Nitromethane

Nitromethane

Names
IUPAC name Nitromethane
Other names Nitro fuel Nitrocarbol
Identifiers
Jmol-3D images	Image
SMILES C[N+](=O)[O-]
Properties
Chemical formula	CH3NO2
Molar mass	61.04 g/mol
Appearance	Colorless liquid
Odor	Fruity, pungent
Density	1.1371 g/cm3 (20 °C)
Melting point	−28.38 °C (−19.08 °F; 244.77 K)
Boiling point	101.19 °C (214.14 °F; 374.34 K)
Solubility in water	9.5 ml/100 ml (1.8%) (20 °C) 2.1% (20 °C) 7.6% (70 °C)
Solubility	Reacts with amines and other bases Miscible with acetone, carbon tetrachloride, diethyl ether, ethanol, methanol Immiscible with alkanes, ethylene glycol, glycerol
Vapor pressure	28 mmHg (20 °C)
Acidity (pKa)	17.2 (DMSO)
Thermochemistry
Hazards
Safety data sheet	Sigma-Aldrich
Flash point	35 °C (95 °F; 308 K)
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	940 mg/kg (rat, oral) 950 mg/kg (mouse, oral)
Related compounds
Related compounds	Nitroethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Nitromethane (NM) is an organic compound with the chemical formula CH₃NO₂. It is the simplest organic nitro compound.

Properties

Chemical

Nitromethane burns when ignited in air, releasing combustion gasses. It burns with a gray flame.

4 CH₃NO₂ + 3 O₂ → 4 CO₂ + 6 H₂O + 2 N₂

Nitromethane reacts violently with bases, such as sodium hydroxide or ammonia/amines, forming nitronate salts, which are highly sensitive to shock and impact, moreso when dry.

NaOH + CH₃NO₂ → NaCH₂=NO₂ + H₂O

The heat generated by the reaction can even ignite the nitromethane.

Nitromethane will not react with strong oxidizers like manganese heptoxide. This was observed by many SM members, such as Rhodanide and Tdep.

Physical

Nitromethane is a colorless, slightly viscous, highly polar liquid. It is poorly soluble in water, but miscible with other organic solvents, such as alcohols. It freezes at −29 °C and boils at around 100 °C.

Nitromethane will form a heteroazeotrope with water, consisting of 76.4% NM by weight, which boils at 83.6°C.

Availability

Nitromethane is often available from lab suppliers at a price of around $100/L. It is also sold in many places locally for use in RC fuel, either pure or as a mixture with methanol and (castor) oil. Separation of the nitromethane from this mixture can be quite difficult, but it is achievable with good technique.

To separate nitromethane from RC fuel, you will first have to fractionally distill the RC fuel. The first fraction that will distill is the NM-MeOH azeotrope, containing 9% NM at 64.6 °C, which is close to the boiling point of pure methanol at 64.7 °C, meaning that unless you have a very long column or a very efficient fractionating system, you will practically distill the MeOH along with the NM-MeOH azeotrope. However, if your RC fuel has a high NM percentage, the leftover NM will distill next, leaving the castor oil and other high boiling point fractions in the flask. Separation of NM from the NM-MeOH azeotrope can be done by adding a neutral/acidic salt or acid to the mixture, which should salt out the NM from the MeOH, though this doesn't always work. The separated NM is purified via distillation. The NM obtained this way will still have some methanol present, and removing the last bits of methanol is not necessary for most purposes, as they do not interfere with reactions.

Preparation

Nitromethane is produced industrially by treating propane with nitric acid at 350–450 °C. This exothermic reaction produces the four industrially significant nitroalkanes: nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane. Nitromethane is then separated via fractional distillation.

Another method involves the reaction between sodium chloroacetate and sodium nitrite in aqueous solution:

ClCH₂COONa + NaNO₂ + H₂O → CH₃NO₂ + NaCl + NaHCO₃

Projects

• Methyl nitroacetate synthesis
• RC fuel
• Make ANNM
• Facile synthesis of hydroxylammonium salts
• Dissolve superglue

Handling

Safety

Nitromethane is quite inflammable so it should not be handled around open flames or other ignition sources. Pure nitromethane is a powerful explosive, though it is rather insensitive and difficult to initiate. Gloves should be worn when working with nitromethane to prevent accidental skin contact.

Storage

Nitromethane must be kept in closed bottles away from any ignition sources and away from ammonia and other amines.

Disposal

Nitromethane can be safely burned, though it's best to mix it with another fuel first, like ethanol, as the flame is nearly invisible.

For the inexperienced chemist, the text below shows the dangers of handling nitromethane without knowing its properties:

Aqueous solution of sodium hydroxide will readily hydrolyze it to methanol, which can be safely burned.

• No. The chemistry of C-Nitro compounds is very different to nitrite and nitrate esters. Hydrolysis of nitromethane by sodium hydroxide is messy and exothermic through potentially explosive thermal and shock sensitive salts/compounds ultimately to carbonate and ammonia. Bases are sensitisers of nitromethane. This is not a good plan. Marvin (talk) 12:42, 9 July 2016 (UTC)

References

Relevant Sciencemadness threads

• Nitromethane extraction
• nitromethane purity for ANNM compositions
• old nitromethane
• Manganese Heptoxide + Nitromethane = Nothing?!