{{distinguish|nitromethane|methyl nitrate}} {{chembox | Verifiedfields = changed | verifiedrevid = 476992339 | ImageFile = Trans-methyl-nitrite-2D-dimensions.svg | ImageClass = skin-invert-image | ImageFile2 = Trans-methyl-nitrite-3D-vdW.png | ImageClass2 = bg-transparent | ImageSize= | PIN=Methyl nitrite | OtherNames= |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 11730 | InChI = 1/CH3NO2/c1-4-2-3/h1H3 | InChIKey = BLLFVUPNHCTMSV-UHFFFAOYAL | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/CH3NO2/c1-4-2-3/h1H3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = BLLFVUPNHCTMSV-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo=624-91-9 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 96TLP8RN37 | PubChem=12231 | SMILES = O=NOC }} |Section2={{Chembox Properties | C=1 | H=3 | N=1 | O=2 | Appearance=Yellow gas<ref name=crc/> | Density=0.991 g/cm<sup>3</sup><ref name=crc>Haynes, p. 3.382</ref> | MeltingPtC=-16 | MeltingPt_ref=<ref name=crc/> | BoilingPt_ref=<ref name=crc/> | BoilingPtC=-12 | Solubility= }} | Section4 = {{Chembox Thermochemistry | Thermochemistry_ref =<ref>Haynes, p. 5.20</ref> | HeatCapacity = | Entropy = | DeltaHform = −66.1 kJ/mol | DeltaGfree = | DeltaHcombust = | DeltaHfus = | DeltaHvap = | DeltaHsublim = | HHV = | LHV = }} |Section8={{Chembox Hazards | ExternalSDS = [http://msds.chem.ox.ac.uk/ME/methyl_nitrite.html External MSDS] | FlashPt= | AutoignitionPt = }} }}

'''Methyl nitrite''' is an organic compound with the chemical formula {{Chem|CH|3|ONO}}. It is a gas, and is the simplest alkyl nitrite.

== Structure ==

At room temperature, methyl nitrite exists as a mixture of ''cis'' and ''trans'' conformers. The ''cis'' conformer is 3.13 kJ mol<sup>−1</sup>, more stable than the ''trans'' form, with an energy barrier to rotation of 45.3 kJ mol<sup>−1</sup>.<ref>{{cite journal | journal = Journal of Physical Chemistry | year = 1990 | volume = 94 | issue = 10 | pages = 4029–39 | title=Infrared spectrum, ab initio calculations, barriers to internal rotation and structural parameters for methyl nitrite | doi = 10.1021/j100373a028 | last1 = Van Der Veken | first1 = B. J. | last2 = Maas | first2 = R. | last3 = Guirgis | first3 = G. A. | last4 = Stidham | first4 = H. D. | last5 = Sheehan | first5 = T. G. | last6 = Durig | first6 = James R. }}</ref> The cis and trans structure have also been determined by microwave spectroscopy (see external links).

{| class="wikitable" style="margin:1em auto; text-align:center;" |140px||180px |- |<small>''cis''-methyl nitrite</small>||<small>''trans''-methyl nitrite</small> |}

== Synthesis ==

Methyl nitrite can be prepared by the reaction of silver nitrite with iodomethane: Silver nitrite (AgNO<sub>2</sub>) exists in solution as the silver ion, Ag<sup>+</sup> and the nitrite ion, NO<sub>2</sub><sup>−</sup>. One of the lone pairs on an oxygen from nitrite ion attacks the methyl group (−CH<sub>3</sub>), releasing the iodide ion into solution.<ref name="organic">{{cite book |author1=Pavia, Donald L. |author2=Lampman, Gary M. |author3=Kriz, George S. |year=2004 |title=Organic Chemistry |volume=2 |location=Mason, Ohio |publisher=Thompson Custom Publishing |oclc=236055357 |isbn=978-0-03-014813-2}}</ref> Unlike silver nitrite, silver iodide is highly insoluble in water and thus forms a solid.<ref>{{cite book |author1=Darrell D. Ebbing |author2=Steven D. Gammon |year=2005 |title=General Chemistry |url=https://archive.org/details/generalchemistr000darr |url-access=registration |edition=8th |location=Boston |publisher=Houghton Mifflin |isbn=978-0-618-39941-3}}</ref> Note that nitrogen is a better nucleophile than oxygen and most nitrites would react via an S<sub>N</sub>2-like mechanism and the major product would be nitromethane. For example, sodium and potassium nitrite reacting with iodomethane would produce mostly nitromethane, with methyl nitrite as the minor product. However, the presence of the silver ion in solution has a stabilizing effect on the formation of carbocation intermediates, increasing the percent yield of methyl nitrite. In either case, some nitromethane and methyl nitrite are both formed.<ref name="organic"/>

:350px The figure shows the two gas-phase structures of methyl nitrite, as determined by IR and microwave spectroscopy.

Methyl nitrite free of nitromethane can be made by reacting iodomethane with nitrogen dioxide: :{{chem2 | 2 CH3I + 2 NO2 -> 2 CH3ONO + I2 }}

== Properties and uses == Methyl nitrite is a precursor and intermediate, e.g. during production of phenylpropanolamine.<ref name="toxnet"/>

Methyl nitrite is also present in aged cigarette smoke. Here it is presumably formed from nitrogen dioxide (itself formed by oxidation of nitric oxide) and methanol.<ref>{{Cite book | url=https://books.google.com/books?id=D2HvBQAAQBAJ&q=methyl+nitrite&pg=PA827 | title=The Chemical Components of Tobacco and Tobacco Smoke| isbn=9781466515529| last1=Rodgman| first1=Alan| last2=Perfetti| first2=Thomas A.| date=2016-04-19| publisher=CRC Press}}</ref>

==Environmental impact== As one product of the combustion of unleaded petrol in air, methyl nitrite has been proposed as a cause of the decline of insects, and hence that of songbirds in Europe.<ref>{{Cite journal|last=Summers-Smith|first=J. Denis|authorlink=J. Denis Summers-Smith|journal=British Birds|volume=100|date=September 2007|page=558|issn=0007-0335|title=Is unleaded petrol a factor in urban House Sparrow decline?}}</ref>

== Regulations == Under 15 U.S. Code § 2057b, methyl nitrite is banned due to it falling under the category of a volatile alkyl nitrite, which is intended to restrict harm that could result from the production and distribution of hazardous materials. Exceptions arise from 21 U.S.C. § 301, which permits the approved use of volatile alkyl nitrites under certain exemptions; however, it remains restricted in all cases intended for administration to a person<ref>{{Cite web |title=15 USC 2057b: Banning of isopropal nitrite and other nitrites |url=https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title15-section2057b&num=0&edition=prelim |access-date=2025-12-15 |website=uscode.house.gov}}</ref>. The aspects of methyl nitrite result in it being difficult to properly contain due to its gaseous form at room temperature, which results in it being highly unstable. As a result, the transportation of methyl nitrite has been banned within the United States under the Hazardous Materials Regulations (HMR). Methyl nitrite is fully restricted from all forms of transportation due to its classification within the Hazardous Material Table (HMT), which classifies it as forbidden<ref>{{Cite web |title=49 CFR 172.101 -- Purpose and use of the hazardous materials table. |url=https://www.ecfr.gov/current/title-49/part-172/section-172.101 |access-date=2025-12-15 |website=www.ecfr.gov |language=en}}</ref>.

==Safety== Methyl nitrite is a toxic asphyxiating gas, a potent cyanotic agent. Exposure may result in methemoglobinemia.<ref name="toxnet">[https://web.archive.org/web/20170320233917/https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+7197 METHYL NITRITE – National Library of Medicine HSDB Database]. Toxnet.nlm.nih.gov. Retrieved on 2019-03-10.</ref>

Methyl nitrite is an oxidizing agent and a heat-sensitive explosive; its sensitivity increases in presence of metal oxides. With inorganic bases it forms explosive salts. It forms explosive mixtures with air. It is used as a rocket propellant, a monopropellant.<ref>[https://cameochemicals.noaa.gov/chemical/3953 Methyl Nitrite]. Cameochemicals.noaa.gov. Retrieved on 2019-03-10.</ref> It explodes more violently than ethyl nitrite. Lower alkyl nitrites may decompose and burst the container even when stored under refrigeration.<ref>{{Cite book | url=https://books.google.com/books?id=4_PJCgAAQBAJ&q=methyl+nitrite&pg=PA1501 | title=Bretherick's Handbook of Reactive Chemical Hazards| isbn=9781483162508| last1=Bretherick| first1=L.| date=2016-10-27| publisher=Elsevier}}</ref>

== See also ==

* Nitromethane * Organic chemistry * Nucleophilic substitution

== References ==

{{Reflist}}

==Cited sources== *{{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = CRC Press | isbn = 978-1439855119| title-link = CRC Handbook of Chemistry and Physics }}

==External links== {{Commonscat}} *[https://webbook.nist.gov/cgi/cbook.cgi?ID=C624919 WebBook page for CH3NO2] *[http://pubs.acs.org/doi/abs/10.1021/j100474a023 Determination of cis and trans structures of methyl nitrite by microwave spectroscopy.]

{{Nitric oxide signaling}}

Category:Antianginals Category:Antidotes Category:Methyl esters Category:Alkyl nitrites Category:Explosive gases Category:Explosive chemicals