Ethanol

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The chemical compound ethanol, also known as ethyl alcohol or grain alcohol, is the bio-alcohol found in alcoholic beverages. When non-chemists refer to "alcohol", they almost always mean ethanol. It is also increasingly being used as a fuel (usually replacing or complementing gasoline). Ethanol's chemical formula is C₂H₅OH and its molecular structure is

H H

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    H-C-C-O-H

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H H

This article is mostly about ethanol as a chemical compound. For issues related to ethanol-containing beverages, see alcoholic beverages. For the use of fuel ethanol in transportation, see alcohol as a fuel.

Table of contents

1 Properties
2 Production
3 See also
4 External links

Properties

Pure ethanol is a flammable, colorless liquid with a boiling point of 78.5° C. Its low melting point of -114.5° C allows it to be used in antifreeze products. It has a pleasant odor reminiscent of whiskey.

Its density is 789 g/L, about 20% less than that of water. It is easily soluble in water and is itself a good solvent, used in perfumes, paints and tinctures. Alcoholic drinks have a large variety of tastes, since various flavor compounds are dissolved during brewing.

A solution of 70-85% of ethanol is commonly used as a disinfectant; it kills organisms by denaturing their proteins and dissolving their lipids: it is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores. This disinfectant property of ethanol is the reason that alcoholic beverages can be stored for a long time.

Ethanol can lose a proton from the hydroxyl group and is a very weak acid, weaker than water.

The CAS number of ethanol is 64-17-5 and its UN number is UN 1170.

Production

Ethanol for use in alcoholic beverages is produced by fermentation: it is a product of sugar metabolism in certain species of yeast in the absence of oxygen. The process of culturing yeast under conditions to produce alcohol is referred to as brewing. Yeasts can grow in the presence of up to only about 14% alcohol, but the concentration of alcohol in the final product can be increased by distillation.

Ethanol is also used as a fuel and in a wide variety of industrial processes. Ethanol for industrial use is often made from petroleum feedstocks, typically from ethylene; this is cheaper than the production by fermentation.

Ethanol for industrial use is normally denatured, meaning small amounts of unpleasant or toxic substances (such as methanol) are added so that it cannot be consumed by humans, thus avoiding the relevant taxes. Denatured ethanol has the UN number UN 1987 and toxic denatured ethanol has UN 1986.