Ethanol
| General | |
|---|---|
| Name | Ethanol |
 | |
| Chemical formula | C2H5OH |
| Formula weight | 46.07 amu |
| Synonyms | Ethyl Alcohol, Grain Alcohol |
| 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) |
| Thermal decomposition | ? K (?°C) |
| Triple point | 150 K (-123.1°C)
|
| Critical point | 514 K (240.9°C)
|
| ΔfusH | 4.9 kJ/mol |
| ΔfusS | 31 J/mol·K |
| ΔvapH | 38.56 kJ/mol |
| Solubility | Miscible with 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 | 0.789 ×103 kg/m3 |
| 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 info | |
| Properties | NIST WebBook |
| MSDS | Hazardous Chemical Database |
| SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
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. Its chemical formula is CH3CH2OH.
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 (replacing or complementing gasoline), see alcohol as a fuel.
| Table of contents |
|
2 History 3 Production 4 See also 5 External links |
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. Its odor is reminiscent of vodka.
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 is a very weak acid, weaker than water, and can lose a proton from the hydroxyl group forming the ethanoate ion C2H5O-.
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.
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.
Properties
History
Production
See also
External links