Nitromethane: Difference between revisions

{{distinguish|nitrous oxide|methyl nitrate|methyl nitrite}}

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 408770718

| Name = Nitromethane

| ImageFileL1 = Valence structural formula of nitromethane.svg

| ImageNameL1 = Structural formula of nitromethane

| ImageFileR1 = Nitromethane-3D-vdW.png

| = Nitromethane

| PIN = Nitromethane<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 662 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4| chapter = Front Matter | doi-broken-date = 2024-04-14 }}</ref>

| SystematicName =

| OtherNames = Nitrocarbol

| IUPACName = Nitromethane

| Section1 = {{Chembox Identifiers

| SMILES = C[N+](=O)[O-]

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEBI_Ref = {{ebicite|changed|EBI}}

| ChEBI = 77701

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = RU5WG8C3F4

| RTECS = PA9800000

| KEGG_Ref = {{keggcite|changed|kegg}}

| KEGG = C19275

| Section2 = {{Chembox Properties

| Formula = CH₃NO₂

| MolarMass = 61.04 g/mol

| Appearance = colorless liquid

| Odor = Light, fruity<ref name=PGCH/>

| Density = 1.1371 g/cm³ (20 °C)<ref name=crc>Haynes, p. 3.414</ref>

| =

| SolubleOther = miscible in [[diethyl ether]], [[acetone]], [[ethanol]], [[methanol]]<ref name=crc/>

| = .

| MeltingPt_ref=<ref name=crc/>

| BoilingPtC = 101.2

| BoilingPt_ref=<ref name=crc/>

| pKa = {{Unbulleted list

| 10.21 (H₂O)<ref>Haynes, p. 5.94</ref>

| 17.2 (DMSO) <ref name=uwisconsin>{{cite web|last1=Reich|first1=Hans|title=Bordwell pKa table: "Nitroalkanes"|url=http://www.chem.wisc.edu/areas/reich/pkatable/|website=University of Wisconsin Chemistry Department|access-date=27 January 2022}}</ref>

| RefractIndex = 1.3817 (20 °C)<ref name=crc/>

| Viscosity = 0.63 [[Poise (unit)|cP]] at 25 °C<ref name="Haynes, p. 6.231">Haynes, p. 6.231</ref>

| ThermalConductivity = 0.204 W/(m·K) at 25 °C<ref name="Haynes, p. 6.231">Haynes, p. 6.231</ref>

| VaporPressure = 28 mmHg (20 °C)<ref name=PGCH/>

| MagSus = -21.0·10⁻⁶ cm³/mol<ref>Haynes, p. 3.576</ref>

| Dipole = 3.46<ref name=crc2>Haynes, p. 15.19</ref>

| CriticalTP =588 K, 6.0 MPa<ref>Haynes, p. 6.69</ref>

| = {{Chembox

| ShockSens = Low

| FrictionSens = Low

| DetonationV = 6400 m/s

}}

| Section4 = {{Chembox Thermochemistry

| Thermochemistry_ref =<ref>Haynes, p. 5.20</ref>

| HeatCapacity = 106.6 J/(mol·K)

| Entropy = 171.8 J/(mol·K)

| DeltaHform = -112.6 kJ/mol

| DeltaGfree = -14.4 kJ/mol

| DeltaHcombust =

| DeltaHfus =

| DeltaHvap =

| DeltaHsublim =

| HHV =

| LHV =

}}

| Section7 = {{Chembox Hazards

| ExternalSDS =

| MainHazards = Flammable, health hazard

| FlashPtC = 35<ref name=crc2/>

| GHSPictograms = {{GHS01}} {{GHS02}} {{GHS06}} {{GHS08}}

| GHSSignalWord = '''DANGER'''

| HPhrases = {{H-phrases|203|226|301|331|351}}

| PPhrases = {{P-phrases|210|261|280|304+340|312|370+378|403+233}}

| NFPA-H = 2

| NFPA-F = 3

| NFPA-R = 3

| IDLH = 750 ppm<ref name=PGCH>{{PGCH|0457}}</ref>

| LD50 = 940 mg/kg (oral, rat)<br/>950 mg/kg (oral, mouse)<ref name=IDLH>{{IDLH|75525|Nitromethane}}</ref>

| REL = none<ref name=PGCH/>

| PEL = TWA 100 ppm (250 mg/m³)<ref name=PGCH/>

| ExploLimits = 7–22%<ref name=crc2/>

| AutoignitionPtC =418<ref name=crc2/>

| TLV = 20 ppm<ref name=crc2/>

| LCLo = 7087 ppm (mouse, 2 h)<br/>1000 ppm (monkey)<br/>2500 ppm (rabbit, 12 h)<br/>5000 ppm (rabbit, 6 h)<ref name=IDLH/>

| LDLo = 750 mg/kg (rabbit, oral)<br/>125 mg/kg (dog, oral)<ref name=IDLH/>

}}

| Section8 = {{Chembox Related

| OtherFunction_label = [[nitro compounds]]

| OtherFunction = [[nitroethane]]

| OtherCompounds = [[methyl nitrite]]<br />[[methyl nitrate]]

'''Nitromethane''', sometimes shortened to simply "nitro", is an [[organic compound]] with the chemical formula {{chem|CH|3|NO|2}}. It is the simplest organic [[nitro compound]]. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent. As an intermediate in [[organic synthesis]], it is used widely in the manufacture of pesticides, explosives, fibers, and coatings.<ref name=Markofsky/> Nitromethane is used as a fuel additive in various [[motorsports]] and hobbies, e.g. [[Top Fuel]] [[drag racing]] and miniature [[Glow plug (model engine)|internal combustion engines]] in [[Radio-controlled aircraft|radio control]], [[control line]] and [[free flight (model aircraft)|free flight]] model aircraft.

Nitromethane is produced industrially by [[propane]] [[nitric acid]] F. This [[exothermic]] reaction produces the four industrially significant nitroalkanes: nitromethane, [[nitroethane]], 1-nitropropane, and 2-nitropropane. The reaction involves free radicals, including the alkoxyl radicals of the type CH₃CH₂CH₂O, which arise via homolysis of the corresponding nitrite [[ester]]. These alkoxy radicals are susceptible to fragmentation reactions, which explains the formation of a mixture of products.<ref name=Markofsky> B. Compounds, Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH |10.1002/14356007.a17_401}}</ref>

===Laboratory methods===

It can be prepared in other methods that are of instructional value. The reaction of [[chloroacetic acid|sodium chloroacetate]] with [[sodium nitrite]] in [[aqueous]] solution produces this compound:<ref>{{OrgSynth | author = Whitmore, F. C. | author2 = Whitmore, M. G. | title = Nitromethane | collvol = 1 | collvolpages = 401 | year = 1941 | prep = cv1p0401 }}</ref>

The use of nitromethane is as a , . It [[]], .<ref name=Markofsky/>

======

The major application is as a stabilizer in chlorinated solvents. As an organic solvent, nitromethane has an unusual combination of properties: highly polar (ε_r = 36 at 20&nbsp;°C and μ = 3.5 Debye) but aprotic and weakly basic. This combination makes it useful for dissolving positively charged, strongly electrophilic species. It is a solvent for acrylate [[monomer]]s, such as [[cyanoacrylate]]s (more commonly known as "super-glues").<ref name=Markofsky/>

===Fuel===

Although a minor application in terms of volume,<ref name=Markofsky/> nitromethane also is used as a fuel or fuel additive for sports and hobby. For some application, it is mixed with methanol in racing cars, boats, and model engines.

Nitromethane is used as a fuel in motor racing, particularly [[drag racing]], as well as for [[radio-controlled]] model power boats, [[cars]], [[airplane|plane]]s and [[helicopters]]. In this context, nitromethane is commonly referred to as "nitro fuel" or simply "nitro", and is the principal ingredient for fuel used in the "[[Top Fuel]]" category of drag racing.<ref>{{Cite web |last=Carley |first=Larry |date=2013-01-06 |title=HPBG: The Power of Racing Fuels |url=https://www.enginebuildermag.com/2013/01/hpbg-the-power-of-racing-fuels/ |access-date=2024-05-31 |website=Engine Builder Magazine |language=en-US}}</ref>

The [[oxygen]] content of nitromethane enables it to burn with much less atmospheric oxygen than conventional fuels.<ref>{{Cite web |date=2024-03-05 |title=What is Nitro Methane Fuel: Understanding High-Performance Racing's Power Source - Ran When Parked - Car, Vehicle & Truck Guides and Repair Journals. |url=https://ranwhenparked.net/what-is-nitro-methane-fuel/ |access-date=2024-05-31 |website=ranwhenparked.net |language=en-US}}</ref> During nitromethane combustion, [[nitric oxide]] (NO) is one of the major emission products along with CO{{sub|2}} and H{{sub|2}}O.<ref>{{Cite journal|last1=Shrestha|first1=Krishna Prasad|last2=Vin|first2=Nicolas|last3=Herbinet|first3=Olivier|last4=Seidel|first4=Lars|last5=Battin-Leclerc|first5=Frédérique|last6=Zeuch|first6=Thomas|last7=Mauss|first7=Fabian|date=2020-02-01|title=Insights into nitromethane combustion from detailed kinetic modeling – Pyrolysis experiments in jet-stirred and flow reactors|journal=Fuel|volume=261|pages=116349|doi=10.1016/j.fuel.2019.116349|bibcode=2020Fuel..26116349S |s2cid=208755285|issn=0016-2361|url=https://hal.archives-ouvertes.fr/hal-02320515/file/2020%20Fuel%20CH3NO2.pdf}}</ref> Nitric oxide contributes to air pollution, acid rain, and ozone layer depletion. Recent (2020) studies<ref>{{Cite journal|last1=Shrestha|first1=Krishna Prasad|last2=Vin|first2=Nicolas|last3=Herbinet|first3=Olivier|last4=Seidel|first4=Lars|last5=Battin-Leclerc|first5=Frédérique|author5-link=Frédérique Battin-Leclerc|last6=Zeuch|first6=Thomas|last7=Mauss|first7=Fabian|date=2020-02-01|title=Insights into nitromethane combustion from detailed kinetic modeling – Pyrolysis experiments in jet-stirred and flow reactors|journal=Fuel|volume=261|pages=116349|doi=10.1016/j.fuel.2019.116349|bibcode=2020Fuel..26116349S |s2cid=208755285|issn=0016-2361|url=https://hal.archives-ouvertes.fr/hal-02320515/file/2020%20Fuel%20CH3NO2.pdf}}</ref> suggest the correct stoichiometric equation for the burning of nitromethane is:

:4 CH₃NO₂ + 5 O₂ → 4 CO₂ + 6 H₂O + 4 NO

The amount of air required to burn {{convert|1|kg|lb|abbr=on}} of gasoline is {{convert|14.7|kg|lb|abbr=on}}, but only {{convert|1.7|kg|lb|abbr=on}} of air is required for 1&nbsp;kg of nitromethane. Since an engine's cylinder can only contain a limited amount of air on each stroke, 8.6 times as much nitromethane as gasoline can be burned in one stroke. Nitromethane, however, has a lower specific energy: gasoline provides about 42–44 [[megajoule|MJ]]/kg, whereas nitromethane provides only 11.3 MJ/kg.{{Citation needed|date=April 2022}} This analysis indicates that nitromethane generates about 2.3 times the power of gasoline when combined with a given amount of oxygen.{{Citation needed|date=April 2022}}

Nitromethane can also be used as a [[monopropellant]], i.e., a propellant that decomposes to release energy without added oxygen. It was first tested as rocket monopropellant in 1930s by {{ill|Luigi Crocco|it|Luigi Crocco}} fom Italian Rocket Society.<ref>{{Cite conference |last=Boyer |first=E. |last2=Kuo |first2=K. |date=January 2006 |title=Characteristics of Nitromethane for Propulsion Applications |url=https://arc.aiaa.org/doi/10.2514/6.2006-361 |conference=44th AIAA Aerospace Sciences Meeting and Exhibit |location=Reno, NV |doi=10.2514/6.2006-361 |isbn=978-1-62410-039-0 |id=AIAA 2006-361}}</ref><ref name="Ignition">{{Cite book |last=Clark |first=J. D. |url=https://archive.org/details/ignitioninformal0000clar |title=Ignition! an informal history of liquid rocket propellants |last2=Asimov |first2=Isaac |date=1972 |publisher=Rutgers University Press |isbn=978-0-8135-0725-5 |pages=[https://archive.org/details/ignitioninformal0000clar/page/9 9]-10 |url-access=registration}}</ref> There is a renewed interest in nitromethane as safer replacement of [[hydrazine]] monopropellant.<ref>{{Cite conference |last= Kurilov |first=Maxim |last2= Werling |first2=Lukas |last3= Kirchberger |first3=Christoph |date=2023 |title=Nitromethane as a Green Propellant: First Results of a Combustion Test Campaign |url=https://www.eucass.eu/doi/EUCASS2023-372.pdf |conference=Aerospace Europe Conference 2023 |doi=10.13009/EUCASS2023-372 |doi-access=free}}</ref> The following equation describes this process:

:2 CH₃NO₂ → 2 CO + 2 H₂O + H₂ + N₂

Nitromethane has a [[Laminar flame speed|laminar combustion velocity]] of approximately 0.5&nbsp;m/s, somewhat higher than gasoline, thus making it suitable for high-speed engines. It also has a somewhat higher [[Adiabatic flame temperature|flame temperature]] of about {{convert|2400|C|F}}. The high heat of vaporization of 0.56 MJ/kg together with the high fuel flow provides significant cooling of the incoming charge (about twice that of methanol), resulting in reasonably low temperatures.{{Citation needed|date=April 2022}}

Nitromethane is usually used with [[Air-fuel ratio|rich air–fuel mixtures]] because it provides power even in the absence of atmospheric oxygen. When rich air–fuel mixtures are used, hydrogen and carbon monoxide are two of the combustion products. These gases often ignite, sometimes spectacularly, as the normally very rich mixtures of the still burning fuel exits the exhaust ports. Very rich mixtures are necessary to reduce the temperature of combustion chamber hot parts in order to control pre-ignition and subsequent detonation. Operational details depend on the particular mixture and engine characteristics.{{Citation needed|date=April 2022}}

A small amount of [[hydrazine]] blended in nitromethane can increase the power output even further. With nitromethane, hydrazine forms an explosive salt that is again a monopropellant. This unstable mixture poses a severe safety hazard. The [[National Hot Rod Association]] and [[Academy of Model Aeronautics]] do not permit its use in competitions.<ref>{{cite web |url=https://www.modelaircraft.org/files/2015-2016General.pdf |title=AMA Competition Regulations 2015–2016 Part 7. Fuels |author=<!--Staff writer(s); no by-line.--> |page=24 |date=February 15, 2016 |website=www.modelaircraft.org |publisher=Academy of Model Aeronautics |access-date=April 18, 2014}}</ref>

In [[model aircraft]] and [[model car|car]] [[glow fuel]], the primary ingredient is generally [[methanol]] with some nitromethane (0% to 65%, but rarely over 30%, and 10–20% lubricants (usually [[castor oil]] and/or [[synthetic oil]])). Even moderate amounts of nitromethane tend to increase the power created by the engine (as the limiting factor is often the air intake), making the engine easier to tune (adjust for the proper air/fuel ratio).

===Former uses===

It formerly was used in the explosives industry as a component in a binary explosive formulation with ammonium nitrate and in shaped charges, and it was used as a chemical stabilizer to prevent decomposition of various halogenated hydrocarbons.<ref>{{Cite web |last=SABIC |first=Cas AardenGraduate University of Groningen Worked as a chemist in companies such as Wilmar Oleochemicals B. Vand |title=Nitromethane: An Ultimate Guide to Properties, Uses and Synthesis |url=https://safrole.com/knowledge-base/nitromethane-an-ultimate-guide-to-properties-uses-and-synthesis/ |access-date=2024-05-31 |website=Safrole |language=en-US}}</ref>

===Other===

It can be used as an explosive, when gelled with several percent of gelling agent. This type of mixture is called [[PLX]]. Other mixtures include ANNM and ANNMAl – explosive mixtures of ammonium nitrate, nitromethane and aluminium powder.

==Reactions==

===Acid-base properties===

Nitromethane is a relatively acidic [[carbon acid]]. It has a pK_a of 17.2 in [[DMSO]] solution. This value indicates an aqueous pK_a of about 11.<ref>{{cite journal|author1=Bordwell, F. G. |author2=Satish, A. V. |title=Is Resonance Important in Determining the Acidities of Weak Acids or the Homolytic Bond Dissociation Enthalpies (BDEs) of Their Acidic H-A Bonds?|journal=Journal of the American Chemical Society|volume=116|issue=20|pages=8885–8889|doi=10.1021/ja00099a004|year=1994}}</ref> It is so acidic because the anion admits an alternate, stabilizing resonance structure: [[File:Nitromethane anion resonance.jpg|center|frameless|alt=Resonance with the aci form.]]

The acid deprotonates only slowly. Protonation of the [[conjugate base]] O₂NCH₂⁻, which is nearly isosteric with [[nitrate]], occurs initially at oxygen.<ref>{{cite book|doi=10.1002/9780470166437.ch1|author1=Kramarz, K. W. |author2=Norton, J. R. |title=Progress in Inorganic Chemistry|pages=1–65|chapter=Slow Proton-Transfer Reactions in Organometallic and Bioinorganic Chemistry|year=2007|isbn=9780470166437}}

</ref>

===Organic reactions===

In [[organic synthesis]] nitromethane is employed as a one carbon [[synthon|building block]].<ref>{{ OrgSynth | author = Dauben, H. J. Jr. | author2 = Ringold, H. J. | author3 = Wade, R. H. | author4 = Pearson, D. L. | author5 = Anderson, A. G. Jr. | author6 = de Boer, T. J. | author7 = Backer, H. J. | title = Cycloheptanone | collvol = 4 | collvolpages = 221 | year = 1963 | prep = cv4p0221 }}</ref><ref>{{ OrgSynth | author = Noland, W. E. | title = 2-Nitroethanol | collvol = 4 | collvolpages = 833 | year = 1963 | prep = cv5p0833 }}</ref> Its acidity allows it to undergo deprotonation, enabling condensation reactions analogous to those of carbonyl compounds. Thus, under base catalysis, nitromethane adds to [[aldehyde]]s in 1,2-addition in the [[nitroaldol reaction]]. Some important derivatives include the pesticides [[chloropicrin]] (Cl₃CNO₂), [[beta-Nitrostyrene|beta-nitrostyrene]], and tris(hydroxymethyl)nitromethane, ((HOCH₂)₃CNO₂). Reduction of the latter gives tris(hydroxymethyl)aminomethane, (HOCH₂)₃CNH₂, better known as [[tris]], a widely used [[Buffer solution|buffer]]. In more specialized [[organic synthesis]], nitromethane serves as a Michael donor, adding to α,β-unsaturated carbonyl compounds via 1,4-addition in the [[Michael reaction]].

Nitromethane is a popular solvent in organic and electroanalytical chemistry. It can be purified by cooling below its freezing point, washing the solid with cold [[diethyl ether]], followed by distillation.<ref>{{cite journal =Coetzee, J. F. Chang, T.H.| title= Recommended Methods for the Purification of Solvents and Tests for Impurities: Nitromethane | journal = [[Pure ]] | year = 1986 | volume = 58 | pages = 1541–1545 | url = http://www.iupac.org/publications/pac/1986/pdf/5811x1541.pdf }}</ref>

==Safety==

Nitromethane has a modest acute toxicity. [[LD50]] (oral, rats) is 1210±322&nbsp;mg/kg.<ref name=Markofsky/>

Nitromethane is "reasonably anticipated to be a human carcinogen" according to a U.S. government report.<ref>{{Cite web |date=December 21, 2021 |title=National Toxicology Program 15th Report on Carcinogens |url=https://ntp.niehs.nih.gov/sites/default/files/ntp/roc/content/profiles/nitromethane.pdf |url-status=live |archive-url=https://web.archive.org/web/20231002221739/https://ntp.niehs.nih.gov/sites/default/files/ntp/roc/content/profiles/nitromethane.pdf |archive-date=October 2, 2023 |access-date=May 30, 2024 |website=National Toxicology Program U.S. Department of Health and Human Services}}</ref>

=== Explosive properties ===

Nitromethane was not known to be a high [[explosive]] until a railroad [[tank car]] loaded with it exploded on {{#dateformat:June 1, 1958}}.<ref>{{cite web | url = http://www.blet602.org/Historic_accidents/Mt.%20Pulaski_6.1.1958.pdf | author = Interstate Commerce Commission | work = Ex Parte No 213 | title = Accident Near Mt. Pulaski, ILL |archiveurl=https://web.archive.org/web/20201101034350/http://www.blet602.org/Historic_accidents/Mt.%20Pulaski_6.1.1958.pdf|archivedate=1 November 2020}}</ref> After much testing{{citation needed|date=February 2024}}, it was realized that nitromethane was a more energetic high explosive than [[Trinitrotoluene|TNT]]{{citation needed|date=February 2024}}, although TNT has a higher [[Detonation velocity|velocity of detonation]] (VoD) and [[brisance]]{{citation needed|date=February 2024}}. Both of these explosives are oxygen-poor, and some benefits are gained from mixing with an [[oxidizer]], such as [[ammonium nitrate]]. Pure nitromethane is an insensitive explosive with a VoD of approximately {{convert|6400|m/s|ft/s|abbr=on}}, but even so inhibitors may be used to reduce the hazards. The tank car explosion was speculated{{citation needed|date=February 2024}} to be due to [[Adiabatic process|adiabatic]] compression, a hazard common to all liquid explosives. This is when small entrained air bubbles compress and superheat with rapid rises in pressure. It was thought that an operator rapidly snapped shut a valve creating a "[[water hammer|hammer-lock]]" pressure surge.{{Citation needed|date=April 2022}}

If mixed with [[ammonium nitrate]], which is used as an oxidizer, it forms an explosive mixture known as [[ANFO#ANNM|ANNM]].

Nitromethane is used as a model explosive, along with TNT. It has several advantages as a model explosive over TNT, namely its uniform density and lack of solid post-detonation species that complicate the determination of equation of state and further calculations.

Nitromethane reacts with solutions of sodium hydroxide or methoxide in alcohol to produce an insoluble salt of nitromethane. This substance is a sensitive explosive which reverts to nitromethane under acidic conditions and decomposes in water to form another explosive compound, sodium methazonate, which has a reddish-brown color:

:2 CH₃NO₂ + NaOH → HON=CHCH=NO₂Na + 2 H₂O

Nitromethane's reaction with solid sodium hydroxide is [[Hypergolic propellant|hypergolic]].

*[[Dinitromethane]]

*[[Model engine]]

*[[Trinitromethane]]

*[[Tetranitromethane]]

*[[RE factor]]

{{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 }}

* [http://www.dragtimes.com/Nitromethane-Drag-Racing-Top-Fuel-Soup-of-Choice.html ]

* [https://www.cdc.gov/niosh/npg/npgd0457.html CDC – NIOSH Pocket Guide to Chemical Hazards]

{{Authority control}}

[[Category:Nitroalkanes]]

[[Category:Organic compounds with 1 carbon atom]]