# Methyl nitrite

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{{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](/source/organic_compound) with the [chemical formula](/source/chemical_formula) {{Chem|CH|3|ONO}}. It is a gas, and is the simplest [alkyl nitrite](/source/alkyl_nitrites).

== Structure ==

At room temperature, methyl nitrite exists as a mixture of ''cis'' and ''trans'' [conformer](/source/conformational_isomerism)s. The ''cis'' conformer is 3.13 kJ mol<sup>−1</sup>, more stable than the ''trans'' form, with an [energy barrier](/source/activation_energy) to rotation of 45.3 kJ mol<sup>−1</sup>.<ref>{{cite journal | journal = [Journal of Physical Chemistry](/source/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](/source/silver) [nitrite](/source/nitrite) with [iodomethane](/source/iodomethane): Silver nitrite (AgNO<sub>2</sub>) exists in solution as the silver [ion](/source/ion), Ag<sup>+</sup> and the nitrite ion, NO<sub>2</sub><sup>−</sup>.  One of the [lone pair](/source/lone_pair)s on an oxygen from nitrite ion [attacks](/source/nucleophilic_attack) the methyl group (−CH<sub>3</sub>), releasing the [iodide](/source/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](/source/nitrogen) is a better nucleophile than [oxygen](/source/oxygen) and most nitrites would react via an [S<sub>N</sub>2](/source/SN2)-like mechanism and the major product would be [nitromethane](/source/nitromethane).  For example, [sodium](/source/sodium_nitrite) and [potassium nitrite](/source/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](/source/carbocation) [intermediates](/source/reaction_intermediate), 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](/source/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](/source/phenylpropanolamine).<ref name="toxnet"/>

Methyl nitrite is also present in aged cigarette smoke. Here it is presumably formed from [nitrogen dioxide](/source/nitrogen_dioxide) (itself formed by oxidation of [nitric oxide](/source/nitric_oxide)) and [methanol](/source/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](/source/unleaded_petrol) in air, methyl nitrite has been proposed as a cause of the decline of [insect](/source/insect)s, and hence that of [songbird](/source/songbird)s in [Europe](/source/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](/source/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](/source/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](/source/cyanosis) agent. Exposure may result in [methemoglobinemia](/source/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](/source/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](/source/rocket_propellant), a [monopropellant](/source/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](/source/Nitromethane)
* [Organic chemistry](/source/Organic_chemistry)
* [Nucleophilic substitution](/source/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](/source/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

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Adapted from the Wikipedia article [Methyl nitrite](https://en.wikipedia.org/wiki/Methyl_nitrite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Methyl_nitrite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.