Friday, May 18, 2007

Alcohol

Generally, the word alcohol, when used alone, usually refers to ethanol, also known as grain alcohol or (older) spirits of wine. Ethanol is a very strong and unique smelling, colorless, volatile
liquid formed by the fermentation of sugars. It also often refers to any beverage that contains ethanol . It is the most widely used depressant in the world, and has been for thousands of years. This sense underlies the term alcoholism (addiction to alcohol).

Sources:

Many alcohols can be created by fermentation of fruits or grains with yeast, but only ethanol is commercially produced this way — chiefly for fuel and drink. Other alcohols are generally produced by synthetic routes from natural gas, petroleum, or coal feed stocks; for example,
via acid catalyzed hydration of alkenes. For more details see Preparation of alcohols.

Uses:
Automotive:


Alcohol is often used as an automotive fuel. Ethanol and methanol can be made to burn more cleanly than gasoline or diesel. Alcohol was once commonly used as an antifreeze in automobile radiators. To add to an internal combustion engine's performance, Methanol may be injected into turbocharged and supercharged engines. This cools the air intake charge, providing a denser air charge.

Scientific, medical, and industrial:

Alcohols are in wide use in industry and science as reagents or solvents. Because of its low toxicity and ability to dissolve non-polar substances, ethanol is often used as a solvent in medical drugs, perfumes, and vegetable essences such as vanilla. In organic synthesis, alcohols frequently serve as versatile intermediates.Ethanol is often used as an antiseptic, to disinfect the skin before injections are given, often along with iodine. Ethanol-based soaps are now becoming commonplace within restaurants and are particularly convenient as they do not require drying due to the volatility of the compound. Alcohol is also used as a preservative for specimens.

Toxicity:

Alcohols often have an odor described as 'biting' that 'hangs' in the nasal passages. Ethanol in the form of alcoholic beverages has been consumed by humans since pre-historic times, for a variety of hygienic, dietary, medicinal, religious, and recreational reasons. While infrequent consumption of ethanol in small quantities may be harmless or even beneficial, larger doses result in a state known as drunkenness or intoxication (which may lead to a hangover as the effect wears off)
and, depending on the dose and regularity of use, can cause acute respiratory failure or death and with chronic use has medical repercussions. Because alcohol impairs judgment, it can often be a catalyst for reckless or irresponsible behavior. The LD50 of ethanol in rats is 11,300 mg/kg. This ratio would correspond to an 80kg (176.4lb) man drinking 65 shots of 80 proof alcohol, although the LD50 does not necessarily translate directly to humans. A more accurate but less precise figure would estimate the LD50 of the same 80kg (176.4lb) at about 15.5 shots of 80 proof alcohol.Other alcohols are substantially more poisonous than ethanol, partly
because they take much longer to be metabolized, and often their metabolism produces even more toxic substances. Methanol, or wood alcohol, for instance, is oxidized by alcohol ehydrogenase enzymes in the liver to the poisonous formaldehyde, which can cause blindness or
death.

An effective treatment to prevent formaldehyde toxicity after methanol ingestion is to dminister ethanol. Alcohol dehydrogenase has a higher affinity for ethanol, thus preventing methanol from binding and acting as a substrate. Any remaining methanol will then have time to be excreted through the kidneys. Remaining formaldehyde will be converted to formic acid and excreted.