Molecules: You'd better learn to live with them.
Nitromethane has some odd properties, due to the singular weirdness of the nitro group.
The electron-withdrawing nature of the group makes it a decent acid; in neutral (i.e., pH 7) water, about 1 in 1000 molecules of nitromethane will have a formal negative charge on the carbon and exist as CH2NO2-. There aren't many of these "carbon acids," and their properties make them useful in organic synthesis.
The "nitro" part of nitromethane doesn't disappoint if you associate the prefix/word with nitrous oxide and TNT, either; nitromethane is a very energetic compound and can be explosive (it was used in the Oklahoma City bombing). It's relatively insensitive - especially compared to things like nitroglycerine and TNT, which aren't likely to find their way near me anytime soon. Still, the explosiveness of nitromethane was discovered by accident, as this drag-racing site notes:
Joe Fette, a former vice president and general manager of Angus Chemical, worked intimately with the nitromethane departments, and remembers when the discovery was made. "The condition first came about by accident," says Fette. "Luckily, it was an accident where nobody was killed. But nitromethane used to be shipped in tank cars before this condition was known. Two separate accidents within a year of each other stopped that. The tank cars exploded, leaving holes 800ft wide and 300ft deep. Luckily, these were out in unpopulated areas. What happened is that the fuel was compressed when it slammed into the other car (as the train crashed). There were also rumors of power lines being around, although that was never proven."
One key element to explosives (and certain specialty fuels) is that they contain their own oxidizer; nitromethane can actually burn in the absence of air, yielding nitrogen, hydrogen, carbon monoxide, and water vapor. There's still energy to be obtained from the CO and H2, though; with sufficient oxygen, it will go all the way to CO2, nitrogen, and water. This is the case in drag racing and model airplanes; nitromethane contains about 25% of the energy of gasoline but takes only about an eighth the oxygen to burn completely. This means that engines can run much "richer" (i.e., with less air in the cylinder); hence the use in dragsters.
I'm kind of surprised that any Joe Sixpack with a model plane can still get hold of it.
Comments
Wasn't NitroMethane one of the candidates for the "liquid explosive" the TSA went apeshit about last year ? It seems reasonably stable.
What does it smell ? What does it taste ?
Posted by: _Arthur | April 4, 2007 9:41 PM
I use it in my model car. I'm not sure what it smells like by itself, as it is mixed with methanol and synthetic oil, but you can instantly recognise the smell of it when it burns in one of the tiny engines used. There is a good article in Wikipedia discussing the various modes of combustion of nitromethane in combustion engines. Just search it on Wiki
Posted by: Russ | April 5, 2007 12:22 PM
While nitro is available to RC "joe sixpacks" it is diluted with methanol. Even 20% methanol greatly decreases the detonation ability of nitromethane. Pure nitromethane is government regulated.
Posted by: Chuck | January 21, 2009 10:26 PM