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Ethyl alcohol
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Ethyl alcohol

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Properties
General
Name Ethanol

Chemical formula C2H5OH
Atomic weight 46.07 amu
CAS number 64-17-5
UN number 1170
Phase behavior
Melting point 158.8 K (-114.3°C;)
Boiling point 351.5 K (78.4°C)
Triple point 159 K (-114°C)
Critical point 514 K (241°C)
63 bar
ΔfusH; 4.9 kJ/mol
ΔfusS; 31 J/mol·K
ΔvapH; 38.56 kJ/mol
Solubility Soluble in water
Acid-base properties
pKa 15.9
Liquid properties
ΔfH0liquid; -277 kJ/mol
S0liquid 159.9 J/mol·K
Cp 112.4 J/mol·K
Density 789 gram/L
Gas properties
ΔfH0gas; -235.3 kJ/mol
S0gas ? J/mol·K
Cp 65.21 J/mol·K
Safety
Acute effects Nausea, vomiting, CNS depression. Respiratory failure in severe cases.
Chronic effects Dependency. Liver cirrhosis.
Flash point 17°C
Autoignition temperature 425°C
Explosive limits 3.5-15%
More information
Properties NIST WebBook
MSDS Hazardous Chemical Database
Unless otherwise stated, all data was produced under conditions of standard temperature and pressure.

Disclaimer and references

Ethyl alcohol, also known as ethanol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols, that is most often found in alcoholic beverages. In common parlance, it is often referred to simply as alcohol. Its chemical formula is CH3CH2OH.

This article is mostly about ethanol as a chemical compound. For beverages containing ethanol, see alcoholic beverages. For the use of ethanol as a fuel, see alcohol fuel.

Table of contents
1 History
2 Production
3 Use
4 See also
5 External links

History

Ethanol has been known to humans since prehistory as the active ingredient of alcoholic beverages. Its isolation as a relatively pure compound was probably achieved first by Islamic alchemists who developed the art of distillation, such as Geber (721-815) and Al-Razi (864-930).

The name alcohol comes from the Arabic language al-kul. alchemists used al-kul to refer to any of a number of fine powders produced by chemical process. Al-kul was also used for substances that were made by process of distillation, the earliest recorded English use for this meaning of the term is from 1672. "Alcohol of wine," was the term first used for fermented liquors that caused intoxication. Originally referred to the processed and distilled "essence," it later referred to the "essence" which caused the effect of intoxication, and later was used for the liquid, and in recently science contexts, for the chemical known today.

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.

For a mixture of ethanol and water, there is a maximum boiling azeotrope at 95% and 5% water. For this reason fractional distillation of ethanol-water mixtures (of less than 95% ethanol) cannot yield ethanol purer than 95%. Therefore, 95% ethanol in water is a fairly common solvent.

To produce absolute ethanol, a small amount of benzene is added, and the mixture is again fractionally distilled. Benzene forms a trinary azeotrope with water and ethanol to remove the last of the water, and a binary azeotrope with ethanol removes most of the benzene. The resulting ethanol is water free, for processes that require it. However, several ppm of benzene remains, so consumption by humans leads to distinctive liver damage.

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 made unfit for human consumption ("denatured") by the inclusion of small amounts of substances that are either toxic (such as methanol) or unpleasant (such as denatonium benzoate), thus avoiding the applicable taxes or inventory controls. Denatured ethanol has the UN number UN 1987 and toxic denatured ethanol has UN 1986.

Use

Ethanol is used in antifreeze products for its low melting point.

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 because 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 and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores. Because of this disinfectant property, alcoholic beverages can be stored for a long time.

See also

External links