Nitromethane
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| Nitromethane | |
|---|---|
| Image:Nitromethane2.png | |
| General | |
| Systematic name | nitromethane |
| Other names | nitrocarbol |
| Molecular formula | CH3NO2 |
| SMILES | C[N+]([O-])=O |
| Molar mass | 61.04 g/mol |
| Appearance | colorless liquid |
| CAS number | [200-876-6] |
| Properties | |
| Density and phase | 1.138 g/cm3, liquid |
| Solubility in water | miscible |
| Melting point | -29 °C (244.15 K) |
| Boiling point | 100-103 °C (373-376 K) |
| Acidity (pKa) | 10.2 |
| Viscosity | ? cP at ? °C |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Flammable, harmful |
| NFPA 704 | Template:Nfpa |
| Flash point | 35 °C |
| R/S statement | R: Template:R5 Template:R10 Template:R22 S: Template:S41 |
| RTECS number | PA9800000 |
| Related compounds | |
| Related nitro compounds | nitroethane |
| Related compounds | methyl nitrite methyl nitrate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Nitromethane is an organic compound with the chemical formula CH3NO2. It is the simplest organic nitro compound. It is a slightly viscous, highly 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 pharmaceuticals, pesticides, explosives, fibers, and coatings. It also finds use as a racing fuel.
Contents |
Reactions
The weak acidicity of nitromethane allows it to undergo reactions analogous to those of carbonyl compounds:
- Nitromethane can add to aldehydes in 1,2-addition in the nitroaldol reaction
- Nitromethane can act as a Michael donor, adding to α,β-unsaturated carbonyl compounds by 1,4-addition in the Michael reaction
Use as an engine fuel
Nitromethane is used as a fuel in racing, particularly drag racing, to provide more power. In this context, it is commonly referred to as "nitro" or "fuel".
The oxygen in the molecular structure of nitromethane enables it to burn with much less atmospheric oxygen in comparison to hydrocarbons such as gasoline. Part of the oxygen needed for combustion is carried by nitromethane itself. 14.6 kg of air are needed to burn one kg of gasoline, but only 1.7 kg of air are needed to burn one kg of nitromethane. Since an engine’s cylinder can only contain a limited amount of air on each stroke, 8.7 times more nitromethane than gasoline can be burned in one stroke. However, nitromethane has a lower energy density. Gasoline provides 18,000 BTU/pound (42 MJ/kg). Nitromethane provides only 5,000 BTU/pound (12 MJ/kg). [1]. The net result is that nitromethane provides 2.4 times more power per stroke than gasoline.
The flamefront of combusting nitromehane does not move as quickly as it does for gasoline, meaning that there is not enough time to burn all the nitromethane in the cylinder when the engine is running at high RPM. When the exhaust valves open, nitromethane flows out through the exhaust pipes where it is ignited producing the visible flames characteristic of dragsters and funny cars.
In addition, model aircraft and car fuel contains from 0% to 65% nitromethane. It has also been used as a model rocket fuel.
Explosive properties
Nitromethane was not known to be an explosive until the 1950s, when a whole railroad tanker car of it exploded, leaving a huge crater. Much testing later it was realized that nitromethane was a more energetic high explosive than TNT. However TNT has a higher velocity of detonation and brisance (shattering power against hard targets). Both of these explosives are oxygen poor and some benefits are gained from mixing with an oxidizer, such as ammonium nitrate. One graphic example of this was the use of nitromethane and ammonium nitrate on the Alfred P. Murrah Federal Building at Oklahoma City. Pure nitromethane is a very insensitive explosive, but even so inhibitors may be used to reduce the hazards. The tank car explosion was speculated to be due to 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 'hammer-lock' pressure surge. Nitromethane can be sensitized by adding a base to raise the pH.
See also
Adiabatic flame temperature for a thermodynamic calculation of the flame temperature of nitromethane.ca:Template:Chembox de:Nitromethan it:Nitrometano pl:Nitrometan