 = Ischiropoulos| first2 = H| last3 = Radi| first3 = R| doi = 10.1038/nrd2222}}
:{{chem2|NO + O2- -> NO(O2)-}}
It is prepared by the reaction of hydrogen peroxide with nitrite:{{cite journal | pmid = 8944624| year = 1996| author1 = Beckman| first1 = J. S| title = Nitric oxide, superoxide, and peroxynitrite: The good, the bad, and ugly| journal = American Journal of Physiology. Cell Physiology| volume = 271| issue = 5 Pt 1| pages = C1424–37| last2 = Koppenol| first2 = W. H| doi = 10.1152/ajpcell.1996.271.5.C1424}}
: H2O2 + {{chem|NO|2|−}} → ONOO− + H2O
Its presence is indicated by the absorbance at 302 nm (pH 12, ε302 = 1670 M−1 cm−1).
Reactions
Peroxynitrite is weakly basic with a pKa of ~6.8.
It is reactive toward DNA and proteins.
ONOO− reacts nucleophilically with carbon dioxide. In vivo, the concentration of carbon dioxide is about 1 mM, and its reaction with ONOO− occurs quickly. Thus, under physiological conditions, the reaction of ONOO− with carbon dioxide to form nitrosoperoxycarbonate ({{chem|ONOOCO|2|−}}) is by far the predominant pathway for ONOO−. {{chem|ONOOCO|2|−}} homolyzes to form carbonate radical and nitrogen dioxide, again as a pair of caged radicals. Approximately 66% of the time, these two radicals recombine to form carbon dioxide and nitrate. The other 33% of the time, these two radicals escape the solvent cage and become free radicals. It is these radicals (carbonate radical and nitrogen dioxide) that are believed to cause peroxynitrite-related cellular damage.
Peroxynitrous acid
{{main|Peroxynitrous acid}}
Its conjugate acid peroxynitrous acid is highly reactive, although peroxynitrite is stable in basic solutions.Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.{{cite journal | doi = 10.1590/S0100-40421998000300014 | title = The chemistry of peroxynitrite, a biological toxin| journal = Química Nova | volume = 21 | issue = 3 | pages = 326–331 | year = 1998 | last1 = Koppenol | first1 = W. H | doi-access = free }}