View source for Ethanol

{{for|beverages containing ethanol|alcoholic beverage}}
{{for|the use of ethanol as a fuel|alcohol fuel}}
{{Chembox new
| ImageFile = Ethanol-2D-skeletal.svg
| ImageFile1 = Ethanol-3D-vdW.png
| IUPACName = Ethanol
| OtherNames = Ethyl alcohol; grain alcohol; hydroxyethane; drinking alcohol
| Section1 = {{Chembox Identifiers
| SMILES = CCO
| CASNo = 64-17-5
| RTECS = KQ6300000
 }}
| Section2 = {{Chembox Properties
| Formula = C<sub>2</sub>H<sub>5</sub>OH
| MolarMass = 46.06844(232) g/mol
| Appearance = colorless clear liquid
| Density = 0.789 g/cm³, liquid
| Solubility = Fully [[miscible]]
| MeltingPt = −114.3&nbsp;°C (158.8 K)
| BoilingPt = 78.4&nbsp;°C (351.6 K)
| pKa = 15.9 (H<sup>+</sup> from OH group)
| Viscosity = 1.200 mPa·s ([[Poise|cP]]) at 20.0&nbsp;°C
| Dipole = 5.64 fC·fm (1.69 [[Debye|D]]) (gas)
 }}
| Section7 = {{Chembox Hazards
| FlashPt = 286.15 K (13&nbsp;°C or 55.4&nbsp;°F)
| EUClass = Flammable ('''F''')
| NFPA-F = 3
| RPhrases = {{R11}}
| SPhrases = {{S2}}, {{S7}}, {{S16}}
 }}
| Section8 = {{Chembox Related
| Function = [[alcohol]]s }}
}}





==Overview==
'''Ethanol''', also known as '''ethyl alcohol''', '''drinking alcohol''' or '''grain alcohol''', is a flammable, colorless, slightly toxic [[chemical compound]], and is best known as the [[alcohol]] found in [[alcoholic beverage]]s. In common usage, it is often referred to simply as ''alcohol''. Its [[chemical formula|molecular formula]] is variously represented as EtOH, CH<sub>3</sub>CH<sub>2</sub>OH, C<sub>2</sub>H<sub>5</sub>OH or as its [[empirical formula]] [[Carbon|C]]<sub>2</sub>[[Hydrogen|H]]<sub>6</sub>[[Oxygen|O]] (which it shares with [[dimethyl ether]]).

After the use of fire, fermentation of sugar into ethanol is perhaps the earliest [[organic reaction]] known to humanity, and the intoxicating effects of ethanol consumption have certainly been known since ancient times. In modern times ethanol intended for industrial use has also been produced from byproducts of petroleum refining.

Because of ethanol's ease of production and its low toxicity, it finds widespread use as a solvent for substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry it is both an essential solvent and a fundamental feedstock for the synthesis of other products. Because it burns cleanly, ethanol has a long history as a fuel, including as a fuel for [[internal combustion engine]]s.

== History ==
Ethanol has been used by humans since prehistory as the intoxicating ingredient in [[alcoholic beverage]]s. Dried residues on 9000-year-old pottery found in northern [[mainland China]] imply the use of alcoholic beverages even among [[Neolithic]] peoples.<ref name="Roach">{{cite journal|author=Roach, J.|date=July 18, 2005|url=http://news.nationalgeographic.com/news/2005/07/0718_050718_ancientbeer.html|title= 9,000-Year-Old Beer Re-Created From Chinese Recipe.|journal=National Geographic News|accessdate= 2007-09-03}}</ref> Its isolation as a relatively pure compound was first achieved by [[Persian people|Persian]] alchemists who developed the art of [[distillation]] during the [[Abbasid caliphate]], the most notable of whom was [[Al-Razi]]. The writings attributed to [[Jabir Ibn Hayyan]] (Geber) (721-815) mention the flammable vapors of boiled wine. [[Al-Kindī]] (801-873) unambiguously described the distillation of wine.<ref name="al-Hassan">{{cite web|author=[[Ahmad Y Hassan]]|url=http://www.gabarin.com/ayh/Notes/Notes%207.htm|title=Alcohol and the Distillation of Wine in Arabic Sources.|accessdate=2007-09-03|publisher=www.history-science-technology.com}}</ref> Absolute ethanol was first obtained in 1796 by Johann Tobias Lowitz, by filtering distilled ethanol through [[Activated carbon|charcoal]].

[[Antoine Lavoisier]] described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808, [[Nicolas-Théodore de Saussure]] determined ethanol's chemical formula. Fifty years later [[Archibald Scott Couper]] published a structural formula for ethanol, which places ethanol among the first of chemical compounds to have its chemical structures determined.<ref name="Couper">{{cite journal|author=Couper, A.S.|year=1858|title=On a new chemical theory|journal=Philosophical magazine (online reprint)|volume=16|issue=104&ndash;116|url=http://web.lemoyne.edu/~giunta/couper/couper.html|accessdate=2007-09-03}}</ref>

Ethanol was first prepared synthetically in 1826, through the independent efforts of Henry Hennel in Great Britain and S.G. Sérullas in [[France]]. [[Michael Faraday]] prepared ethanol by the [[Acid catalysis|acid-catalyzed]] hydration of [[ethylene]] in 1828, in a process similar to that used for industrial ethanol synthesis today.<ref name="Hennell">{{cite journal|author=Hennell, H. |year=1828|title=On the mutual action of sulfuric acid and alcohol, and on the nature of the process by which ether is formed.|journal=Philosophical Transactions|volume=118|issue=365&ndash;371}}</ref>

Ethanol served as lamp fuel in the United States as early as 1840, although taxes levied during the [[Civil War]] on industrial alcohol rendered the practice uneconomical.<ref name="siegel">{{cite news|url=http://www.npr.org/templates/story/story.php?storyId=7426827|title=Ethanol, Once Bypassed, Now Surging Ahead|author=Robert Siegel|publisher=NPR|date=February 15, 2007|accessdate=2007-09-22}}</ref> The tax was not repealed until 1906,<ref name="siegel"/> and by 1908 ethanol was used to power early Model T automobiles.<ref name="dipardo">{{cite web|url=http://tonto.eia.doe.gov/FTPROOT/features/biomass.pdf|title=Outlook for Biomass Ethanol Production and Demand|publisher=United States Department of Energy|author=Joseph DiPardo|accessdate=2007-09-22}}</ref> With the advent of [[Prohibition]] in 1920 though, sellers of ethanol fuel were accused of being allies of moonshiners,<ref name="siegel"/> and ethanol fuel once again faded from the public eye. The recent rise in oil prices has spurred renewed interest.

==Physical properties==
[[Image:Ethanol-3d-stick-structure.svg|thumb|left|150px|Chemical structure of ethanol]]

The properties of ethanol stem primarily from the presence of its hydroxyl group and the shortness of its carbon chain. Ethanol's hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight. Ethanol, like most short-chain alcohols, is flammable, colorless, has a strong odor, and is volatile.

Ethanol is slightly more refractive than water with a [[refractive index]] of 1.36242 (at ''&lambda;''=589.3&nbsp;nm and 18.35&nbsp;°C).<ref name="crc"/>

Ethanol is a versatile solvent, [[miscible]] in all proportions with water and many organic solvents, including [[acetic acid]], [[acetone]], [[benzene]], [[carbon tetrachloride]], [[chloroform]], [[diethyl ether]], [[ethylene glycol]], [[glycerol]], [[nitromethane]], [[pyridine]], and [[toluene]].<ref name="crc"/><ref name="merck"/> It is also miscible with light aliphatic hydrocarbons such as [[pentane]] and [[hexane]], as well as aliphatic chlorides such as [[1,1,1-Trichloroethane|trichloroethane]] and [[tetrachloroethylene]].<ref name="merck">''Merck Index of Chemicals and Drugs'', 9th ed.</ref> Ethanol's miscibility with water is in contrast to longer chain alcohols (five or more carbons), whose water solubility decreases rapidly as the number of carbons increases.<ref name="m_and_b"/>

Hydrogen bonding causes pure ethanol to be [[hygroscopic]] to the extent that it readily absorbs water from the air. The polar nature of the hydroxyl group causes ethanol to dissolve many ionic compounds, notably [[sodium hydroxide|sodium]] and [[potassium hydroxide]]s, [[magnesium chloride]], [[calcium chloride]], [[ammonium chloride]], [[ammonium bromide]], and [[sodium bromide]].<ref name="merck"/> [[Sodium chloride|Sodium]] and [[potassium chloride]]s are slightly soluble in ethanol.<ref name="merck"/> Because the ethanol molecule also has a nonpolar end, it also dissolves nonpolar substances, including most [[essential oil]]s,<ref name="merckoils">''Merck Index of Chemicals and Drugs'', 9th ed.; monographs 6575 through 6669</ref> as well as numerous flavoring, coloring, and medicinal agents.

Several unusual phenomena are associated with mixtures of ethanol and water. Ethanol-water mixtures have less volume than their individual components. A mixture of equal volumes ethanol and water has only 95.6% of the volume of equal parts ethanol and water, unmixed (at 15.56&nbsp;°C).<ref name="crc">''CRC Handbook of Chemistry'', 44th ed.</ref> The addition of even a few percent of ethanol to water sharply reduces the [[surface tension]] of water. This property partially explains the [[tears of wine]] phenomenon. When wine is swirled in a glass, ethanol evaporates quickly from the thin film of wine on the wall of the glass. As its ethanol content decreases, its surface tension increases, and the thin film beads up and runs down the glass in channels rather than as a smooth sheet.

Ethanol and mixtures with water greater than about 50% ethanol are [[flammable]] and easily ignited. Ethanol-water solutions below 50% ethanol by volume may also be flammable if the solution is vaporized by heating (as in some cooking methods that call for [[wine]] to be added to a hot pan, causing it to flash boil into a vapor, which is then ignited to "burn off" excessive alcohol).

==Chemistry==
{{Details|Alcohol}}
Ethanol is classified as a primary alcohol, meaning that the carbon to which its hydroxyl group is attached has at least two hydrogen atoms attached to it as well.

The chemistry of ethanol is largely that of its [[hydroxyl]] group.

; Acid-base chemistry

Ethanol's hydroxyl proton is very weakly acidic; it is an even weaker acid than water. Ethanol can be quantitatively converted to its [[conjugate base]], the [[Alkoxide|ethoxide]] ion (CH<sub>3</sub>CH<sub>2</sub>O<sup>−</sup>), by reaction with an [[alkali metal]] such as [[sodium]]:<ref name="m_and_b"/>

: 2CH<sub>3</sub>CH<sub>2</sub>OH + 2[[sodium|Na]] → 2CH<sub>3</sub>CH<sub>2</sub>ONa + [[hydrogen|H<sub>2</sub>]]

; Halogenation

Under special conditions, ethanol reacts with [[hydrogen halide]]s to produce [[Haloalkane|ethyl halides]] such as [[ethyl chloride]] and [[ethyl bromide]]:

: CH<sub>3</sub>CH<sub>2</sub>OH + [[hydrochloric acid|HCl]] → [[ethyl chloride|CH<sub>3</sub>CH<sub>2</sub>Cl]] + [[water|H<sub>2</sub>O]]

HCl reaction requires a catalyst such as [[zinc chloride]].<ref name="s_and_h">{{cite book|author=Streitweiser, Andrew Jr.; Heathcock, Clayton H.|title=Introduction to Organic Chemistry|date=1976|publisher=MacMillan|isbn=0-02-418010-6}}</ref>

: CH<sub>3</sub>CH<sub>2</sub>OH + [[Hydrobromic acid|HBr]] → [[Ethyl bromide|CH<sub>3</sub>CH<sub>2</sub>Br]] + [[water|H<sub>2</sub>O]]

HBr requires [[refluxing]] with a [[sulfuric acid]] catalyst.<ref name="s_and_h"/>

Ethyl halides can also be produced by reacting ethanol with more specialized [[Halogenation|halogenating agents]], such as [[thionyl chloride]] for preparing ethyl chloride, or [[phosphorus tribromide]] for preparing ethyl bromide.<ref name="m_and_b"/><ref name="s_and_h"/>

; Ester formation

Under acid-catalyzed conditions, ethanol reacts with [[carboxylic acid]]s to produce ethyl [[ester]]s and water:

: [[carboxylic acid|RCOOH]] + HOCH<sub>2</sub>CH<sub>3</sub> → [[ester|RCOOCH<sub>2</sub>CH<sub>3</sub>]] + [[water|H<sub>2</sub>O]]

For this reaction to produce useful yields it is necessary to remove water from the reaction mixture as it is formed.

Ethanol can also form esters with inorganic acids. [[Diethyl sulfate]] and [[triethyl phosphate]], prepared by reacting ethanol with [[sulfuric acid|sulfuric]] and [[phosphoric acid]] respectively, are both useful ethylating agents in [[organic synthesis]]. [[Ethyl nitrite]], prepared from the reaction of ethanol with [[sodium nitrite]] and [[sulfuric acid]], was formerly a widely-used [[diuretic]].

; Dehydration

Strong acid desiccants, such as sulfuric acid, cause ethanol's dehydration to form either [[diethyl ether]] or [[ethylene]]:

: 2 CH<sub>3</sub>CH<sub>2</sub>OH → [[diethyl ether|CH<sub>3</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>3</sub>]] + [[water|H<sub>2</sub>O]]

: CH<sub>3</sub>CH<sub>2</sub>OH → [[ethylene|H<sub>2</sub>C=CH<sub>2</sub>]] + [[water|H<sub>2</sub>O]]

Which product, diethyl ether or ethylene, predominates depends on the precise reaction conditions.

; Oxidation
[[image:Chemistry, Combustion of Ethanol 002.jpg|thumb|right|Ethanol combusting in an evaporating dish]]
Ethanol can be oxidized to [[acetaldehyde]], and further oxidized to [[acetic acid]]. In the human body, these oxidation reactions are catalyzed by [[enzyme]]s. In the laboratory, aqueous solutions of strong oxidizing agents, such as [[chromic acid]] or [[potassium permanganate]], oxidize ethanol to acetic acid, and it is difficult to stop the reaction at acetaldehyde at high yield. Ethanol can be oxidized to acetaldehyde, without over oxidation to acetic acid, by reacting it with [[pyridinium chromic chloride]].<ref name="s_and_h"/>

; Chlorination
When exposed to [[chlorine]], ethanol is both oxidized and its [[alpha carbon]] chlorinated to form the compound, [[chloral]].

: 4Cl<sub>2</sub> + C<sub>2</sub>H<sub>5</sub>OH → C<sub>2</sub>HCl<sub>3</sub>O + 5HCl

; Combustion

[[Combustion]] of ethanol forms [[carbon dioxide]] and [[water]]:

:C<sub>2</sub>H<sub>5</sub>OH + 3 O<sub>2</sub> → 2 CO<sub>2</sub> + 3 H<sub>2</sub>O

== Production ==
[[Image:Ethanol Flasche.jpg|thumb|left|94% denatured ethanol sold in a bottle for household use.]]

Ethanol is produced both as a [[petrochemical]], through the hydration of [[ethylene]], and biologically, by [[fermentation (biochemistry)|fermenting]] sugars with [[yeast]].<ref name="Mills-Ecklund">Mills, G.A.; Ecklund, E.E. "[http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.eg.12.110187.000403?journalCode=energy Alcohols as Components of Transportation Fuels]." ''Annual Review of Energy.'' November 1987. Vol. 12, 47-80. Retrieved on [[September 2]], [[2007]].</ref> Which process is more economical is dependent upon the prevailing prices of petroleum and of grain feed stocks.

=== Ethylene hydration ===
Ethanol for use as industrial feedstock is most often made from [[petrochemical]] feed stocks, typically by the [[acid]]-[[catalysis|catalyzed]] hydration of [[ethylene]], represented by the [[chemical equation]]

: [[ethylene|C<sub>2</sub>H<sub>4</sub>]]<sub>(g)</sub> + [[water|H<sub>2</sub>O]]<sub>(g)</sub> → CH<sub>3</sub>CH<sub>2</sub>OH<sub>(l)</sub>

The catalyst is most commonly [[phosphoric acid]],<ref name="r_and_c">{{cite book|author=Roberts, John D.; Caserio, Marjorie C.|date=1977|publisher=W. A. Benjamin, Inc|title=Basic Principles of Organic Chemistry|isbn=0-8053-8329-8}}</ref> [[adsorption|adsorbed]] onto a porous support such as [[diatomaceous earth]] or [[charcoal]]. This catalyst was first used for large-scale ethanol production by the [[Shell Oil Company]] in 1947.<ref name="ECT4 820">Lodgsdon, J.E. (1994). "Ethanol." In J.I. Kroschwitz (Ed.) ''Encyclopedia of Chemical Technology, 4th ed.'' vol. 9, p. 820. New York: John Wiley & Sons.</ref> The reaction is carried out at with an excess of high pressure steam at 300&nbsp;°C.

In an older process, first practiced on the industrial scale in 1930 by [[Union Carbide]],<ref name="ECT4 817">Lodgsdon, J.E. (1994). p. 817</ref> but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated [[sulfuric acid]] to produce [[ethyl sulfate]], which was then [[hydrolysis|hydrolyzed]] to yield ethanol and regenerate the sulfuric acid:<ref name="s_and_h"/>

: [[ethylene|C<sub>2</sub>H<sub>4</sub>]] + [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] → [[ethyl sulfate|CH<sub>3</sub>CH<sub>2</sub>SO<sub>4</sub>H]]

: [[ethyl sulfate|CH<sub>3</sub>CH<sub>2</sub>SO<sub>4</sub>H]] + [[water|H<sub>2</sub>O]] → CH<sub>3</sub>CH<sub>2</sub>OH + [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]]

=== Fermentation ===
{{details|Ethanol fermentation}}

Ethanol for use in [[alcoholic beverage]]s, and the vast majority of ethanol for use as fuel, is produced by fermentation. When certain species of [[yeast]], most importantly, ''[[Saccharomyces cerevisiae]]'', [[metabolism|metabolize]] [[polysaccharide|sugar]] in the absence of [[oxygen]], they produce ethanol and [[carbon dioxide]]. The chemical equation below summarizes the conversion:

: [[glucose|C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>]] → 2 CH<sub>3</sub>CH<sub>2</sub>OH + 2 [[carbon dioxide|CO<sub>2</sub>]]

The process of culturing yeast under conditions to produce alcohol is called as [[brewing]]. Ethanol's toxicity to yeast limits the ethanol concentration obtainable by brewing. The most ethanol-tolerant strains of yeast can survive up to approximately 15% ethanol by volume.<ref name="mosttolerant">Morais, P.B.; Rosa, C.A.; Linardi, V.R.; Carazza, F.; Nonato, E.A. "[http://www.springerlink.com/content/h32k825756g41318/ Production of fuel alcohol by Saccharomyces strains from tropical habitats]." ''Biotechnology Letters.'' November 1996. Vol. 18, No. 11, 1351-1356. Retrieved on [[September 2]], [[2007]].</ref>

The fermentation process must exclude oxygen. If oxygen is present, yeast undergo [[aerobic respiration]] which produces [[carbon dioxide]] and water rather than ethanol.

In order to produce ethanol from starchy materials such as [[cereal grain]]s, the starch must first be converted into sugars. In brewing [[beer]], this has traditionally been accomplished by allowing the grain to germinate, or [[malt]], which produces the [[enzyme]], [[amylase]]. When the malted grain is [[mashing|mashed]], the amylase converts the remaining starches into sugars. For fuel ethanol, the hydrolysis of starch into glucose can be accomplished more rapidly by treatment with dilute sulfuric acid, [[fungi|fungally]] produced amylase, or some combination of the two.<ref name="hydrolysis">Badger, P.C. "[http://www.hort.purdue.edu/newcrop/ncnu02/v5-017.html Ethanol From Cellulose: A General Review]." p. 17–21. In: J. Janick and A. Whipkey (eds.), Trends in new crops and new uses. ASHS Press, 2002, Alexandria, VA. Retrieved on [[September 2]], [[2007]].</ref>

===Cellulosic ethanol===
{{main|Cellulosic ethanol}}

Sugars for [[ethanol fermentation]] can be obtained from [[cellulose]]. Until recently, however, the cost of the [[cellulase]] enzymes capable of hydrolyzing cellulose has been prohibitive. The [[Canada|Canadian]] firm, [[Iogen]], brought the first cellulose-based ethanol plant on-stream in 2004.<ref name="Ritter">Ritter, S.K. ([[May 31]] [[2004]]). "Biomass or Bust." ''Chemical & Engineering News'' '''82'''(22), 31–34.</ref> Its primary consumer so far has been the Canadian government, which, along with the [[United States Department of Energy]], has invested heavily in the commercialization of cellulosic ethanol. Deployment of this technology could turn a number of cellulose-containing agricultural byproducts, such as [[corncob]]s, [[straw]], and [[sawdust]], into renewable energy resources. Other enzyme companies are developing genetically engineered fungi that produce large volumes of cellulase, xylanase and hemicellulase enzymes. These would convert agricultural residues such as corn stover, wheat straw and sugar cane bagasse and energy crops such as [[switchgrass]] into fermentable sugars.<ref>{{cite web | author = Clines, Tom | title = Brew Better Ethanol | publisher = Popular Science Online | date = July 2006 | url = http://www.popsci.com/popsci/energy/6756226d360ab010vgnvcm1000004eecbccdrcrd.html}}</ref>

Cellulose-bearing materials typically also contain other [[polysaccharide]]s, including [[hemicellulose]]. When [[hydrolysis|hydrolyzed]], hemicellulose decomposes into mostly five-carbon sugars such as [[xylose]]. ''S. cerevisiae'', the yeast most commonly used for ethanol production, cannot metabolize xylose. Other yeasts and bacteria are under investigation to ferment xylose and other [[pentose]]s into ethanol.<!--<ref>{{cite web|url=http://www.lub.lu.se/cgi-bin/show_diss.pl?db=global&fname=tec_748.html|title=www.lub.lu.se/cgi-bin/show_diss.pl?db=global&fname=tec_748.html}}</ref> --><ref>{{cite web|url=http://www.metabolicengineering.gov/me2001/2001Kompala.pdf|title=Maximizing Ethanol Production by Engineered Pentose-Fermenting ''Zymononas mobilis''|author=Dhinakar S. Kompala|publisher=Department of Chemical Engineering, University of Colorado at Boulder|accessdaymonth=21 May|accessyear=2007}}</ref>

=== Prospective technologies ===
The [[anaerobic bacteria|anaerobic bacterium]] ''[[Clostridium]] ljungdahlii'', recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including [[synthesis gas]], a mixture of [[carbon monoxide]] and [[hydrogen]] that can be generated from the partial [[combustion]] of either [[fossil fuel]]s or [[biomass]]. Use of these bacteria to produce ethanol from synthesis gas has progressed to the pilot plant stage at the BRI Energy facility in [[Fayetteville, Arkansas]].<ref>{{cite web|url=http://www.brienergy.com/|title=Providing for a Sustainable Energy Future|publisher=Bioengineering Resources, inc|accessdaymonth=21 May|accessyear=2007}}</ref>

Another prospective technology is the closed-loop ethanol plant.<ref name="clAlc">{{cite journal|url=http://www.renewableenergyaccess.com/rea/news/story?id=46414|title= Closed-Loop Ethanol Plant to Start Production|date=November 2, 2006|publisher=www.renewableenergyaccess.com|accessdate=2007-09-03}}</ref> Ethanol produced from corn has a number of critics who suggest that it is primarily just recycled fossil fuels because of the energy required to grow the grain and convert it into ethanol. However, the closed-loop ethanol plant attempts to address this criticism. In a closed-loop plant, the energy for the distillation comes from fermented manure, produced from cattle that have been fed the by-products from the distillation. The leftover manure is then used to fertilize the soil used to grow the grain. Such a process is expected to have a much lower fossil fuel requirement.<ref name="Rapier-1">Rapier, R. ([[June 26]] [[2006]]) [http://i-r-squared.blogspot.com/2006/06/e3-biofuels-responsible-ethanol.html "E3 Biofuels: Responsible Ethanol"] R-Squared Energy Blog</ref>

Though in an early stage of research, there is some development of alternative production methods that use feed stocks such as municipal waste or recycled products, rice hulls, sugarcane bagasse, small diameter trees, wood chips, and switchgrass.<ref>{{cite web|url=http://www.truthout.org/issues_06/041607ED.shtml|title=Air Pollution Rules Relaxed for US Ethanol Producers|publisher=Truthout|date=12 April 2007|accessdaymonth=21 May|accessyear=2007}}</ref>

===Testing===
[[Image:Ethanol near IR spectrum.png|thumb|right|240px|[[Near infrared spectrum]] of liquid ethanol.]]
Breweries and biofuel plants employ two methods for measuring ethanol concentration. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the CH band at 2900&nbsp;cm<sup>−1</sup>. This method uses a relatively inexpensive solid state sensor that compares the CH band with a reference band to calculate the ethanol content. The calculation makes use of the [[Beer-Lambert law]]. Alternatively, by measuring the density of the starting material and the density of the product, using a [[hydrometer]], the change in specific gravity during fermentation indicates the alcohol content. This inexpensive and indirect method has a long history in the beer brewing industry.

=== Purification ===
{{main|Ethanol purification}}

Ethylene hydration or brewing produces an ethanol-water mixture. For most industrial and fuel uses, the ethanol must be purified. [[Fractional distillation]] can concentrate ethanol to 95.6% by weight (89.5 mole%). This mixture is an [[azeotrope]] with a boiling point of 78.1&nbsp;°C, and cannot be further purified by distillation.

In one common industrial method to obtain absolute alcohol, a small quantity of [[benzene]] is added to [[rectified spirit]] and the mixture is then distilled. Absolute alcohol is obtained in the third fraction, which distills over at 78.3 [[degree Celsius|°C]] (351.4 [[kelvin|K]]).<ref name="m_and_b">{{cite book|author=Morrison, Robert Thornton; Boyd, Robert Neilson|title=Organic Chemistry, 2nd ed.|year=1972|publisher=Allyn and Bacon, inc.}}</ref> Because a small amount of the benzene used remains in the solution, absolute alcohol produced by this method is not suitable for consumption, as benzene is [[carcinogenic]].<ref>{{cite journal |author=Snyder R, Kalf GF |title=A perspective on benzene leukemogenesis |journal=Crit. Rev. Toxicol. |volume=24 |issue=3 |pages=177–209 |year=1994 |pmid=7945890}}</ref>

There is also an absolute alcohol production process by [[desiccation]] using [[glycerol]]. Alcohol produced by this method is known as spectroscopic alcohol — so called because the absence of benzene makes it suitable as a solvent in [[spectroscopy]].

Other methods for obtaining absolute ethanol include desiccation using adsorbents such as starch or [[zeolite]]s, which adsorb water preferentially, as well as [[azeotropic distillation]] and [[extractive distillation]].<br clear="all">

==Types of ethanol==
=== Alcoholic beverages ===
Distilled [[alcoholic beverages]] are usually distilled to a high purity and then diluted. However, in some countries such as [[Poland]], [[rectified spirit]] (95-96%) is sold directly to the consumer, for human consumption.<ref>{{cite web|url=http://www.stawskidistributing.com/polishspirits.html |title=Poland: Stawski Spirit |publisher=Stawski Imports |accessdate=2007-10-08}}</ref> Also, [[vodka]] is rectified spirit diluted to 37.5-60% [[alcohol by volume]].

=== Denatured alcohol ===
{{Main|Denatured alcohol}}

Pure ethanol and alcoholic beverages are heavily taxed. Ethanol has many applications that do not involve human consumption. To relieve the tax burden on these application, most jurisdictions waive the tax when agents have been added to the ethanol to render it unfit for human consumption. These include bittering agents such as [[denatonium benzoate]], as well as toxins such as [[methanol]], [[naphtha]], and [[pyridine]].<ref>{{cite web|url=http://www.procurement.umich.edu/Contracts/Denatured_Alchohol.pdf|title=U-M Program to Reduce the Consumption of Tax-free Alcohol; Denatured Alcohol a Safer, Less Expensive Alternative|publisher=University of Michigan|accessdate=2007-09-29}}</ref><ref>Great Britain (2005). ''[http://www.opsi.gov.uk/si/si2005/20051524.htm The Denatured Alcohol Regulations 2005].'' Statutory Instrument 2005 No. 1524. </ref>

===Absolute ethanol===
Absolute or anhydrous alcohol generally refers to purified ethanol, containing no more than one percent [[water]]. Absolute alcohol not intended for human consumption often contains trace amounts of toxic benzene.

Pure ethanol is classed as 200 [[Proof (alcohol)|proof]] in the USA, equivalent to 175 degrees proof in the (now rarely used) UK system.

===Neutralized ethanol===
Ethanol for analytic purposes is said to be neutralized when [[potassium hydroxide|potassium]] or [[sodium hydroxide]] is added to ethanol containing a [[pH]] indicator, such [[phenolphthalein]], until its color begins to turn. The solution can then be used in a titration to determine the pH of a test solution.

== Use ==
=== As a fuel===
{| class="wikitable" align="right"
! align = "left"|Fuel type
! align ="right"|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MJ/l
! align ="right"|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MJ/kg
! align ="right"|[[octane rating|Research<br>octane<br>number]]
|-
|[[ethanol fuel|Ethanol]]
| align ="right"|23.5
| align ="right"|31.1<ref>Calculated from heats of formation. Does not correspond exactly to the figure for MJ/l divided by density.</ref>
| align ="right"|129
|-
| [[Methanol]]
| align ="right"|17.9
| align ="right"|19.9
| align ="right"|123
|-
| Regular Gasoline
| align ="right"|34.8
| align ="right"|44.4<ref>[http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/storage.pdf|Thomas, George. Overview of Storage Development DOE Hydrogen Program [pdf]. Livermore, CA. Sandia National Laboratories. 2000.]</ref>
| align ="right"|Min 91
|-
| Premium Gasoline
| align ="right"|
| align ="right"|
| align ="right"|Min 95
|-
| [[Aviation gasoline]]<br>(high octane gasoline, not Jet fuel)
| align ="right"|33.5
| align ="right"|46.8
| align ="right"|
|-
| [[Alcohol fuel|Gasohol]]<br>(10% ethanol + 90% gasoline)
| align ="right"|33.7
| align ="right"|
| align ="right"|93/94
|-
| [[Autogas]] ([[Liquified petroleum gas|LPG]])<br>(60% [[Propane]] + 40% [[Butane]])
| align ="right"|26.8
| align ="right"|
| align ="right"|
|-
| [[Liquefied natural gas]]
| align ="right"|25.3
| align ="right"|~55
| align ="right"|
|-
| [[Diesel]]
| align ="right"|38.60
| align ="right"|45.41
| align ="right"|25
|-
!colspan="4"|Volumetric [[energy density]] of some fuels compared with ethanol:<ref name=TEDB>[http://www-cta.ornl.gov/data/Appendix_B.html Appendix B, Transportation Energy Data Book] from the [[Center for Transportation Analysis]] of the [[Oak Ridge National Laboratory]]</ref><br>
|}
{{main|Ethanol fuel}}

The largest single use of ethanol is as a motor [[fuel]] and fuel additive. The largest national fuel ethanol industries exist in [[Brazil]] (gasoline sold in Brazil contains at least 20% ethanol and hydrous ethanol is also used as fuel).<ref name="WaPo-Brazil">Reel, M. ([[August 19]] [[2006]]) [http://www.washingtonpost.com/wp-dyn/content/article/2006/08/19/AR2006081900842.html "Brazil's Road to Energy Independence"] The Washington Post.</ref>

Today, almost half of Brazilian cars are able to use 100% ethanol as fuel, which includes ethanol-only engines and flexible-fuel engines. Flex-fuel engines are able to work with all ethanol, all gasoline, or any mixture of both. Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown [[sugar cane]]. [[Sugar cane]] not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The [[bagasse]] generated by the process is not wasted, but is utilized in power plants as a surprisingly efficient fuel to produce electricity.

World production of ethanol in 2006 was 51 billion liters, (13.5 billion gallons), with 69% of the world supply coming from Brazil and the United States.<ref>{{cite web|url=http://www.ethanolrfa.org/industry/statistics/#E|title=Renewable Fuels Association Industry Statistics}}</ref>

The United States fuel ethanol industry is based largely on [[maize]]. According to the Renewable Fuels Association, as of November 2006, 107 grain ethanol biorefineries in the United States have the capacity to produce 5.1 billion gallons of ethanol per year. An additional 56 construction projects underway (in the U.S.) can add 3.8 billion gallons of new capacity in the next 18 months. Over time, it is believed that a material portion of the ~150 billion gallon per year market for gasoline will begin to be replaced with fuel ethanol.<ref name="rfa1">{{cite web|url=http://www.ethanolrfa.org/media/press/rfa/view.php?id=909|title=First Commercial U.S. Cellulosic Ethanol Biorefinery Announced|date=November 20, 2006|publisher=Renewable Fuels Association|accessdaymonth=21 May|accessyear=2006}}</ref>

The [[Energy Policy Act of 2005]] requires that 4 billion gallons of "renewable fuel" be used in 2006 and this requirement will grow to a yearly production of 7.5 billion gallons by 2012.<ref name="epa1">{{cite web|url=http://www.epa.gov/otaq/renewablefuels/|title= Renewable Fuel Standard Program|publisher=United States Environmental Protection Agency|date=April 10, 2007|accessdaymonth=21 May|accessyear=2007}}</ref>

[[Image:Ethanol Car.jpg|thumb|225px|right|A [[Ford Taurus]] "fueled by clean burning ethanol" owned by [[New York City]].]]
In the United States, ethanol is most commonly blended with gasoline as a 10% ethanol blend nicknamed "gasohol". This blend is widely sold throughout the U.S. [[Midwest]], and in cities required by the [[1990 Clean Air Act]] to oxygenate their gasoline during the winter.

==== Controversy ====
As reported in "The Energy Balance of Corn Ethanol: an Update,"<ref>{{cite web|url=http://www.transportation.anl.gov/pdfs/AF/265.pdf|title=The Energy Balance of Corn Ethanol: an Update|publisher=United States Department of Agriculture|accessdaymonth=21 May|accessyear=2007|author=Hosein Shapouri, James A. Duffield, and Michael Wang}}</ref> the energy returned on energy invested [[EROEI]] for ethanol made from corn in the U.S. is 1.34 (it yields 34% more energy than it takes to produce it). Input energy includes natural gas based fertilizers, farm equipment, transformation from corn or other materials, and transportation. However, other researchers report that the production of ethanol consumes more energy than it yields.<ref name=Pimentel2005>{{cite journal |author = Pimentel D, Patzek TW |year = 2005 |title = Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower |journal = Natural Resources Research |volume = 14 |issue = 1 |pages = 65-76 |doi = 10.1007/s11053-005-4679-8}}</ref><ref>{{cite web|url=http://www.news.cornell.edu/stories/July05/ethanol.toocostly.ssl.html|title=Cornell ecologist's study finds that producing ethanol and biodiesel from corn and other crops is not worth the energy|publisher=Cornell University|accessdaymonth=5 July|accessyear=2005|author=Lang, Susan S.}}</ref>

Lately criticism and controversy has been growing over the massive subsidies that some companies have been receiving for ethanol production,<ref name="bw0307">{{cite journal|journal=Business Week|title=Ethanol's Growing List of Enemies|url=http://www.businessweek.com/bwdaily/dnflash/content/mar2007/db20070316_016207.htm?campaign_id=rss_topStories|date=March 19, 2007|accessdate=2007-09-03|author=Moira Herbst}}</ref> including "the bulk of the more than $10 billion in subsidies to [[Archer-Daniels-Midland]] since 1980," according to the [[CATO institute]].<ref>{{cite web|url=http://www.cato.org/pub_display.php?pub_id=6079|title=Ethanol Keeps ADM Drunk On Tax Dollars.|publisher=CATO Institute|author=Doug Bandow|date=October 2, 1997|accessdate=2007-09-03}}</ref> Recent articles have also blamed subsidized ethanol production for the nearly 200% increase in milk prices since 2004,<ref name="cnn0607">{{cite journal|journal=CNNMoney.com|title=Corn and milk: A 1-2 inflation combo|url=http://money.cnn.com/2007/06/19/news/economy/commodity_prices/index.htm|date=June 19,2007|accessdate=2007-09-03|author=Jeff Cox}}</ref> although that is disputed by some.

Oil has historically had a much higher [[EROEI]] than agriculturally produced ethanol, especially from petroleum deposits accessible by land, but also from those that only offshore drilling rigs can reach. Apart from this, the amount of ethanol needed to run the United States, for example, is greater than its own farmland could produce, even if fields now used for food were converted for production of non-food-grade corn. It has been estimated that "if every bushel of U.S. [[corn]], [[wheat]], [[rice]] and [[soybean]] were used to produce ethanol, it would only cover about 4% of [[Energy_policy_of_the_United_States|U.S. energy needs]] on a net basis."<ref>{{cite news|url=http://www.bloomberg.com/apps/news?pid=20601039&refer=columnist_wasik&sid=aOS8e5kvDESE|title=Forget the Ethanol Myth -- Avoid Biofuel Bubble: John F. Wasik|date=July 23, 2007|publisher=Bloomberg.com|accessdate=2007-07-25}}</ref>

In the [[United States]], preferential regulatory and tax treatment of ethanol automotive fuels introduces complexities beyond its energy economics alone. North American automakers have in 2006 and 2007 promoted a blend of 85% ethanol and 15% gasoline, marketed as [[E85]], and their [[Flexible-fuel vehicle|flex-fuel vehicles]], ''e.g.'' [[General Motors|GM's]] "[http://www.livegreengoyellow.com/  Live Green, Go Yellow]" campaign.<ref name="autochannel">{{cite web|title=GM Announces E85 Fuel Card Promotion On FlexFuel Vehicles|url=http://www.theautochannel.com/news/2006/05/02/005502.html|accessdate=2007-09-04|publisher=The Auto Channel}}</ref> The apparent motivation is the nature of U.S. [[CAFE|Corporate Average Fuel Economy (CAFE)]] standards, which give an effective 54% fuel efficiency bonus to vehicles capable of running on 85% alcohol blends over vehicles not adapted to run on 85% alcohol blends.<ref>{{cite web | title = CAFE Credits for Flex Fuel Vehicles Undermine Improvements in Fuel Economy | publisher = Public Citizen | date = [[2006-09-27]] | url =http://www.citizen.org/autosafety/vehicles/enviro/articles.cfm?ID=15763| accessdate = 2007-09-03}}</ref> In addition to this auto manufacturer-driven impetus for 85% alcohol blends, the [[United States Environmental Protection Agency]] had authority to mandate that minimum proportions of oxygenates be added to automotive gasoline on regional and seasonal bases from 1992 until 2006 in an attempt to reduce air pollution, in particular [[ground-level ozone]] and [[smog]].<ref "epars">{{cite web|url=http://www.epa.gov/otaq/rfg_regs.htm|title= Regulations & Standards|publisher=United States Environmental Protection Agency|accessdate=2007-09-04}}</ref> As a consequence, much gasoline sold in the United States is blended with up to 10% of an unspecified oxygenating agent.<ref name="chevron">{{cite web|url=http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/4_oxygenated-gasoline/| title=Oxygenated Gasoline|publisher=Chevron Oil|accessdate=2007-09-04}}</ref> In [[United States|America]], incidents of methyl tert(iary)-butyl ether ([[MTBE]]) groundwater contamination in the majority of the 50 states,<ref>{{cite web|url=http://www.gao.gov/new.items/d02753t.pdf|title=MTBE Contamination from Underground Storage Tanks|publisher=United States General Accounting Office|date=May 21, 2002|accessdate=2007-10-09}}</ref> and the State of [[California]]'s ban on the use of MTBE as a gasoline additive has allowed ethanol to displace it as the most common fuel oxygenate.<ref name="epamtbe">{{cite web|url=http://www.epa.gov/mtbe/faq.htm|title=Methyl Tertiary Butyl Ether (MTBE)|publisher=United State Environmental Protection Agency|accessdate=2007-09-04}}</ref>

===Rocket fuel===
Ethanol was commonly used as fuel in early [[bipropellant]] [[rocket]] vehicles, in conjunction with an [[oxidizer]] such as liquid oxygen. The German [[V-2]] rocket of [[World War II]], credited with beginning the space age, used ethanol, mixed with water to reduce the combustion chamber temperature.<ref>{{cite web|url=http://www.daviddarling.info/encyclopedia/V/V-2.html|title=The Internet Encyclopedia of Science: V-2|author=David Darling}}</ref><ref name="braeunig">Braeunig, Robert A. [http://www.braeunig.us/space/propel.htm "Rocket Propellants."] (Website). Rocket & Space Technology, 2006. Retrieved on [[2007]]-[[08-23]].</ref> The V-2's design team helped develop U.S. rockets following World War II, including the ethanol-fueled [[Redstone (rocket)|Redstone rocket]], which launched the first U.S. satellite.<ref>[http://science.ksc.nasa.gov/history/rocket-history.txt "A Brief History of Rocketry."] NASA Historical Archive, via science.ksc.nasa.gov.</ref> Alcohols fell into general disuse as more efficient rocket fuels were developed.<ref name="braeunig" />

=== Alcoholic beverages ===
{{main|Alcoholic beverage}}

Ethanol is the principal psychoactive constituent in [[alcoholic beverage]]s, with [[depressant]] effects to the [[central nervous system]]. It has a complex mode of action and affects multiple systems in the brain.<ref>{{cite journal |author=Chastain G |title=Alcohol, neurotransmitter systems, and behavior |journal=The Journal of general psychology |volume=133 |issue=4 |pages=329–35 |year=2006 |pmid=17128954}}</ref> Similar psychoactives include those which also interact with [[GABA receptor]]s, such as [[gamma-hydroxybutyric acid]].<ref name="boggan2"/>

Alcoholic beverages vary considerably in their ethanol content and in the foodstuffs from which they are produced. Most alcoholic beverages can be broadly classified as [[fermented beverage]]s, beverages made by the action of yeast on sugary foodstuffs, or as [[distilled beverage]]s, beverages whose preparation involves concentrating the ethanol in fermented beverages by [[distillation]]. The ethanol content of a beverage is usually measured in terms of the volume fraction of ethanol in the beverage, expressed either as a percentage or in [[alcoholic proof]] units.

Fermented beverages can be broadly classified by the foodstuff from which they are fermented. [[Beer]]s are made from [[cereal grain]]s or other [[starch]]y materials, [[wine]]s and [[cider]]s from [[fruit juice]]s, and [[mead]]s from [[honey]]. Cultures around the world have made fermented beverages from numerous other foodstuffs, and local and national names for various fermented beverages abound.

Distilled beverages are made by distilling fermented beverages. Broad categories of distilled beverages include [[whiskey]]s, distilled from fermented cereal grains; [[brandy|brandies]], distilled from fermented fruit juices, and [[rum]], distilled from fermented [[molasses]] or [[sugarcane]] juice. [[Vodka]] and similar [[neutral grain spirits]] can be distilled from any fermented material (grain or [[potatoes]] are most common); these spirits are so thoroughly distilled that no tastes from the particular starting material remain. Numerous other spirits and liqueurs are prepared by infusing flavors from [[fruit]]s, [[herb]]s, and [[spice]]s into distilled spirits. A traditional example is [[gin]], which is created by infusing [[juniper]] berries into a neutral grain alcohol.

In a few beverages, ethanol is concentrated by means other than distillation. [[Applejack (beverage)|Applejack]] is traditionally made by [[freeze distillation]], by which water is frozen out of fermented [[apple cider]], leaving a more ethanol-rich liquid behind. [[Eisbier]] (more commonly, [[eisbock]]) is also freeze-distilled, with [[beer]] as the base beverage. [[Fortified wine]]s are prepared by adding brandy or some other distilled spirit to partially-fermented wine. This kills the yeast and conserves some of the [[sugar]] in grape juice; such beverages are not only more ethanol-rich, but are often sweeter than other wines.

Alcoholic beverages are sometimes used in cooking, not only for their inherent flavors, but also because the alcohol dissolves hydrophobic flavor compounds which water cannot.

=== Feedstock ===
{{main|Chemical derivatives of ethanol}}

Ethanol is an important industrial ingredient and has widespread use as a base chemical for other organic compounds. These include ethyl [[halide]]s, ethyl [[ester]]s, [[diethyl ether]], [[acetic acid]], [[butadiene]], and ethyl [[amine]]s.

=== Antiseptic use ===
Ethanol is used in medical wipes and in most common antibacterial [[hand sanitizer]] gels at a concentration of about 62% ([[percentage]] by weight, not volume) as an [[antiseptic]]. Ethanol kills organisms by denaturing their [[protein]]s and dissolving their [[lipid]]s and is effective against most [[bacterium|bacteria]] and [[fungus|fungi]], and many [[virus]]es, but is ineffective against bacterial [[spore]]s.<ref>{{cite journal |author=McDonnell G, Russell AD |title=Antiseptics and disinfectants: activity, action, and resistance |journal=Clin. Microbiol. Rev. |volume=12 |issue=1 |pages=147–79 |year=1999 |pmid=9880479 |url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9880479}}</ref>

=== Antidote ===
Although ethanol is a poison, it is sometimes used as an antidote for poisoning by other, more toxic alcohols, in particular [[methanol]]<ref name="cambridge">{{cite web|url=http://www-clinpharm.medschl.cam.ac.uk/pages/teaching/topics/poison/poison9.html| title=Methanol Poisoning|publisher=Cambridge University School of Clinical Medicine|accessdate=2007-09-04}}</ref> and [[ethylene glycol]].  Ethanol [[competitive inhibition|competes]] with other alcohols for the [[alcohol dehydrogenase]] enzyme, preventing metabolism into toxic [[aldehyde]] and [[carboxylic acid]] derivatives.<ref>{{cite journal |author=Barceloux DG, Bond GR, Krenzelok EP, Cooper H, Vale JA |title=American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning |journal=J. Toxicol. Clin. Toxicol. |volume=40 |issue=4 |pages=415–46 |year=2002 |pmid=12216995}}</ref>

=== Other uses ===
*Ethanol is easily [[soluble]] in [[water (molecule)|water]] and is a good [[solvent]]. Ethanol is less polar than water and used in [[perfume]]s, [[paint]]s and [[tincture]]s.
*Ethanol is also used in design and sketch art markers, such as [[Copic]], and [[Tria]].

==Metabolism and toxicology==
{{Main|Ethanol metabolism}}

{| align="right" width="250 px" class="wikitable"
! BAC (mg/dL) !! Symptoms<ref name="Pohorecky & Brick">Pohorecky, L.A., and J. Brick. (1988). "Pharmacology of ethanol." ''Pharmacology & Therapeutics'' '''36'''(3), 335-427.</ref>
|-
| 50 || Euphoria, talkativeness, relaxation
|-
| 100 || Central nervous system depression, impaired motor and sensory function, impaired cognition
|-
| &gt;140 || Decreased blood flow to brain
|-
| 300 || Stupefaction, possible unconsciousness
|-
| 400 || Possible death
|-
| &gt;550 || Expiration
|}

Pure ethanol is a tasteless liquid with a strong and distinctive odor that produces a characteristic heat-like sensation when brought into contact with the tongue or mucous membranes. Ethanol adds a distinctive taste to drinks. When applied to open wounds (as for disinfection) it produces a strong stinging sensation. Pure or highly concentrated ethanol may permanently damage living tissue on contact. Ethanol applied to unbroken skin cools the skin rapidly through evaporation.

Ethanol is a central nervous system depressant and has significant psychoactive effects in sublethal doses; for specifics, see [[Effects of alcohol on the body#Effects by dose|effects of alcohol on the body by dose]]. Based on its abilities to change the [[human consciousness]], ethanol is considered a [[drug]].<ref>[http://www.nlm.nih.gov/medlineplus/ency/article/001944.htm "Alcohol Use"] ''MedlinePlus Medical Encyclopedia'', U.S. National Library of Medicine and National Institutes of Health. Retrieved on [[2007]]-[[09-27]]</ref> Death from ethyl alcohol consumption is possible when blood alcohol level reaches 0.4%. A blood level of 0.5% or more is commonly fatal. Levels of even less than 0.1% can cause [[intoxication]], with unconsciousness often occurring at 0.3-0.4%.<ref name="yost"/> 

In America, about half of the deaths in car accidents occur in alcohol-related crashes.<ref>{{cite journal |author=Hingson R, Winter M |title=Epidemiology and consequences of drinking and driving |journal=Alcohol research & health : the journal of the National Institute on Alcohol Abuse and Alcoholism |volume=27 |issue=1 |pages=63–78 |year=2003 |pmid=15301401 |url=http://pubs.niaaa.nih.gov/publications/arh27-1/63-78.pdf}}</ref> There is no completely safe level of alcohol for driving, since the risk of a fatal [[car accident]] rises exponentially with the level of alcohol in the driver's blood.<ref>{{cite journal |author=Naranjo CA, Bremner KE |title=Behavioural correlates of alcohol intoxication |journal=Addiction |volume=88 |issue=1 |pages=25–35 |year=1993 |pmid=8448514}}</ref> However, most [[drunk driving]] laws governing the acceptable levels in the blood while driving or operating heavy machinery set typical upper limits of between 0.05% or 0.08%.

Ethanol interacts in harmful ways with a number of other drugs, including [[barbiturate]]s, [[benzodiazepine]]s, [[narcotic]]s, and [[phenothiazine]]s<ref name="yost">{{cite journal|url=http://www.postgradmed.com/issues/2002/12_02/yost1.htm|title=Acute care for alcohol intoxication|publisher=Postgraduate Medicine Online|author=David A. Yost, MD|volume=112|number=6|date=December 2002|accessdate=2007-09-29}}</ref>

===Metabolism===
Ethanol within the human body is converted into [[acetaldehyde]] by [[alcohol dehydrogenase]] and then into [[acetic acid]] by [[acetaldehyde dehydrogenase]]. The product of the first step of this breakdown, acetaldehyde,<ref name="boggan1">{{cite web|url=http://chemcases.com/alcohol/alc-06.htm|accessdate=2007-09-29|author=Dr. Bill Boggan|title= Metabolism of Ethyl Alcohol in the Body|publisher=Chemases.com}}</ref> is more toxic than ethanol. Acetaldehyde is linked to most of the clinical effects of alcohol. It has been shown to increase the risk of contracting cirrhosis of the liver,<ref name="boggan2">{{cite web|url=http://chemcases.com/alcohol/alc-07.htm|accessdate=2007-09-29|author=Dr. Bill Boggan|title= Effects of Ethyl Alcohol on Organ Function|publisher=Chemases.com}}</ref> multiple forms of cancer, and alcoholism.

===Magnitude of effect===
Some individuals have less effective forms of one or both of these enzymes, and can experience more severe symptoms from ethanol consumption than others. Conversely, those who have acquired ethanol [[drug tolerance|tolerance]] have a greater quantity of these enzymes, and metabolize ethanol more rapidly.<ref>{{cite journal |author=Agarwal DP, Goedde HW |title=Pharmacogenetics of alcohol metabolism and alcoholism |journal=Pharmacogenetics |volume=2 |issue=2 |pages=48–62 |year=1992 |pmid=1302043}}</ref>

The amount of ethanol in the body is typically quantified by [[blood alcohol content]] (BAC), the [[milligram]]s of ethanol per 100 [[milliliter]]s of blood. The table at right summarizes the symptoms of ethanol consumption. Small doses of ethanol generally produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgement. At higher dosages (BAC &gt; 100&nbsp;mg/dl), ethanol acts as a [[central nervous system]] [[depressant]], producing at progressively higher dosages, impaired sensory and motor function, slowed cognition, stupefaction, unconsciousness, and possible death.

Frequent use of alcoholic beverages has also been shown to be a major contributing factor in cases of elevated blood levels of [[triglycerides]].<ref>{{cite web|url=http://www.americanheart.org/presenter.jhtml?identifier=4778|title=Triglycerides
|accessdate=2007-09-04|publisher=American Heart Association}}</ref>

== See also ==
<div style="-moz-column-count:2; column-count:2;">
* [[Biodiesel]]
* [[Breathalyzer]]
* [[Cellulosic ethanol]]
* [[Cellulosic ethanol commercialization]]
* [[Corn liquor]]
* [[Denatured alcohol]]
* [[Ethanol (data page)]]
* [[Ethanol fuel]]
* [[Ethanol fuel in Brazil]]
* [[Effects of alcohol on the body]]
* [[Isopropyl alcohol]]
* [[List of energy topics]]
* [[2,2,2-Trichloroethanol]]
* [[1-Propanol]]
* [[Rubbing alcohol]]
* [[Timeline of alcohol fuel]]
* [[Corn Ethanol]]
</div>

== References ==
{{reflist|2}}

== Further reading ==
{{refbegin}}
* "Alcohol." (1911). In Hugh Chisholm (Ed.) ''Encyclopædia Britannica, 11th ed.'' [http://91.1911encyclopedia.org/A/AL/ALCOHOL.htm Online reprint]
* Lodgsdon, J.E. (1994). "Ethanol." In J.I. Kroschwitz (Ed.) ''Encyclopedia of Chemical Technology, 4th ed.'' vol. 9, pp. 812&ndash;860. New York: John Wiley & Sons.
* Smith, M.G., and M. Snyder. (2005). "Ethanol-induced virulence of ''Acinetobacter baumannii''". ''American Society for Microbiology meeting''. [[June 5]]-[[June 9]]. Atlanta.
* [http://sci-toys.com/ingredients/alcohol.html Sci-toys website explanation of US denatured alcohol designations]
* Boyce, John M., and Pittet Didier. ([[2003]]). [http://www.cdc.gov/handhygiene/ “Hand Hygiene in Healthcare Settings.”] [[Centers for Disease Control]], [[Atlanta, Georgia]], [[United States]].
* {{cite web|title= VS1000A Series In-Line Ethanol Sensors for the Beverage and BioFuel Industry|author=Rene Martinez VitalSensors Technologies LLC|url=http://www.vitalsensorstech.com/VitalSensors%20VS-1000A%20Ethanol%20Alcohol%20Sensor%20Data%20Sheet.pdf}}&mdash; Martinez describes the theory and practice of measuring brix on-line in beverages.
{{refend}}

==External links==
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc00/icsc0044.htm International Labour Organization] ethanol safety information
*[http://www.ceri.com/alcohol.htm Reducing the negative effects of alcohol by taking cysteine and vitamin C]
*[http://www.npi.gov.au/database/substance-info/profiles/35.html National Pollutant Inventory - Ethanol Fact Sheet]
*[http://www.ethanol-information.com/ Ethanol Information]
*[http://www.theethanolsource.com/ Ethanol Facts]
*[http://www.compchemwiki.org/index.php?title=Ethanol Coordinates of the ethanol molecule] on Computational Chemistry Wiki. Accessed on [[8 September]] [[2005]].
*[http://www.bluerhinos.co.uk/molview/indv.php?id=4 Molview from bluerhinos.co.uk] See Ethanol in 3D
*[http://webbook.nist.gov/cgi/cbook.cgi?Name=ethanol&Units=SI National Institute of Standards and Technology] chemical data on ethanol
*[http://www.distill.com/specs/US-2.html Specifications]
*[http://www.ethanolindia.net Ethanol Worldwide and India]
*[http://www.foodandfuelamerica.com FoodandFuelAmerica.com discusses the Food vs. Fuel debate with Ethanol]
*[http://www.unitedbioenergy.com United Bio Energy- (UBE) General information on ethanol plants and products. Also industry links]
*[http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:16236 ChEBI - biology related]
*[http://www.energysupplylogistics.com/ethanol Energy Supply Logistics Ethanol Plant/Terminal Database]
*[http://www.cbot.com/ Chicago Board of Trade] news and market data on ethanol futures

{{Alcohols}}
{{Antiseptics and disinfectants}}
{{Antidotes}}

[[Category:anatomical preservation]]
[[Category:Alcohol]]
[[Category:Alcohols]]
[[Category:Anxiolytics]]
[[Category:Drugs]]
[[Category:Rocket fuels]]
[[Category:Household chemicals]]
[[Category:Alcohol solvents]]
[[Category:Teratogens]]
[[Category:Disinfectants]]
[[Category:Oxygenates]]

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