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| Names | |||
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| IUPAC name Nitromethane | |||
| Preferred IUPAC name Nitromethane[1] | |||
| Other names Nitrocarbol | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| ECHA InfoCard | 100.000.797 | ||
| KEGG |
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| RTECS number |
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| UNII | |||
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| Properties | |||
| CH3NO2 | |||
| Molar mass | 61.04 g/mol | ||
| Appearance | colorless, oily liquid[2] | ||
| Odor | Light, fruity[2] | ||
| Density | 1.1371 g/cm3 (20 °C)[3] | ||
| Melting point | −28.7 °C (−19.7 °F; 244.5 K)[3] | ||
| Boiling point | 101.2 °C (214.2 °F; 374.3 K)[3] | ||
| Critical point (T,P) | 588 K, 6.0 MPa[4] | ||
| ca. 10 g/100 mL | |||
| Solubility | miscible indiethyl ether,acetone,ethanol,methanol[3] | ||
| Vapor pressure | 28 mmHg (20 °C)[2] | ||
| Acidity (pKa) | |||
| −21.0·10−6 cm3/mol[7] | |||
| Thermal conductivity | 0.204 W/(m·K) at 25 °C[8] | ||
Refractive index (nD) | 1.3817 (20 °C)[3] | ||
| Viscosity | 0.63cP at 25 °C[8] | ||
| 3.46[9] | |||
| Explosive data | |||
| Shock sensitivity | Low | ||
| Friction sensitivity | Low | ||
| Detonation velocity | 6400 m/s | ||
| Thermochemistry[10] | |||
| 106.6 J/(mol·K) | |||
Std molar entropy(S⦵298) | 171.8 J/(mol·K) | ||
Std enthalpy of formation(ΔfH⦵298) | −112.6 kJ/mol | ||
Gibbs free energy(ΔfG⦵) | −14.4 kJ/mol | ||
Std enthalpy of combustion(ΔcH⦵298) | -709 kJ/mol | ||
Enthalpy of fusion(ΔfH⦵fus) | 9.7 kJ/mol | ||
Enthalpy of vaporization(ΔfHvap) | 38.3 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Flammable, health hazard | ||
| GHS labelling: | |||
    | |||
| Danger | |||
| H203,H226,H301,H331,H351 | |||
| P210,P261,P280,P304+P340,P312,P370+P378,P403+P233 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 35[9] °C (95 °F; 308 K) | ||
| 418[9] °C (784 °F; 691 K) | |||
| Explosive limits | 7–22%[9] | ||
Threshold limit value (TLV) | 20 ppm[9] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 940 mg/kg (oral, rat) 950 mg/kg (oral, mouse)[11] | ||
LDLo (lowest published) | 750 mg/kg (rabbit, oral) 125 mg/kg (dog, oral)[11] | ||
LCLo (lowest published) | 7087 ppm (mouse, 2 h) 1000 ppm (monkey) 2500 ppm (rabbit, 12 h) 5000 ppm (rabbit, 6 h)[11] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 100 ppm (250 mg/m3)[2] | ||
REL (Recommended) | none[2] | ||
IDLH (Immediate danger) | 750 ppm[2] | ||
| Related compounds | |||
Relatednitro compounds | nitroethane | ||
Related compounds | methyl nitrite methyl nitrate | ||
| Supplementary data page | |||
| Nitromethane (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Nitromethane, sometimes shortened to simply "nitro", is anorganic compound with the chemical formulaCH3NO2. It is the simplest organicnitro 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 inorganic synthesis, it is used widely in the manufacture of pesticides, explosives, fibers, and coatings.[12] Nitromethane is used as a fuel additive in variousmotorsports and hobbies, e.g.Top Fueldrag racing and miniatureinternal combustion engines inradio control,control line andfree flight model aircraft.
Nitromethane is produced industrially by combiningpropane andnitric acid in the gas phase at 350–450 °C (662–842 °F). Thisexothermic reaction produces the four industrially significant nitroalkanes: nitromethane,nitroethane,1-nitropropane, and2-nitropropane. The reaction involves free radicals, including the alkoxyl radicals of the typeCH3CH2CH2O, which arise viahomolysis of the corresponding nitriteester. These alkoxy radicals are susceptible to C—C fragmentation reactions, which explains the formation of a mixture of products.[12]
It can also be prepared by other methods that are of instructional value. The reaction ofsodium chloroacetate withsodium nitrite inaqueous solution produces this compound, along withsodium chloride andsodium bicarbonate:[13]
The dominant use of the nitromethane is as a precursor reagent. A major derivative ischloropicrin (CCl3NO2), a widely used pesticide. It condenses withformaldehyde (Henry reaction) to eventually givetris(hydroxymethyl)aminomethane ("tris"), a widely used buffer and ingredient inalkyd resins.[12]
The major application is as a stabilizer in chlorinated solvents. As an organic solvent, nitromethane has an unusual combination of properties: highly polar (εr = 36 at 20 °C and μ = 3.5 Debye) butaprotic and weakly basic. This combination makes it useful for dissolving positively charged, strongly electrophilic species. It is a solvent for acrylatemonomers, such ascyanoacrylates (more commonly known as "super-glues").[12]
Although a minor application in terms of volume,[12] nitromethane also is used as a fuel or fuel additive for sports and hobby. For some applications, it is mixed with methanol in racing cars, boats, and model engines.
Nitromethane is used as a fuel in motor racing, particularlydrag racing, as well as forradio-controlled model power boats,cars,planes andhelicopters. 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.[14]
Theoxygen content of nitromethane enables it to burn with much less atmospheric oxygen than conventional fuels.[15] During nitromethane combustion,nitric oxide (NO) is one of the major emission products along with CO2 and H2O.[16] Nitric oxide contributes to air pollution, acid rain, and ozone layer depletion. Recent (2020) studies[17] suggest the correct stoichiometric equation for the burning of nitromethane is:
The amount of air required to burn 1 kg (2.2 lb) of gasoline is 14.7 kg (32 lb), but only 1.7 kg (3.7 lb) of air is required for 1 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 42–44MJ/kg, whereas nitromethane provides only 11.3 MJ/kg.[citation needed] This analysis indicates that nitromethane generates about 2.3 times the power of gasoline when combined with a given amount of oxygen.[citation needed]
Nitromethane can also be used as amonopropellant, i.e., a propellant that decomposes to release energy without added oxygen. It was first tested as rocket monopropellant in 1930s byLuigi Crocco [it] from the Italian Rocket Society.[18][19] There is a renewed interest in nitromethane as safer replacement ofhydrazine monopropellant.[20] The following equation describes this process:
Nitromethane has alaminar combustion velocity of approximately 0.5 m/s, somewhat higher than gasoline, thus making it suitable for high-speed engines. It also has a somewhat higherflame temperature of about 2,400 °C (4,350 °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]
Nitromethane is usually used withrich 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]
A small amount ofhydrazine 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. TheNational Hot Rod Association andAcademy of Model Aeronautics do not permit its use in competitions.[21]
Inmodel aircraft andcarglow fuel, the primary ingredient is generallymethanol with some nitromethane (0% to 65%, but rarely over 30%, and 10–20% lubricants (usuallycastor oil and/orsynthetic 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).
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.[22]
It can be used as an explosive, when gelled with several percent of gelling agent. This type of mixture is calledPLX. Other mixtures include ANNM and ANNMAl – explosive mixtures of ammonium nitrate, nitromethane andaluminium powder.
Nitromethane is a relatively acidiccarbon acid. It has a pKa of 17.2 inDMSO solution. This value indicates an aqueous pKa of about 11.[23] It is so acidic because the anion admits an alternate, stabilizing resonance structure:
The acid deprotonates only slowly. Protonation of theconjugate baseO2NCH−2, which is nearly isosteric withnitrate, occurs initially at oxygen.[24]
Inorganic synthesis nitromethane is employed as a one carbonbuilding block.[25][26] Its acidity allows it to undergo deprotonation, enabling condensation reactions analogous to those of carbonyl compounds, and acting as aMichael donor. Thus, under base catalysis, nitromethane adds toaldehydes in 1,2-addition in thenitroaldol reaction and condenses with itself to makemethazonic acid [de].
Some important derivatives include thepesticidechloropicrinCl3CNO2, theslimicideβ-bromo-β-nitrostyrene [wd] (viaβ-nitrostyrene), and thebiocidetris(hydroxymethyl)nitromethane [wd](HOCH2)3CNO2. Reduction of the latter gives tris(hydroxymethyl)aminomethane,(HOCH2)3CNH2, better known astris, a widely usedbuffer.[12]
Nitromethane is a popular solvent in organic and electroanalytical chemistry. It can be purified by cooling below its freezing point, washing the solid with colddiethyl ether, followed by distillation.[27]
Nitromethane has a modest acute toxicity.LD50 (oral, rats) is 1210±322 mg/kg.[12]
Nitromethane is "reasonably anticipated to be a human carcinogen" according to a U.S. government report.[28] In the United States, Nitromethane is regulated under the Department of Homeland Security, specifically under the Chemical Facilities Anti-Terrorism Standards (CFATS).[29] Their program ensures that high-risk facilities take appropriate security measures to reduce overall risk associated with certain chemicals.[29] The Department of Homeland Security considers chemicals such as Nitromethane to be "chemicals of interest" (COI) due to their hazardous nature.[29] Due to this, CFATS requires specific protocols to be taken for marking, labeling, and transporting this material.[30] Additionally, within any facility that possesses over 42 gallons or more of Nitromethane must report and implement CFATS security measures accordingly.[29]
Nitromethane was not known to be a highexplosive until a railroadtank car loaded with it exploded onJune 1, 1958.[31] After much testing[citation needed], it was realized that nitromethane was a more energetic high explosive thanTNT[citation needed], although TNT has a highervelocity of detonation (VoD) andbrisance[citation needed]. Both of these explosives are oxygen-poor, and some benefits are gained from mixing with anoxidizer, such asammonium nitrate. Large amounts of these explosives were used inOperation Plowshare that mainly focused on nuclear explosions.
Pure nitromethane is an insensitive explosive with a VoD of approximately 6,400 m/s (21,000 ft/s), but even so inhibitors may be used to reduce the hazards. The tank car explosion was speculated[citation needed] to be due toadiabatic 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 "hammer-lock" pressure surge.[citation needed]
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:
Nitromethane's reaction with solid sodium hydroxide ishypergolic.
Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA),nitromethane is a hazardous chemical substance that has a federal reportable quantity of 1000 pounds. Any release of this chemical at or above this amount has to be reported within a 24-hour period.[32]
Data from the United States National Health and Nutrition Examination Survey(NHANES) about the chemical states that Nitromethane has been detected in a lot of blood sample tests from smokers. Analyzing this data found that smoking half a pack of cigarettes per day could cause a 150ng/L increase in nitromethane inside of your blood stream compared to non smokers.[33]
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