Nitrite

{{Short description|Portmanteau name for nitrite derivatives}} {{Distinguish|nitride|nitrate|nitrogen dioxide}} {{Use dmy dates|date=February 2023}} {{Chembox | ImageFileL1 = Nitrit-Ion2.svg | ImageClassL1 = skin-invert | ImageAltL1 = A nitrogen atom is bonded to two oxygen atoms, with bond strength 1.5, in a bent geometry; the collective ion bears a single negative charge | ImageFileR1 = Nitrite-3D-vdW.png | ImageAltR1 = Space-filling model of the nitrite ion | ImageClassR1 = bg-transparent | SystematicName = dioxidonitrate(1−) | IUPACName = Nitrite | Section1 = {{Chembox Identifiers | CASNo = 14797-65-0 | CASNo_Ref = {{cascite|correct|CAS}} | UNII = J39976L608 | UNII_Ref = {{fdacite|correct|FDA}} | EINECS = 233-272-6 | PubChem = 946 | ChemSpiderID = 921 | SMILES = N(=O)[O-] | InChI = 1/HNO2/c2-1-3/h(H,2,3)/p-1 | InChIKey = IOVCWXUNBOPUCH-REWHXWOFAR | StdInChI = 1S/HNO2/c2-1-3/h(H,2,3)/p-1 | StdInChIKey = IOVCWXUNBOPUCH-UHFFFAOYSA-M | RTECS = | MeSHName = | ChEBI = 16301 }} | Section2 = {{Chembox Properties | Formula = {{chem2|NO2-}} | N=1 | O=2 | Appearance = | Solubility = | ConjugateAcid = Nitrous acid}} | Section3 = {{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}

The '''nitrite''' ion has the chemical formula {{chem2|NO2-}}. Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries.<ref name=Ullmann>{{Ullmann |first1=Wolfgang |last1=Laue |first2=Michael |last2=Thiemann |first3=Erich |last3=Scheibler |first4=Karl Wilhelm |last4=Wiegand |title=Nitrates and Nitrites |year=2006 |doi=10.1002/14356007.a17_265}}</ref> The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid.

== Production == Sodium nitrite is made industrially by passing a mixture of nitrogen oxides into aqueous sodium hydroxide or sodium carbonate solution:<ref name=p461/><ref name=Ullmann/> : {{chem2|NO + NO2 + 2 NaOH -> 2 NaNO2 + H2O}} : {{chem2|NO + NO2 + Na2CO3 -> 2 NaNO2 + CO2}}

The product is purified by recrystallization. Alkali metal nitrites are thermally stable up to and beyond their melting point ({{convert|441|C}} for {{chem2|KNO2}}). Ammonium nitrite can be made from dinitrogen trioxide, {{chem2|N2O3}}, which is formally the anhydride of nitrous acid: : {{chem2|2 NH3 + H2O + N2O3 -> 2 NH4NO2}}

== Structure == {{unreferenced section|date=November 2025}} [[Image:Nitrite-ion-canonical-structures.svg|thumb|200px|class=skin-invert-image|The two canonical structures of {{chem2|NO2-}}, which contribute to the resonance hybrid for the nitrite ion]] [[File:Trans-nitrous-acid-2D-dimensions.png|thumb|200px|class=skin-invert-image|Dimensions of ''trans''-HONO (from the microwave spectrum)]] The nitrite ion has a symmetrical structure (C{{sub|2v}}) symmetry), with both N–O bonds having equal length and a bond angle of about 115°. In valence bond theory, it is described as a resonance hybrid with equal contributions from two canonical forms that are mirror images of each other. In molecular orbital theory, there is a sigma bond between each oxygen atom and the nitrogen atom, and a delocalized pi bond made from the p orbitals on nitrogen and oxygen atoms, which is perpendicular to the plane of the molecule. The negative charge of the ion is equally distributed on the two oxygen atoms. Both nitrogen and oxygen atoms carry a lone pair of electrons. Therefore, the nitrite ion is a Lewis base.

In the gas phase, it exists predominantly as a ''trans''-planar molecule.

== Reactions == === Acid-base properties === Nitrite is the conjugate base of the weak acid nitrous acid: : {{chem2|HNO2 <-> H+}} + {{chem2|NO2-}};{{spaces|5}} p''K''{{sub|a}} ≈ 3.3 at {{convert|18|C}}{{cn|date=November 2025}}

Nitrous acid is also highly unstable, tending to disproportionate: : {{chem2|3 HNO2(aq) <-> H3O+ + 2 NO}} + {{chem2|NO3-}}

This reaction is slow at {{convert|0|C}}.<ref name=p461/> Addition of acid to a solution of a nitrite in the presence of a reducing agent, such as iron(II), is a way to make nitric oxide (NO) in the laboratory.

=== Oxidation and reduction === The formal oxidation state of the nitrogen atom in nitrite is +3. This means it can be either oxidized to oxidation states +4 and +5 or reduced to as low as −3. Standard reduction potentials for reactions directly involving nitrous acid are shown in the table below:<ref>{{Greenwood&Earnshaw2nd|page=431}}</ref> :{|class="wikitable" |- !Half-reaction||''E''{{sup|0}} (V) |- | {{chem2|NO3-}} + {{chem2|3 H+ + 2 e− <-> HNO2 + H2O}} || {{val|+0.94}} |- | {{chem2|2 HNO2 + 4 H+ + 4 e− <-> H2N2O2 + 2 H2O}} || {{val|+0.86}} |- | {{chem2|N2O4 + 2 H+ + 2 e− <-> 2 HNO2}} || {{val|+1.065}} |- | {{chem2|2 HNO2 + 4 H+ + 4 e− <-> N2O + 3 H2O}} || {{val|+1.29}} |} The data can be extended to include products in lower oxidation states. For example: : {{chem2|H2N2O2 + 2 H+ + 2 e− <-> N2 + 2 H2O}};{{spaces|5}} ''E''{{sup|0}} = {{val|+2.65|u=V}}

Oxidation reactions usually result in the formation of the nitrate ion, with nitrogen in oxidation state +5. For example, oxidation with permanganate ion can be used for quantitative analysis of nitrite (by titration): : {{chem2|5 NO2- + 2 MnO4- + 6 H+ -> 2 Mn(2+) + 3 H2O + 5 NO3-}}

The products of reduction reactions with the nitrite ion vary depending on the reducing agent used and its strength. With sulfur dioxide, the products are NO and {{chem2|N2O}}; with tin(II) ({{chem2|Sn(2+)}}) the product is hyponitrous acid ({{chem2|H2N2O2}}); reduction all the way to ammonia ({{chem2|NH3}}) occurs with hydrogen sulfide. With the hydrazinium cation ({{chem2|N2H5+}}) the product of nitrite reduction is hydrazoic acid ({{chem2|HN3}}), an unstable and explosive compound:

: {{chem2|N2H5+ + HNO2 -> HN3 + H2O + H3O+}}

which can also further react with nitrite: : {{chem2|HNO2 + HN3 -> N2O + N2 + H2O}}

This reaction is unusual in that it involves compounds with nitrogen in four different oxidation states.<ref name=p461>{{Greenwood&Earnshaw2nd|pages=461–464}}</ref>

=== Analysis of nitrite === {{See also|Nitrite test}} Nitrite is detected and analyzed by the Griess Reaction, involving the formation of a deep red-colored azo dye upon treatment of a {{chem2|NO2-}}-containing sample with sulfanilic acid and naphthyl-1-amine in the presence of acid.<ref>{{Cite journal |last=Ivanov |first=V. M. |date=2004-10-01 |title=The 125th Anniversary of the Griess Reagent |journal=Journal of Analytical Chemistry |language=en |volume=59 |issue=10 |pages=1002–1005 |doi=10.1023/B:JANC.0000043920.77446.d7 |s2cid=98768756 |issn=1608-3199}}</ref>

=== Coordination complexes === {{main|Transition metal nitrite complex}} Nitrite is an ambidentate ligand and can form a wide variety of coordination complexes by binding to metal ions in several ways. For example, the red nitrito pentaamminecobalt complex {{chem2|[Co(NH3)5(ONO)](2+)}} is metastable, isomerizing to the yellow [[Nitropentaamminecobalt(III) chloride|nitro complex {{chem2|[Co(NH3)5(NO2)](2+)}}]].<ref name=p461/>

Nitrite is processed by several enzymes, all of which utilize coordination complexes.{{cn|date=November 2025}}

=== Hazardous reactions === When heated with cyanides or thiosulfates, nitrites violently explode.<ref>{{cite tech report |title=Encyclopedia of Explosives and Related Items |volume=8, M1 Thickener through Pyruvonitrolic Acid |chapter=N – Nitrites |page=N107 |first=Seymour M. |last=Kaye |date=1 January 1978 |publisher=Army Armament Research And Development Center – Large Caliber Weapon Systems Lab |location=Dover, NJ |url=https://apps.dtic.mil/sti/pdfs/ADA057762.pdf#page=292 |id=ADA057762, PATR 2700 |lccn=61-61759}}</ref>

== Biochemistry == [[File:Nitrogen Cycle - Reactions and Enzymes.svg|thumb|upright=1.5|class=skin-invert-image|A schematic representation of the microbial nitrogen cycle.<ref>{{Cite journal|last1=Sparacino-Watkins|first1=Courtney|last2=Stolz|first2=John F.|last3=Basu|first3=Partha|date=2013-12-16|title=Nitrate and periplasmic nitrate reductases|journal=Chem. Soc. Rev.|language=en|volume=43|issue=2|pages=676–706|doi=10.1039/c3cs60249d|pmid=24141308|issn=1460-4744|pmc=4080430}}</ref><ref>{{Cite journal|last1=Simon|first1=Jörg|last2=Klotz|first2=Martin G.|title=Diversity and evolution of bioenergetic systems involved in microbial nitrogen compound transformations|journal=Biochimica et Biophysica Acta (BBA) - Bioenergetics|language=en|volume=1827|issue=2|pages=114–135|doi=10.1016/j.bbabio.2012.07.005|pmid=22842521|year=2013|doi-access=free}}</ref> ANAMMOX is anaerobic ammonium oxidation, DNRA is dissimilatory nitrate reduction to ammonium, and COMMAMOX is complete ammonium oxidation.]]

In nitrification, ammonium is converted to nitrite. Important species include ''Nitrosomonas''. Other bacterial species, such as ''Nitrobacter'', are responsible for oxidizing nitrite to nitrate.{{cn|date=November 2025}}

Nitrite can be reduced to nitric oxide or ammonia by many species of bacteria. Under hypoxic conditions, nitrite may release nitric oxide, which causes potent vasodilation. Several mechanisms for nitrite conversion to NO have been described, including enzymatic reduction by xanthine oxidoreductase, nitrite reductase, and NO synthase (NOS), as well as nonenzymatic acidic disproportionation reactions.{{cn|date=November 2025}}

== Uses == === Chemical precursor === Azo dyes and other colorants are prepared by the process called diazotization, which requires nitrite.<ref name=Ullmann/>

=== Nitrite in food preservation and biochemistry === {{Undue weight|section|reason=There are lots of questionable sources mixed in with normal ones being used to push an agenda here, and this much information on food/nutrition aspects probably doesn't belong in what is otherwise a chemistry article about nitrite in the first place. Or, more to the point, since nitrite's dangers in food are well-known at this point in time, why does this section seem like it's trying to convince me from the point of view of a partially deranged vegan?|date=November 2025}} {{see also|Nitrosamine formation during digestion}} The addition of nitrites and nitrates to processed meats such as ham, bacon, and sausages speeds up the curing of meat and also imparts an attractive colour. Nitrite reacts with the meat's myoglobin by attaching to the heme iron atom, forming reddish-brown nitrosomyoglobin and the characteristic pink "fresh" color of nitrosohemochrome or nitrosyl-heme upon cooking.<ref name=ind>{{cite journal |last1=Pappenberger |first1=Günter |last2=Hohmann |first2=Hans-Peter |title=Industrial Production of <small>L</small>-Ascorbic Acid (Vitamin C) and <small>D</small>-Isoascorbic Acid |journal=Biotechnology of Food and Feed Additives |series=Advances in Biochemical Engineering/Biotechnology |date=2013 |volume=143 |pages=143–188 |doi=10.1007/10_2013_243|pmid=24258144 |isbn=978-3-662-43760-5 }}</ref> <ref name="Wilson">{{cite news |last=Wilson |first=Bee |date=2018-03-01 |title=Yes, bacon really is killing us |url=https://www.theguardian.com/news/2018/mar/01/bacon-cancer-processed-meats-nitrates-nitrites-sausages |url-status=live |work=The Guardian |location=London |language=en-GB |issn=0261-3077 |archive-url=https://web.archive.org/web/20210210183650/https://www.theguardian.com/news/2018/mar/01/bacon-cancer-processed-meats-nitrates-nitrites-sausages |archive-date=2021-02-10 |access-date=2021-02-14 |quote=In trade journals of the 1960s, the firms who sold nitrite powders to ham-makers spoke quite openly about how the main advantage was to increase profit margins by speeding up production.}}</ref>

The academic and industrial consensus is that nitrites also reduce the growth and toxin production of ''Clostridium botulinum''.<ref>{{cite journal |vauthors=Christiansen LN, Johnston RW, Kautter DA, Howard JW, Aunan WJ |title=Effect of nitrite and nitrate on toxin production by Clostridium botulinum and on nitrosamine formation in perishable canned comminuted cured meat |journal=Applied Microbiology |volume=25 |issue=3 |pages=357–362 |date=March 1973 |pmid=4572891 |pmc=380811 |doi=10.1128/AEM.25.3.357-362.1973 }}</ref><ref>{{Cite journal |last1=Lee |first1=Soomin |last2=Lee |first2=Heeyoung |last3=Kim |first3=Sejeong |last4=Lee |first4=Jeeyeon |last5=Ha |first5=Jimyeong |last6=Choi |first6=Yukyung |last7=Oh |first7=Hyemin |last8=Choi |first8=Kyoung-Hee |last9=Yoon |first9=Yohan |date=August 2018 |title=Microbiological safety of processed meat products formulated with low nitrite concentration — A review |journal=Asian-Australasian Journal of Animal Sciences |volume=31 |issue=8 |pages=1073–1077 |doi=10.5713/ajas.17.0675 |issn=1011-2367 |pmc=6043430 |pmid=29531192}}</ref><ref>{{cite journal |last1=Sindelar |first1=Jeffrey J. |last2=Milkowski |first2=Andrew L. |title=Human safety controversies surrounding nitrate and nitrite in the diet |journal=Nitric Oxide |date=May 2012 |volume=26 |issue=4 |pages=259–266 |doi=10.1016/j.niox.2012.03.011 |pmid=22487433 }}</ref>

On the other hand, a 2018 study by the British Meat Producers Association determined that legally permitted levels of nitrite do not affect the growth of ''C. botulinum''.<ref>{{cite news |last=Doward |first=Jamie |date=2019-03-23 |title=Revealed: no need to add cancer-risk nitrites to ham |url=https://www.theguardian.com/food/2019/mar/23/nitrites-ham-bacon-cancer-risk-additives-meat-industry-confidential--report |url-status=live |work=The Observer |location=London |archive-url=https://web.archive.org/web/20210126134441/https://www.theguardian.com/food/2019/mar/23/nitrites-ham-bacon-cancer-risk-additives-meat-industry-confidential--report |archive-date=2021-01-26 |access-date=2021-02-14 |quote=The results show that there is no change in levels of inoculated ''C. botulinum'' over the curing process, which implies that the action of nitrite during curing is not toxic to ''C. botulinum'' spores at levels of 150ppm [parts per million] ingoing nitrite and below.}}</ref>

Addition of ascorbic acid, erythorbic acid, or one of their salts enhances the binding of nitrite to the iron atom in myoglobin.<ref name=ind/> These chemicals also reduce the formation of nitrosamine in the stomach, but only when the fat content of a meal is less than 10%, beyond which they instead increase the formation of nitrosamine.<ref>{{cite journal |pmid=17785370 |pmc=2095705 |year=2007 |last1=Combet |first1=E. |title=Fat transforms ascorbic acid from inhibiting to promoting acid-catalysed ''N''-nitrosation |journal=Gut |volume=56 |issue=12 |pages=1678–1684 |last2=Paterson |first2=S. |last3=Iijima |first3=K. |last4=Winter |first4=J. |last5=Mullen |first5=W |last6=Crozier |first6=A. |last7=Preston |first7=T. |last8=McColl |first8=K. E. |doi=10.1136/gut.2007.128587}}</ref><ref>{{cite journal |pmid=20026204 |year=2010 |last1=Combet |first1=E. |title=Dietary phenolic acids and ascorbic acid: Influence on acid-catalyzed nitrosative chemistry in the presence and absence of lipids |journal=Free Radical Biology and Medicine |volume=48 |issue=6 |pages=763–771 |last2=El Mesmari |first2=A. |last3=Preston |first3=T. |last4=Crozier |first4=A. |last5=McColl |first5=K. E. |doi=10.1016/j.freeradbiomed.2009.12.011}}</ref>

In the U.S., meat cannot be labeled "cured" unless it contains nitrite.<ref>{{Cite book|title=Food Safety and Toxicity |first=John |last=De Vries|publisher=CRC Press |year=1997|isbn=978-0-8493-9488-1|page=70}}</ref><ref>[https://web.archive.org/web/20090617075537/http://www.meatami.com/ht/a/GetDocumentAction/i/44170 sodium nitrite and nitrate facts] Accessed 12 Dec 2014</ref><ref name="CMSFB">{{cite book | url=https://books.google.com/books?id=5IS2n8MBpf8C&pg=PA78 | title=Compendium of the Microbiological Spoilage of Foods and Beverages | page=78| isbn=978-1-4419-0826-1 | last1=Doyle | first1=Michael P. | last2=Sperber | first2=William H. | date=23 September 2009 | publisher=Springer }}</ref> In the US, nitrite has been formally used since 1925. According to scientists working for the industry group American Meat Institute, this use of nitrite started in the Middle Ages.<ref>{{Cite journal|last1=Binkerd|first1=E. F.|last2=Kolari|first2=O. E.|date=1975-01-01|title=The history and use of nitrate and nitrite in the curing of meat|journal=Food and Cosmetics Toxicology|volume=13|issue=6|pages=655–661|doi=10.1016/0015-6264(75)90157-1|issn=0015-6264|pmid=1107192}}</ref>

In some countries,{{which?|date=November 2025}} cured-meat products are manufactured without nitrate or nitrite, and without nitrite from vegetable sources. Parma ham, produced without nitrite since 1993, was reported in 2018 to have caused no cases of botulism. This is because the muscle's interior is sterile, while its surface is exposed to oxygen.<ref name=Wilson /> Other manufacturing processes do not assure these conditions, and reduction of nitrite results in toxin production.<ref>{{cite journal |last1=Lebrun |first1=S. |last2=Van Nieuwenhuysen |first2=T. |last3=Crèvecoeur |first3=S. |last4=Vanleyssem |first4=R. |last5=Thimister |first5=J. |last6=Denayer |first6=S. |last7=Jeuge |first7=S. |last8=Daube |first8=G. |last9=Clinquart |first9=A. |last10=Fremaux |first10=B. |title=Influence of reduced levels or suppression of sodium nitrite on the outgrowth and toxinogenesis of psychrotrophic Clostridium botulinum Group II type B in cooked ham |journal=International Journal of Food Microbiology |date=December 2020 |volume=334 |article-number=108853 |doi=10.1016/j.ijfoodmicro.2020.108853 |pmid=32932195 }}</ref>

Historians and epidemiologists argue{{weasel inline|date=November 2025}} that the widespread use of nitrite in meat-curing is closely linked to the development of industrial meat-processing.<ref>{{cite book |last=Coudray |first=Guillaume |year=2017 |title=Cochonneries: Comment la charcuterie est devenue un poison |language=fr |location=Paris |publisher=La Découverte |pages=40–70 |isbn=978-2-7071-9358-2}}</ref><ref>{{Cite journal|last=Lauer|first=Klaus|date=1991-01-01|title=The history of nitrite in human nutrition: A contribution from German cookery books|url=https://www.jclinepi.com/article/0895-4356(91)90037-A/abstract|journal=Journal of Clinical Epidemiology|language=en|volume=44|issue=3|pages=261–264|doi=10.1016/0895-4356(91)90037-A|issn=0895-4356|pmid=1999685|url-access=subscription}}</ref> French investigative journalist Guillaume Coudray asserts that the meat industry chooses to cure its meats with nitrite even though it is established that this chemical gives rise to cancer-causing nitroso-compounds.{{citation needed|reason="Corporate crime reporter dot com" isn't going to be unbiased about literally any issue on the planet|date=November 2025}} Some traditional and artisanal producers avoid nitrites. As many researchers{{who?|date=November 2025}} nowadays{{when?|date=November 2025}} try to point out the hazardous generation of nitrosamines as nitrites bind to free peptides in the gastrointestinal system, the EU published a regulation that requires lowering nitrite levels in meat curing from {{val|150|to|80|u=ppm}}.<ref>{{Cite news |title=Commission Decision (EU) 2024/1225 of 30 April 2024 concerning national provisions notified by Denmark on the addition of nitrite to certain meat products |url=https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=OJ:L_202401225}}</ref>

In mice, food rich in nitrites together with unsaturated fats can prevent hypertension by forming nitro fatty acids that inhibit soluble epoxide hydrolase, which is one explanation for the apparent health effect of the Mediterranean diet.<ref>{{Cite journal | doi = 10.1073/pnas.1402965111| title = Protection from hypertension in mice by the Mediterranean diet is mediated by nitro fatty acid inhibition of soluble epoxide hydrolase| journal = Proceedings of the National Academy of Sciences| volume = 111| issue = 22| pages = 8167–8172| year = 2014| last1 = Charles | first1 = R. L.| last2 = Rudyk | first2 = O.| last3 = Prysyazhna | first3 = O.| last4 = Kamynina | first4 = A.| last5 = Yang | first5 = J.| last6 = Morisseau | first6 = C.| last7 = Hammock | first7 = B. D.| last8 = Freeman | first8 = B. A.| last9 = Eaton | first9 = P. | pmid=24843165 | pmc=4050620 | bibcode = 2014PNAS..111.8167C| doi-access = free}}</ref> Adding nitrites to meat has been shown to generate known carcinogens; the World Health Organization (WHO) advises that eating {{convert|50|g|abbr=on}} of nitrite processed meat a day would raise the risk of getting bowel cancer by 18% over a lifetime.<ref name=Wilson/>

The recommended maximum limits by the World Health Organization in drinking water are {{val|3|u=mg/L}} and {{val|50|u=mg/L}} for nitrite and nitrate ions, respectively. Ingesting too much nitrite and/or nitrate through well water is suspected to cause methemoglobinemia.<ref name="ReferenceB">{{Cite journal |doi=10.1016/j.jhazmat.2016.11.055 |pmid=27894754 |title=Composite of Cu metal nanoparticles—multiwall carbon nanotubes—reduced graphene oxide as a novel and high-performance platform of the electrochemical sensor for simultaneous determination of nitrite and nitrate |journal=Journal of Hazardous Materials |volume=324 |issue=Pt B |pages=762–772 |year=2017 |last1=Bagheri |first1=H. | last2=Hajian |first2=A. |last3=Rezaei |first3=M. |last4=Shirzadmehr |first4=A. |bibcode=2017JHzM..324..762B}}</ref><ref>{{Cite journal |display-authors=6 |vauthors=Powlson DS, Addiscott TM, Benjamin N, Cassman KG, de Kok TM, van Grinsven H, L'Hirondel JL, Avery AA, van Kessel C |year=2008 |title=When does nitrate become a risk for humans? |url=https://digitalcommons.unl.edu/agronomyfacpub/102 |archive-url=https://web.archive.org/web/20180722081620/https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1102&context=agronomyfacpub |archive-date=22 July 2018 |journal=Journal of Environmental Quality |volume=37 |issue=2 |pages=291–295 |bibcode=2008JEnvQ..37..291P |doi=10.2134/jeq2007.0177 |pmid=18268290 |s2cid=14097832 }}</ref>

95% of the nitrite ingested in modern diets comes from bacterial conversion of nitrates naturally found in vegetables.<ref>{{Cite web |title=Is celery juice a viable alternative to nitrites in cured meats? |url=https://www.mcgill.ca/oss/article/food/celery-juice-viable-alternative-nitrites-cured-meats |access-date=2022-09-14 |website=Office for Science and Society |language=en}}</ref> However, potentially cancer-causing nitroso compounds are not formed in the pH-neutral colon. They are mostly produced in the acidic stomach.<ref>{{cite journal | pmid = 7285009 | volume=41 | issue=10 | title=Absence of volatile nitrosamines in human feces |date=October 1981 | journal=Cancer Res. | pages=3992–3994 | last1 = Lee | first1 = L | last2 = Archer | first2 = MC | last3 = Bruce | first3 = WR}}</ref><ref>{{cite journal | doi = 10.1016/j.freeradbiomed.2007.03.011 | pmid = 17761300 | volume=43 | issue=7 | title=Diet-induced endogenous formation of nitroso compounds in the GI tract |date=October 2007 | journal=Free Radic. Biol. Med. | pages=1040–1047 | last1 = Kuhnle | first1 = GG | last2 = Story | first2 = GW | last3 = Reda | first3 = T |display-authors=etal }}</ref>

Since the 1980s, sorbic acid and its salts have been used to inhibit ''Clostridium botulinum'' in meat products, replacing nitrites to avoid the formation of carcinogenic nitrosamines.<ref name="Naidu">{{cite book|title=Natural food antimicrobial systems |year=2000|isbn=0-8493-2047-X|page=637|publisher=CRC Press |url=https://books.google.com/books?id=_rmdPO9BNBcC&q=%22sorbic+acid%22&pg=PA637|editor= A. S. Naidu}}</ref>

=== Antidote for cyanide poisoning === Nitrites in the form of sodium nitrite and amyl nitrite are components of many cyanide antidote kits.<ref>{{Cite journal |last1=Meillier |first1=Andrew |last2=Heller |first2=Cara |date=2015 |title=Acute Cyanide Poisoning: Hydroxocobalamin and Sodium Thiosulfate Treatments with Two Outcomes following One Exposure Event |journal=Case Reports in Medicine |volume=2015 |article-number=217951 |doi=10.1155/2015/217951 |issn=1687-9627 |pmc=4620268 |pmid=26543483|doi-access=free }}</ref> Both of these compounds bind to hemoglobin and oxidize the {{chem2|Fe(2+)}} ions to {{chem2|Fe(3+)}} ions forming methemoglobin. Methemoglobin, in turn, binds to cyanide (CN), creating cyanmethemoglobin, effectively removing cyanide from the complex IV of the electron transport chain (ETC) in mitochondria, which is the primary site of disruption caused by cyanide. Another mechanism by which nitrites help treat cyanide toxicity is the generation of nitric oxide (NO). NO displaces the CN from the cytochrome c oxidase (ETC complex IV), making it available for methemoglobin to bind.<ref>{{Cite journal |last1=Bebarta |first1=Vikhyat S. |last2=Brittain |first2=Matthew |last3=Chan |first3=Adriano |last4=Garrett |first4=Norma |last5=Yoon |first5=David |last6=Burney |first6=Tanya |last7=Mukai |first7=David |last8=Babin |first8=Michael |last9=Pilz |first9=Renate B. |last10=Mahon |first10=Sari B. |last11=Brenner |first11=Matthew |title=Sodium Nitrite and Sodium Thiosulfate Are Effective Against Acute Cyanide Poisoning when Administered by Intramuscular Injection |date=June 2017 |journal=Annals of Emergency Medicine |volume=69 |issue=6 |pages=718–725.e4 |doi=10.1016/j.annemergmed.2016.09.034 |issn=0196-0644 |pmc=5446299 |pmid=28041825}}</ref>

== Organic nitrites == thumb|right|upright=0.5|class=skin-invert-image|A nitrite ester

In organic chemistry, alkyl nitrites are esters of nitrous acid and contain the nitrosoxy functional group. Nitro compounds contain the {{chem2|C\sNO2}} group. Nitrites have the general formula RONO, where R is an aryl or alkyl group. Amyl nitrite and other alkyl nitrites have a vasodilating action and must be handled in the laboratory with caution. They are sometimes used in medicine to treat heart disease. A classic named reaction for the synthesis of alkyl nitrites is the Meyer synthesis in which alkyl halides react with metallic nitrites to a mixture of nitroalkanes and nitrites.<ref>{{cite journal |title=Über die Nitroverbindungen der Fettreihe |author=Victor Meyer |journal=Justus Liebig's Annalen der Chemie |volume=171 |issue=1 |pages=1–56 |year=1872 |url=https://zenodo.org/record/1427331 |doi=10.1002/jlac.18741710102 |author-link=Victor Meyer |language=german}}</ref><ref>{{cite journal |title=The Relationship of the Constitution of Certain Alky Halides to the Formation of Nitroparaffins and Alkyl Nitrites |first1=R.B. |last1=Reynolds |first2=H. |last2=Adkins |journal=Journal of the American Chemical Society |volume=51 |issue=1 |pages=279–287 |year=1929 |doi=10.1021/ja01376a037 |bibcode=1929JAChS..51..279R}}</ref>

== Safety == {{see also|Curing (food preservation)#Nitrates and nitrites}} Large doses of nitrites cause acute poisoning in the form of methemoglobinemia, which can lead to death.<ref>{{cite journal | vauthors = Katabami K, Hayakawa M, Gando S | title = Severe Methemoglobinemia due to Sodium Nitrite Poisoning | journal = Case Reports in Emergency Medicine | volume = 2016 | article-number = 9013816 | date = 3 August 2016 | pmid = 27563472 | pmc = 4987464 | doi = 10.1155/2016/9013816 | doi-access = free}}</ref>

== See also == * Curing (food preservation) * Alkyl nitrites

== References == {{Reflist}}

== External links == {{Commons category|Nitrites}}

{{Nitrogen compounds}} {{Nitrites}} {{Nitric oxide signaling}} {{Authority control}}

* Category:Nitrogen oxyanions Category:Curing agents Category:Garde manger Category:Nitrogen cycle Category:Preservatives