Nitromethane
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Names | |||
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IUPAC name
Nitromethane
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Preferred IUPAC name
Nitromethane[1] | |||
Other names
Nitrocarbol
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Identifiers | |||
3D model (
JSmol ) |
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ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard
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100.000.797 | ||
KEGG | |||
PubChem CID
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RTECS number
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UNII | |||
CompTox Dashboard (EPA)
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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 in diethyl ether, acetone, ethanol, methanol[3] | ||
Vapor pressure | 28 mmHg (20 °C)[2] | ||
Acidity (pKa) | |||
-21.0·10−6 cm3/mol[7] | |||
Thermal conductivity
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0.204 W/(m·K) at 25 °C[8] | ||
Refractive index (nD)
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1.3817 (20 °C)[3] | ||
Viscosity | 0.63 cP at 25 °C[8] | ||
3.46[9] | |||
Thermochemistry[10] | |||
Heat capacity (C)
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106.6 J/(mol·K) | ||
Std molar
entropy (S⦵298) |
171.8 J/(mol·K) | ||
Std enthalpy of (ΔfH⦵298)formation |
-112.6 kJ/mol | ||
Gibbs free energy (ΔfG⦵)
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-14.4 kJ/mol | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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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
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7–22%[9] | ||
Threshold limit value (TLV)
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20 ppm[9] | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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940 mg/kg (oral, rat) 950 mg/kg (oral, mouse)[11] | ||
LDLo (lowest published)
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750 mg/kg (rabbit, oral) 125 mg/kg (dog, oral)[11] | ||
LCLo (lowest published)
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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)
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TWA 100 ppm (250 mg/m3)[2] | ||
REL (Recommended)
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none[2] | ||
IDLH (Immediate danger) |
750 ppm[2] | ||
Related compounds | |||
Related
nitro compounds |
nitroethane | ||
Related compounds
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methyl nitrite methyl nitrate | ||
Supplementary data page | |||
Nitromethane (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Nitromethane, sometimes shortened to simply "nitro", is an
Preparation
Nitromethane is produced industrially by combining
Laboratory methods
It can be prepared in other methods that are of instructional value. The reaction of
Uses
The principal use of nitromethane is as a stabilizer for chlorinated solvents, which are used in dry cleaning, semiconductor processing, and degreasing. It is also used most effectively as a solvent or dissolving agent for acrylate monomers, such as cyanoacrylates (more commonly known as "super-glues").[12] It is also used as a fuel in some forms of racing. 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.
As an organic solvent, it is considered to be highly polar (εr = 36 at 20 °C and μ = 3.5 Debye) but is aprotic and possesses very low Lewis basicity. Thus, it is a rare example of a polar solvent that is also weakly coordinating. This makes it useful for dissolving positively charged, strongly electrophilic species. However, its relatively high acidity and explosive properties (see below) limit its applications.
Reactions
Acid-base properties
Nitromethane is a relatively acidic
The acid deprotonates only slowly. Protonation of the
Organic reactions
In
As an engine fuel
Nitromethane is used as a fuel in motor racing, particularly
The oxygen content of nitromethane enables it to burn with much less atmospheric oxygen than conventional fuels. During nitromethane combustion, nitric oxide (NO) is one of the major emission products along with CO2 and H2O.[18] Nitric oxide contributes to air pollution, acid rain, and ozone layer depletion. Recent (2020) studies[19] 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 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 42–44
Nitromethane can also be used as a monopropellant, i.e., a propellant that decomposes to release energy without added oxygen. The following equation describes this process:
- 2 CH3NO2 → 2 CO + 2 H2O + H2 + N2
Nitromethane has a laminar 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 higher flame 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 with
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.[20]
In model aircraft and 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).
Explosive properties
Nitromethane was not known to be a high
If mixed with ammonium nitrate, which is used as an oxidizer, it forms an explosive mixture known as 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.
Nitromethane exhaust
Exhaust gas from an internal combustion engine whose fuel includes nitromethane will contain nitric acid vapour, which is corrosive, and when inhaled causes a muscular reaction making it impossible to breathe. The condensed nitric acid-based residue left over in a glow-fueled model engine after a model-flight session can also corrode their internal components, usually mandating use of a combination of kerosene to neutralize the residual nitric acid, and an "after-run oil" (often the lower-viscosity "air tool oil" variety of a popular preservative oil) for lubrication to safeguard against such damage, when such an engine is placed into storage.
Purification
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.[22]
See also
- Top Fuel
- Adiabatic flame temperature, a thermodynamic calculation of the flame temperature of nitromethane
- Dinitromethane
- Model engine
- Trinitromethane
- Tetranitromethane
- RE factor
References
- ISBN 978-0-85404-182-4.)
{{cite book}}
: CS1 maint: DOI inactive as of April 2024 (link - ^ a b c d e f NIOSH Pocket Guide to Chemical Hazards. "#0457". National Institute for Occupational Safety and Health (NIOSH).
- ^ a b c d e Haynes, p. 3.414
- ^ Haynes, p. 6.69
- ^ Haynes, p. 5.94
- ^ Reich, Hans. "Bordwell pKa table: "Nitroalkanes"". University of Wisconsin Chemistry Department. Retrieved 27 January 2022.
- ^ Haynes, p. 3.576
- ^ a b Haynes, p. 6.231
- ^ a b c d e Haynes, p. 15.19
- ^ Haynes, p. 5.20
- ^ a b c "Nitromethane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- ^ ISBN 978-3527306732.
- ^ Whitmore, F. C.; Whitmore, M. G. (1941). "Nitromethane". Organic Syntheses; Collected Volumes, vol. 1, p. 401.
- .
- ISBN 9780470166437.
- ^ Dauben, H. J. Jr.; Ringold, H. J.; Wade, R. H.; Pearson, D. L.; Anderson, A. G. Jr.; de Boer, T. J.; Backer, H. J. (1963). "Cycloheptanone". Organic Syntheses; Collected Volumes, vol. 4, p. 221.
- ^ Noland, W. E. (1963). "2-Nitroethanol". Organic Syntheses; Collected Volumes, vol. 4, p. 833.
- S2CID 208755285.
- S2CID 208755285.
- ^ "AMA Competition Regulations 2015–2016 Part 7. Fuels" (PDF). www.modelaircraft.org. Academy of Model Aeronautics. February 15, 2016. p. 24. Retrieved April 18, 2014.
- ^ Interstate Commerce Commission. "Accident Near Mt. Pulaski, ILL" (PDF). Ex Parte No 213. Archived from the original (PDF) on 1 November 2020.
- S2CID 95631774.
Cited sources
- Haynes, William M., ed. (2011). ISBN 978-1439855119.