Methanol Molecule
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Chemical and Physical Properties of the Methanol Molecule
Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol (ethyl alcohol). At room temperature it is a polar liquid and is used as an antifreeze, solvent, fuel, and as a denaturant for ethyl alcohol. It is also used for producing biodiesel via transesterification reaction.
Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria. As a result, there is a small fraction of methanol vapor in the atmosphere. Over the course of several days, atmospheric methanol is oxidized by oxygen with the help of sunlight to carbon dioxide and water.
Methanol burns in air forming carbon dioxide and water:
- 2 CH3OH + 3 O2 ---> 2 CO2 + 4 H2O
A methanol flame is almost colorless, causing an additional safety hazard around open methanol flames.
Uses
Because of its poisonous properties, methanol is frequently used as a denaturant additive for ethanol manufactured for industrial uses this addition of a poison economically exempts industrial ethanol from the rather significant 'liquor' taxes that would otherwise be levied as it is the essence of all potable alcoholic beverages. Methanol is often called wood alcohol because it was once produced chiefly as a byproduct of the destructive distillation of wood. It is now produced synthetically by a multi-step process: natural gas and steam are reformed in a furnace to produce hydrogen and carbon monoxide; then, hydrogen and carbon monoxide gases react under pressure in the presence of a catalyst.
An entire methanol economy, based on methanol as a primary energy-storage medium and fuel, has been seriously proposed.
Methanol is a common laboratory solvent. It is especially useful for HPLC and UV/VIS spectroscopy due to its low UV cutoff.Feedstock
The largest use of methanol by far, is in making other chemicals. About 40% of methanol is converted to formaldehyde, and from there into products as diverse as plastics, plywood, paints, explosives, and permanent press textiles.
Also in early 1970s Methanol to gasoline process was developed by Mobil, which produces gasoline ready for use in vehicles. One such industrial facility was built in New Zealand in the 1980s. In the 1990s, large amounts of methanol were used in the United States to produce the gasoline additive methyl tert-butyl ether (MTBE), though leakage has led to many states banning it. In addition to direct use as a fuel, methanol (or less commonly, ethanol) is used as a component in the transesterification of triglycerides to give a form of biodiesel.
Other chemical derivatives of methanol include dimethyl ether, which has replaced chlorofluorocarbons as an aerosol spray propellant, and acetic acid.
Automotive fuel
Methanol is used on a limited basis to fuel internal combustion engines, mainly by virtue of the fact that it is not nearly as flammable as gasoline. Pure methanol is required by rule to be used in Champcars, USAC sprint cars (as well as midgets, modifieds, etc.), and other dirt track series such as World of Outlaws. Methanol is also used in radio controlled model airplanes (required in the "glow-plug" engines that primarily power them), cars and trucks. Drag racers and mud racers also use methanol as their primary fuel source. Methanol is required with a supercharged engine in a Top Alcohol Dragster and, until the end of the 2005 season, all vehicles in the Indianapolis 500 had to run methanol. Mud racers have mixed methanol with gasoline and nitrous oxide to produce more power than gasoline and nitrous oxide alone.
One of the drawbacks of methanol as a fuel is its corrosivity to some metals, including aluminium.
When produced from wood or other organic materials, the resulting organic methanol (bioalcohol) has been suggested as renewable alternative to petroleum-based hydrocarbons. However, one cannot use pure methanol in modern petroleum cars without modification, due to potential damage to metal piping and rubber seals.
Other applications
Methanol is a traditional denaturant for ethanol, thus giving the term methylated spirit.Methanol is also used as a solvent, and as an antifreeze in pipelines and windshield washer fluid.In some wastewater treatment plants, a small amount of methanol is added to wastewater to provide a food source of carbon for the denitrifying bacteria, which convert nitrates to nitrogen.During World War II, methanol was used as a fuel in several German military rocket designs, under name M-Stoff, and in a mixture as C-Stoff.Methanol is used as a denaturing agent in polyacrylamide gel electrophoresis.Direct-methanol fuel cells are unique in their low temperature, atmospheric pressure operation, allowing them to be miniaturized to an unprecedented degree. This, combined with the relatively easy and safe storage and handling of methanol may open the possibility of fuel cell-powered consumer electronics, such as for laptop computers.[1]
Health and safety
Methanol is toxic by two mechanisms. Firstly, methanol (whether it enters the body by ingestion, inhalation, or absorption through the skin) can be fatal due to its CNS depressant properties in the same manner as ethanol poisoning. Secondly, it is toxic by its breakdown (toxication) by the enzyme alcohol dehydrogenase in the liver by forming formic acid and formaldehyde which cause permanent blindness by destruction of the optic nerve.[2] Fetal tissue will not tolerate methanol. Dangerous doses will build up if a person is regularly exposed to vapors or handles liquid without skin protection. If methanol has been ingested, a doctor should be contacted immediately. The usual fatal dose is 100-125 mL (4 fl oz). Toxic effects take hours to start, and effective antidotes can often prevent permanent damage. This is treated using ethanol or fomepizole.[3] Either of these drugs acts to slow down the action of alcohol dehydrogenase on methanol by means of competitive inhibition, so that it is excreted by the kidneys rather than being transformed into toxic metabolites.
The initial symptoms of methanol intoxication are those of central nervous system depression: headache, dizziness, nausea, lack of coordination, confusion, drowsiness, and with sufficiently large doses, unconsciousness and death. The initial symptoms of methanol exposure are usually less severe than the symptoms resulting from the ingestion of a similar quantity of ethyl alcohol.
Once the initial symptoms have passed, a second set of symptoms arises 10-30 hours after the initial exposure to methanol: blurring or complete loss of vision, together with acidosis. These symptoms result from the accumulation of toxic levels of formate in the bloodstream, and may progress to death by respiratory failure. The ester derivatives of methanol do not share this toxicity.
Ethanol is sometimes denatured (adulterated), and thus made undrinkable, by the addition of methanol. The result is known as methylated spirit or "meths" (UK use). (The latter should not be confused with meth, a common abbreviation for methamphetamine.)
See Also:
| Methane | Ethanol |
| Ethane | Methanol |
| Butane | Decane |
| Hexane | Octane |
| Propane | Pentane |