Ethanol

Ethanol

Overview
{{Other uses|Ethanol (disambiguation)}} {{Redirect-distinguish|Grain alcohol|Neutral grain spirit}} {{Pp-move-indef|small=yes}} Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a [[volatility (chemistry)|volatile]], [[Flammability|flammable]], colorless liquid. It is a [[psychoactive drug]] and one of the oldest [[recreational drugs]].
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{{Other uses|Ethanol (disambiguation)}} {{Redirect-distinguish|Grain alcohol|Neutral grain spirit}} {{Pp-move-indef|small=yes}} Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a [[volatility (chemistry)|volatile]], [[Flammability|flammable]], colorless liquid. It is a [[psychoactive drug]] and one of the oldest [[recreational drugs]]. Best known as the type of [[alcohol]] found in [[alcoholic beverages]], it is also used in [[thermometers]], as a [[solvent]], and as a [[alcohol fuel|fuel]]. In common usage, it is often referred to simply as alcohol or [[Distilled beverage|spirits]]. Ethanol is a straight-chain alcohol, and its [[chemical formula|molecular formula]] is C2H5OH. Its [[empirical formula]] is [[Carbon|C]]2[[Hydrogen|H]]6[[Oxygen|O]]. An alternative notation is CH3–CH2–OH, which indicates that the carbon of a methyl group (CH3–) is attached to the carbon of a methylene group (–CH2–), which is attached to the oxygen of a [[Hydroxyl|hydroxyl group (–OH)]]. It is a constitutional [[isomer]] of [[dimethyl ether]]. Ethanol is often abbreviated as EtOH, using the common organic chemistry notation of representing the ethyl group (C2H5) with Et. The [[ethanol fermentation|fermentation]] of sugar into ethanol is one of the earliest [[organic reaction]]s employed by humanity. The intoxicating effects of ethanol consumption have been known since ancient times. In modern times, ethanol intended for industrial use is also produced from [[ethylene]]. Ethanol has widespread use as a solvent of substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products. It has a long history as a fuel for heat and light, and more recently as a fuel for [[internal combustion engine]]s. Ethanol is the [[systematic name]] defined by the [[IUPAC nomenclature of organic chemistry]] for a molecule with two carbon atoms (prefix "eth-"), having a single bond between them (suffix "-ane"), and an attached -OH group (suffix "-ol").

History

{{details|Distilled beverage}} Ethanol has been used by humans since prehistory as the intoxicating ingredient of [[alcoholic beverage]]s. Dried residue on 9,000-year-old pottery found in China imply that [[Neolithic]] people consumed alcoholic beverages. Although [[distillation]] was well known by the early Greeks and Arabs, the first recorded production of alcohol from distilled wine was by the [[School of Salerno]] alchemists in the 12th century. The first to mention absolute alcohol, in contrast with alcohol-water mixtures, was [[Raymond Lull]]. In 1796, Johann Tobias Lowitz obtained pure ethanol by filtering distilled ethanol through [[Activated carbon|activated 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 the structural formula of ethanol. It is one of the first structural formulas determined. Ethanol was first prepared synthetically in 1826 through the independent efforts of Henry Hennel in Great Britain and S.G. Sérullas in France. In 1828, [[Michael Faraday]] prepared ethanol by [[Acid catalysis|acid-catalyzed]] hydration of [[ethylene]], a process similar to current industrial ethanol synthesis. Ethanol was used as lamp fuel in the United States as early as 1840, but a tax levied on industrial alcohol during the [[American Civil War|Civil War]] made this use uneconomical. The tax was repealed in 1906. Original [[Ford Model T]] automobiles ran on ethanol until 1908. With the advent of [[Prohibition]] in 1920, ethanol fuel sellers were accused of being allied with [[moonshine]]rs, and ethanol fuel fell into disuse until late in the 20th century. {{Dubious|date=May 2011}}

Physical properties

[[File:Spiritusflamme mit spektrum.png|thumb|left|upright|Ethanol burning with its spectrum depicted]] Ethanol is a volatile, colorless liquid that has a slight odor. It burns with a smokeless blue flame that is not always visible in normal light. The physical 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 is a versatile solvent, [[miscible]] with water and with many organic solvents, including [[acetic acid]], [[acetone]], [[benzene]], [[carbon tetrachloride]], [[chloroform]], [[diethyl ether]], [[ethylene glycol]], [[glycerol]], [[nitromethane]], [[pyridine]], and [[toluene]]. It is also miscible with light aliphatic hydrocarbons, such as [[pentane]] and [[hexane]], and with aliphatic chlorides such as [[1,1,1-Trichloroethane|trichloroethane]] and [[tetrachloroethylene]]. Ethanol’s miscibility with water contrasts with that of longer-chain alcohols (five or more carbon atoms), whose water miscibility decreases sharply as the number of carbons increases. The miscibility of ethanol with [[alkane]]s is limited to alkanes up to [[undecane]], mixtures with [[dodecane]] and higher alkanes show a miscibility gap below a certain temperature (about 13 °C for dodecane). The miscibility gap tends to get wider with higher alkanes and the temperature for complete miscibility increases. Ethanol-water mixtures have less volume than the sum of their individual components at the given fractions. Mixing equal volumes of ethanol and water results in only 1.92 volumes of mixture. Mixing ethanol and water is [[exothermic]]. At 298 K, up to 777 J/mol are set free. Mixtures of ethanol and water form an [[azeotrope]] at about 89 mole-% ethanol and 11 mole-% water or a mixture of about 96 volume percent ethanol and 4% water at normal pressure and T = 351 K. This azeotropic composition is strongly temperature- and pressure-dependent and vanishes at temperatures below 303 K. NEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINE
Thermophysical properties of mixtures of ethanol with water and dodecane
[[File:Excess Volume Mixture of Ethanol and Water.png|275px]][[File:Mixing Enthalpy Mixture of Ethanol and Water.png|275px]][[File:Vapor-Liquid Equilibrium Mixture of Ethanol and Water.png|275px]]
Excess volume of the mixture of ethanol and water (volume contraction)Heat of mixing of the mixture of ethanol and waterVapor-liquid equilibrium of the mixture of ethanol and water (including [[azeotrope]])
[[File:Phase diagram ethanol water s l en.svg|275px]][[File:Liquid-Liquid Equilibrium (Miscibility Gap) Mixture of Ethanol and Dodecane.png|275px]]
Solid-liquid equilibrium of the mixture of ethanol and water (including [[eutecticum]])Miscibility gap in the mixture of dodecane and ethanol
NEWLINENEWLINE [[File:Ethanol-xtal-1976-3D-balls.png|thumb|300px|Hydrogen bonding in solid ethanol at −186 °C]] 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]]. [[Sodium chloride|Sodium]] and [[potassium chloride]]s are slightly soluble in ethanol. Because the ethanol molecule also has a nonpolar end, it will also dissolve nonpolar substances, including most [[essential oil]]s and numerous flavoring, coloring, and medicinal agents. 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 the wine’s 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. Mixtures of ethanol and water that contain more than about 50% ethanol are [[flammable]] and easily ignited. [[Alcoholic proof]] is a widely used measure of how much ethanol (i.e., alcohol) such a mixture contains. In the 18th century, proof was determined by adding a liquor (such as [[rum]]) to gunpowder. If the gunpowder still burned, that was considered to be “100 degrees proof” that it was “good” liquor — hence it was called “100 degrees proof”. Ethanol-water solutions that contain less than 50% ethanol may also be flammable if the solution is first heated. Some cooking methods 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 excess alcohol. Ethanol is slightly more refractive than water, having a [[refractive index]] of 1.36242 (at λ=589.3 nm and 18.35 °C).

Production

[[File:Ethanol Flasche.jpg|thumb|upright|94% denatured ethanol sold in a bottle for household use]] Ethanol is produced both as a [[petrochemical]], through the hydration of ethylene and, via biological processes, by [[fermentation (biochemistry)|fermenting]] sugars with [[yeast]]. Which process is more economical depends on prevailing prices of petroleum and grain feed stocks.

Ethylene hydration

Ethanol for use as an industrial feedstock or solvent (sometimes referred to as synthetic ethanol) is often made from [[petrochemical]] feed stocks, primarily by the [[acid]]-[[catalysis|catalyzed]] hydration of ethylene, represented by the [[chemical equation]] :[[ethylene|C2H4]](g) + H2O(g) → CH3CH2OH(l). The catalyst is most commonly [[phosphoric acid]], [[adsorption|adsorbed]] onto a porous support such as [[silica gel]] or [[diatomaceous earth]]. This catalyst was first used for large-scale ethanol production by the [[Shell Oil Company]] in 1947. The reaction is carried out with an excess of high pressure steam at 300 °C. In the U.S., this process was used on an industrial scale by [[Union Carbide Corporation]] and others; but now only [[LyondellBasell]] uses it commercially. In an older process, first practiced on the industrial scale in 1930 by Union Carbide, but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated [[sulfuric acid]] to produce [[ethyl sulfate]], which was [[hydrolysed]] to yield ethanol and regenerate the sulfuric acid: :C2H4 + [[sulfuric acid|H2SO4]] → [[ethyl sulfate|CH3CH2SO4H]] :[[ethyl sulfate|CH3CH2SO4H]] + [[H2O|H2O]] → CH3CH2OH + [[sulfuric acid|H2SO4]]

Fermentation

{{Main|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]] (e.g., [[Saccharomyces cerevisiae]]) [[metabolism|metabolize]] [[polysaccharide|sugar]] they produce ethanol and carbon dioxide. The chemical equations below summarize the conversion: :[[glucose|C6H12O6]] → 2 CH3CH2OH + 2 CO2 :[[sucrose|C12H22O11]] + H2O → 4 CH3CH2OH + 4 CO2 The process of culturing yeast under conditions to produce alcohol is called fermentation. This process is carried out at around 35–40 °C. Toxicity of ethanol to yeast limits the ethanol concentration obtainable by brewing; higher concentrations, therefore, are usually obtained by [[Fortified wine|fortification]] or [[distillation]]. The most ethanol-tolerant strains of yeast can survive up to approximately 15% ethanol by volume. 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.

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 Canadian firm [[Iogen Corp.|Iogen]] brought the first cellulose-based ethanol plant on-stream in 2004. 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 by-products, 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. Cellulose-bearing materials typically also contain other [[polysaccharide]]s, including [[hemicellulose]]. When undergoing hydrolysis, 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. On January 14, 2008, [[General Motors]] announced a partnership with Coskata, Inc. The goal is to produce cellulosic ethanol cheaply, with an eventual goal of US$1 per US gallon ($0.30/L) for the fuel. The partnership plans to begin producing the fuel in large quantity by the end of 2008. In June 2009, this goal is still ahead of the firm. By 2011 a full-scale plant will come on line, capable of producing {{convert|50|e6USgal|m3}} to {{convert|100|e6USgal|m3}} of ethanol a year (200–400 [[megalitre|ML]]/[[year|a]]).

Prospective technologies

[[File:SDethnl1.jpg|thumb|Ethanol plant in [[Turner County, South Dakota|Turner County]], [[South Dakota]]]] The [[anaerobic bacteria|anaerobic bacterium]] [[Clostridium]] ljungdahlii, 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|Fayetteville]], [[Arkansas]]. The BRI technology has been purchased by INEOS. Another prospective technology is the closed-loop ethanol plant. 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. There is also the issue of competition with use of corn for food production. However, the closed-loop ethanol plant attempts to address this criticism. In a closed-loop plant, renewable energy for distillation comes from [[Anaerobic digestion|fermented manure]], produced from cattle that have been fed the [[Distillers grains|DDSG]] by-products from grain ethanol production. The concentrated compost nutrients from manure are then used to fertilize the soil and grow the next crop of grain to start the cycle again. Such a process is expected to lower the fossil fuel consumption used during conversion to ethanol by 75%. An alternative technology allows for the production of [[biodiesel]] from distillers grain as an additional value product. 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.

Testing

[[File:EthanolMIRInfraredSpectra.PNG|thumb|300px|Infrared reflection spectra of liquid ethanol, showing the -OH band centered at ~3300 cm−1 and C-H bands at ~2950 cm−1.]] 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 cm−1. 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 volume (89.5 mole%). This mixture is an [[azeotrope]] with a boiling point of 78.1 °C, and cannot be further purified by distillation. Common methods for obtaining absolute ethanol include desiccation using adsorbents such as starch, corn grits, or [[zeolite]]s, which adsorb water preferentially, as well as [[azeotropic distillation]] and [[extractive distillation]]. Most ethanol fuel refineries use an adsorbent or zeolite to desiccate the ethanol stream. In another 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 °C (351.4 K). 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]]. 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]].

Denatured alcohol

{{Main|Denatured alcohol}} Pure ethanol and alcoholic beverages are heavily taxed, but ethanol has many uses that do not involve consumption by humans. To relieve the tax burden on these uses, most jurisdictions waive the tax when an agent has been added to the ethanol to render it unfit to drink. These include [[bitterant|bittering agents]] such as [[denatonium benzoate]] and toxins such as methanol, [[naphtha]], and [[pyridine]]. Products of this kind are called denatured alcohol.

Absolute ethanol

Absolute or anhydrous alcohol refers to ethanol with a low water content. There are various grades with maximum water contents ranging from 1% to ppm levels. Absolute alcohol is not intended for human consumption. If [[azeotropic distillation]] is used to remove water, it will contain trace amounts of the material separation agent (e.g. benzene). Absolute ethanol is used as a solvent for laboratory and industrial applications, where water will react with other chemicals, and as fuel alcohol. Spectroscopic ethanol is an absolute ethanol with a low absorbance in [[ultraviolet]] and visible light, fit for use as a solvent in [[ultraviolet-visible spectroscopy]]. Pure ethanol is classed as 200 [[proof (alcohol)|proof]] in the USA, equivalent to 175 degrees proof in the UK system.

Rectified spirits

Rectified spirit, an azeotropic composition containing 4% water, is used instead of anhydrous ethanol for various purposes. Wine spirits are about 188 [[proof (alcohol)|proof]]. The impurities are different from those in 190 proof laboratory ethanol.

Reactions

{{Details|Alcohol}} Ethanol is classified as a primary alcohol, meaning that the carbon its hydroxyl group attaches to has at least two hydrogen atoms attached to it as well. Many ethanol reactions occur at its [[hydroxyl]] group.

Ester formation

In the presence of acid catalysts, ethanol reacts with [[carboxylic acid]]s to produce ethyl [[ester]]s and water: :[[carboxylic acid|RCOOH]] + HOCH2CH3 → [[ester|RCOOCH2CH3]] + H2O This reaction, which is conducted on large scale industrially, requires the removal of the water from the reaction mixture as it is formed. Esters react in the presence of an acid or base to give back the alcohol and a salt. This reaction is known as [[saponification]] because it is used in the preparation of soap. Ethanol can also form esters with inorganic acids. [[Diethyl sulfate]] and [[triethyl phosphate]] are prepared by treating ethanol with sulfur trioxide and [[phosphorus pentoxide]] respectively. [[Diethyl sulfate]] is a useful ethylating agent 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 cause the dehydration of ethanol to form [[diethyl ether]] and other byproducts. If the dehydration temperature exceeds around 160 °C, [[ethylene]] will be the main product. Millions of kilograms of diethyl ether are produced annually using [[sulfuric acid]] catalyst: :2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120 °C)

Combustion

Complete [[combustion]] of ethanol forms [[carbon dioxide]] and [[water]] vapor: :C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g); (ΔHc = −1371 kJ/mol) specific heat = 2.44 kJ/(kg·K)

Acid-base chemistry

Ethanol is a neutral molecule and the [[pH]] of a solution of ethanol in water is nearly 7.00. Ethanol can be quantitatively converted to its [[conjugate base]], the [[Alkoxide|ethoxide]] ion (CH3CH2O), by reaction with an [[alkali metal]] such as [[sodium]]: :2 CH3CH2OH + 2 Na → 2 CH3CH2ONa + H2 or a very strong base such as [[sodium hydride]]: :CH3CH2OH + NaH → CH3CH2ONa + H2 The acidity of water and ethanol are nearly the same, as indicated by their [[Acid dissociation constant|pKa]] of 15.7 and 16 respectively. Thus, sodium ethoxide and [[sodium hydroxide]] exist in an equilbrium that is closely balanced: :CH3CH2OH + NaOH {{eqm}} CH3CH2ONa + H2O

Halogenation

Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are illustrative. Ethanol reacts with [[hydrogen halide]]s to produce [[haloalkane|ethyl halides]] such as [[ethyl chloride]] and [[ethyl bromide]] via an [[SN2 reaction|SN2 reaction]]: :CH3CH2OH + [[hydrogen chloride|HCl]] → CH3CH2Cl + H2O These reactions require a catalyst such as [[zinc chloride]]. HBr requires [[refluxing]] with a [[sulfuric acid]] catalyst. Ethyl halides can, in principle, also be produced by treating ethanol with more specialized [[Halogenation|halogenating agents]], such as [[thionyl chloride]] or [[phosphorus tribromide]]. :CH3CH2OH + SOCl2 → CH3CH2Cl + SO2 + HCl Upon treatment with halogens in the presence of base, ethanol gives the corresponding [[haloform]] (CHX3, where X = Cl, Br, I). This conversion is called the [[haloform reaction]]. " An intermediate in the reaction with chlorine is the [[aldehyde]] called [[chloral]]: :4 Cl2 + CH3CH2OH → CCl3CHO + 5 HCl

Oxidation

Ethanol can be oxidized to [[acetaldehyde]] and further oxidized to [[acetic acid]], depending on the reagents and conditions. This oxidation is of no importance industrially, but in the human body, these oxidation reactions are catalyzed by the [[enzyme]] [[liver alcohol dehydrogenase]]. The oxidation product of ethanol, acetic acid, is a nutrient for humans, being a precursor to [[acetyl CoA]], where the acetyl group can be spent as energy or used for biosynthesis.

As a fuel

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[[Energy density|Energy content]] of some fuels compared with ethanol:
Fuel type MJ/L MJ/kg [[octane rating|Research
octane
number]]
[[Wood fuel|Dry wood (20% moisture)]]~19.5
[[Methanol]]17.919.9108.7
[[ethanol fuel|Ethanol]]21.226.8108.6
[[E85]]
(85% ethanol, 15% gasoline)
25.233.2105
[[Liquefied natural gas]]25.3~55
[[Autogas]] ([[Liquified petroleum gas|LPG]])
(60% [[propane]] + 40% [[butane]])
26.850.
[[Aviation gasoline]]
(high-octane gasoline, not jet fuel)
33.546.8100/130 (lean/rich)
[[Alcohol fuel|Gasohol]]
(90% gasoline + 10% ethanol)
33.747.193/94
Regular gasoline34.844.4min. 91
Premium gasolinemax. 104
[[Diesel fuel|Diesel]]38.645.425
[[Charcoal]], extruded5023
NEWLINENEWLINE {{Main|Ethanol fuel}} The largest single use of ethanol is as a motor [[fuel]] and [[fuel additive]]. [[Brazil]] has the largest national fuel ethanol industry. [[Gasoline]] sold in Brazil contains at least 25% [[anhydrous]] ethanol. Hydrous ethanol (about 95% ethanol and 5% water) can be used as fuel in more than 90% of new cars sold in the country. Brazilian ethanol is produced from [[sugar cane]] and noted for high [[carbon sequestration]]. The US uses Gasohol (max 10% ethanol) and E85 (85% ethanol) ethanol/gasoline mixtures. [[File:Ethyl alcohol usp grade.jpg|thumb|upright|[[United States Pharmacopeia|USP]] grade ethanol for laboratory use.]] Ethanol may also be utilized as a [[rocket fuel]], and is currently in [[Light aircraft|lightweight]] [[Mark-III X-racer|rocket-powered racing aircraft]]. Australian law limits of the use of pure Ethanol sourced from Sugarcane waste to up to 10% in automobiles. It has been recommended that older cars (and vintage cars designed to use a slower burning fuel) have their valves upgraded or replaced. Ethanol as a fuel reduces harmful [[Motor vehicle emissions|tailpipe emissions]] of carbon monoxide, particulate matter, [[oxides of nitrogen]], and other ozone-forming pollutants. [[Argonne National Laboratory]] analyzed the greenhouse gas emissions of many different engine and fuel combinations. Comparing ethanol blends with gasoline alone, they showed reductions of 8% with the [[biodiesel]]/petrodiesel blend known as [[B20 (biodiesel)|B20]], 17% with the conventional [[E85]] ethanol blend, and that using [[cellulosic ethanol]] lowers emissions 64%. Ethanol combustion in an internal combustion engine yields many of the products of incomplete combustion produced by gasoline and significantly larger amounts of [[formaldehyde]] and related species such as acetaldehyde. This leads to a significantly larger photochemical reactivity that generates much more [[ground level ozone]]. These data have been assembled into The Clean Fuels Report comparison of fuel emissions and show that ethanol exhaust generates 2.14 times as much ozone as does gasoline exhaust.{{citation needed|date=March 2011}} When this is added into the custom Localised Pollution Index (LPI) of The Clean Fuels Report the local pollution (pollution that contributes to smog) is 1.7 on a scale where gasoline is 1.0 and higher numbers signify greater pollution. The [[California Air Resources Board]] formalized this issue in 2008 by recognizing control standards for formaldehydes as an emissions control group, much like the conventional [[NOx]] and Reactive Organic Gases (ROGs). [[File:Sao Paulo ethanol pump 04 2008 74 zoom.jpg|thumb|left|Ethanol pump station in [[São Paulo|São Paulo, Brazil]] where the fuel is available commercially.]] World production of ethanol in 2006 was {{convert|51|GL|usgal}}, with 69% of the world supply coming from Brazil and the United States. More than 20% of Brazilian cars are able to use 100% ethanol as fuel, which includes ethanol-only engines and [[Flexible-fuel vehicle|flex-fuel]] engines. Flex-fuel engines in Brazil are able to work with all ethanol, all gasoline or any mixture of both. In the US flex-fuel vehicles can run on 0% to 85% ethanol (15% gasoline) since higher ethanol blends are not yet allowed or efficient. 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 used in power plants as a surprisingly efficient fuel to produce electricity.{{Citation needed|date=January 2010}} [[File:Ethanol Car.jpg|thumb|left|A [[Ford Taurus]] "fueled by clean burning ethanol" owned by [[New York City]].]] The United States fuel ethanol industry is based largely on [[Maize|corn]]. According to the Renewable Fuels Association, as of October 30, 2007, 131 grain ethanol bio-refineries in the United States have the capacity to produce {{convert|7.0|e9USgal|m3}} of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add {{convert|6.4|e9USgal|m3}} of new capacity in the next 18 months. Over time, it is believed that a material portion of the ≈{{convert|150|e9USgal|m3|adj=on}} per year market for gasoline will begin to be replaced with fuel ethanol. [[File:USPS-E85 fuel-St Paul-20070127.jpg|thumb|[[United States Postal Service]] vehicle running on [[E85]], a "flex-fuel" blend in [[Saint Paul, Minnesota|Saint Paul]], [[Minnesota]].]] One problem with ethanol is its high [[miscibility]] with water, which means that it cannot be efficiently shipped through modern [[Pipeline transport|pipelines]], like liquid hydrocarbons, over long distances. Mechanics also have seen increased cases of damage to small engines, in particular, the carburetor, attributable to the increased water retention by ethanol in fuel.

Alcoholic beverages

{{Main|Alcoholic beverage}} Ethanol is the principal psychoactive constituent in [[alcoholic beverage]]s, with [[depressant]] effects on the [[central nervous system]]. It has a complex mode of action and affects multiple systems in the brain, the most notable one being its agonistic action on the [[GABA receptors]]. Similar psychoactives include those that also interact with [[GABA receptors]], such as [[gamma-hydroxybutyric acid]] (GHB). Ethanol is metabolized by the body as an energy-providing nutrient, as it metabolizes into [[acetyl CoA]], an intermediate common with glucose and [[fatty acid]] metabolism that can be used for energy in the [[citric acid cycle]] or for biosynthesis. Alcoholic beverages vary considerably in ethanol content and in foodstuffs they are produced from. Most alcoholic beverages can be broadly classified as [[fermented beverage]]s, beverages made by the action of yeast on sugary foodstuffs, or [[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 they are fermented from. [[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, tomatoes or [[potato]]es 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. [[Ice beer]] (also known by the [[German language|German]] term Eisbier or [[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 not only are 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. Just as industrial ethanol is used as feedstock for the production of industrial acetic acid, alcoholic beverages are made into culinary/household [[vinegar]]: [[vinegar#Wine|Wine]] and [[cider vinegar]] are both named for their respective source alcohols, whereas [[malt vinegar]] is derived from beer.

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, ethyl [[amine]]s, and to a lesser extent [[butadiene]].

Antiseptic

Ethanol is used in medical wipes and in most common antibacterial [[hand sanitizer]] gels at a concentration of about 62% v/v as an [[antiseptic]]. Ethanol kills organisms by [[Denaturation (biochemistry)|denaturing]] their [[protein]]s and dissolving their [[lipid]]s and is effective against most [[bacteria]] and [[fungus|fungi]], and many [[virus]]es, but is ineffective against bacterial [[spore]]s.

Treatment for poisoning by other alcohols {{anchor|Antidote for methanol poisoning}}

Ethanol is sometimes used to treat poisoning by other, more toxic alcohols, in particular [[methanol]] and [[ethylene glycol]]. Ethanol [[competitive inhibition|competes]] with other alcohols for the [[alcohol dehydrogenase]] enzyme, lessening metabolism into toxic [[aldehyde]] and [[carboxylic acid]] derivatives, and reducing one of the more serious toxic effect of the glycols to [[crystallization|crystallize]] in the [[kidneys]].

Solvent

Ethanol is [[miscible]] with [[water (molecule)|water]] and is a good general purpose [[solvent]]. It is found in [[paint]]s, [[tincture]]s, markers, and personal care products such as perfumes and deodorants. It may also be used as a solvent in cooking, such as in [[vodka sauce]].

Historical uses

Before the development of modern medicines, ethanol was used for a variety of medical purposes. It has been known to be used as a [[truth drug]] (as hinted at by the maxim "[[in vino veritas]]"), as medicine for [[Depression (mood)|depression]] and as an [[anesthetic]].{{Citation needed|date=May 2010}} Ethanol was commonly used as fuel in early [[bipropellant]] [[rocket]] (liquid propelled) 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 25% of water to reduce the combustion chamber temperature. 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. Alcohols fell into general disuse as more efficient rocket fuels were developed.

Pharmacology

Ethanol binds to [[Acetylcholine receptor|acetylcholine]], [[GABA receptor|GABA]], [[Serotonin receptor|serotonin]], and [[NMDA receptor]]s. The removal of ethanol through oxidation by [[alcohol dehydrogenase]] in the [[liver]] from the human body is limited. Hence, the removal of a large concentration of alcohol from [[blood]] may follow [[Zero order kinetics|zero-order kinetics]]. This means that alcohol leaves the body at a constant rate, rather than having an elimination [[Biological half-life|half-life]]. Also, the rate-limiting steps for one substance may be in common with other substances. For instance, the blood alcohol concentration can be used to modify the biochemistry of [[methanol]] and [[ethylene glycol]]. In this way the oxidation of methanol to the [[toxic]] [[formaldehyde]] and [[formic acid]] in the (human body) can be prevented by giving an appropriate amount of ethanol to a person having [[eating|ingested]] methanol. Note that methanol is very toxic and causes [[blindness]] and death. A person having ingested [[ethylene glycol]] can be treated in the same way.

Drug effects

Pure ethanol will irritate the skin and eyes. Nausea, [[vomiting]] and intoxication are symptoms of ingestion. Long-term use by ingestion can result in serious liver damage. Atmospheric concentrations above one in a thousand are above the European Union [[Occupational exposure limit]]s.

Short-term

{{Main|Short-term effects of alcohol}} NEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINENEWLINE
BAC (g/L) BAC
(% v/v)
Symptoms
0.50.05%Euphoria, talkativeness, relaxation
10.1 %Central nervous system depression, nausea, possible vomiting, impaired motor and sensory function, impaired cognition
>1.4 >0.14%Decreased blood flow to brain
30.3%Stupefaction, possible unconsciousness
40.4%Possible death
>5.5 >0.55%Death
NEWLINENEWLINE

Effects on the central nervous system

Ethanol is a central nervous system depressant and has significant psychoactive effects in sublethal doses; for specifics, see [[Effects of alcohol on the body#Effect by dosage|"Effects of alcohol on the body by dose"]]. Based on its abilities to change the [[human consciousness]], ethanol is considered a [[psychoactive]] [[drug]]. 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 [[Alcohol intoxication|intoxication]], with unconsciousness often occurring at 0.3–0.4%. The amount of ethanol in the body is typically quantified by [[blood alcohol content]] (BAC), which is here taken as weight of ethanol per unit volume of blood. The table at right summarizes the symptoms of ethanol consumption. Small doses of ethanol, in general, produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. At higher dosages (BAC > 1 g/L), 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. Ethanol acts in the central nervous system by binding to the [[GABA-A]] receptor, increasing the effects of the inhibitory [[neurotransmitter]] [[GABA]] (i.e., it is a [[positive allosteric modulator]]). Prolonged heavy consumption of alcohol can cause significant permanent damage to the brain and other organs. See [[Alcohol consumption and health]]. In USA, about half of the deaths in car accidents occur in alcohol-related crashes. The risk of a fatal [[car accident]] increases exponentially with the level of alcohol in the driver's blood. Most [[drunk driving]] laws governing the acceptable levels in the blood while driving or operating heavy machinery set typical upper limits of [[blood alcohol content]] (BAC) between 0.05% and 0.08%.{{Citation needed|date=May 2010}} Discontinuing consumption of alcohol after several years of heavy drinking can also be fatal. Alcohol withdrawal can cause anxiety, autonomic dysfunction, seizures, and hallucinations. [[Delirium tremens]] is a condition that requires people with a long history of heavy drinking to undertake an [[alcohol detoxification]] regimen.

Effects on metabolism

{{Main|Ethanol metabolism|Alcohol dehydrogenase}} Ethanol within the human body is converted into acetaldehyde by [[alcohol dehydrogenase]] and then into the [[acetyl]] in [[acetyl CoA]] by [[acetaldehyde dehydrogenase]]. [[Acetyl CoA]] is the final product of both carbohydrate and fat metabolism, where the acetyl can be further used to produce energy or for biosynthesis. As such, ethanol is a nutrient. However, the product of the first step of this breakdown, acetaldehyde, 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 developing cirrhosis of the liver, multiple forms of cancer, and [[alcoholism]].

Drug interactions

Ethanol can intensify the sedation caused by other [[central nervous system]] [[depressant]] drugs such as [[barbiturate]]s, [[benzodiazepine]]s, [[opioid]]s, [[phenothiazine]]s, and [[anti-depressants]].

Magnitude of effects

Some individuals have less effective forms of one or both of the metabolizing enzymes, and can experience more severe symptoms from ethanol consumption than others. However, those having acquired [[alcohol tolerance]] have a greater quantity of these enzymes, and metabolize ethanol more rapidly.

Other effects

Frequent drinking of alcoholic beverages has been shown to be a major contributing factor in cases of elevated blood levels of [[triglycerides]]. Ethanol is not a [[carcinogen]]. However, the first metabolic product of ethanol, [[acetaldehyde]], is toxic, [[mutagen]]ic, and carcinogenic.

Natural occurrence

Ethanol is a byproduct of the metabolic process of yeast. As such ethanol will be present in any yeast habitat. Ethanol can commonly be found in overripe fruit. Ethanol produced by symbiotic yeast can be found in [[palm wine|Bertam Palm]] blossoms. Although some species such as the [[Pentailed Treeshrew]] exhibit ethanol seeking behaviors, most show no interest or avoidance of food sources containing ethanol. Ethanol is also produced during the germination of many plants as a result of natural [[anerobiosis]]. Ethanol has been detected in [[outer space]], forming an icy coating around dust grains in [[interstellar cloud]]s.

See also

{{Portal|Pharmacy and Pharmacology}} {{div col|colwidth=15em}} *[[2,2,2-Trichloroethanol]] *[[Biodiesel]] *[[Breathalyzer]] *[[Butanol fuel]] *[[Cellulosic ethanol commercialization]] *[[Ethanol (data page)]] *[[Ethenol]] *[[Ethynol]] *[[Isopropyl alcohol]] *[[Outline of energy]] *[[Propan-1-ol]] *[[Rubbing alcohol]] *[[Timeline of alcohol fuel]] {{div col end}}

Further reading

*The [[National Institute on Alcohol Abuse and Alcoholism]] maintains a database of alcohol-related health effects. [http://etoh.niaaa.nih.gov/Archive.htm ETOH Archival Database (1972–2003)] Alcohol and Alcohol Problems Science Database. *Boyce, John M., and Pittet Didier. (2003). [http://cdc.gov/handhygiene/ “Hand Hygiene in Healthcare Settings.”] [[Centers for Disease Control]], [[Atlanta, Georgia|Atlanta]], [[Georgia (U.S. state)|Georgia]], United States. *[http://sci-toys.com/ingredients/alcohol.html Sci-toys website explanation of US denatured alcohol designations] *Smith, M.G., and M. Snyder. (2005). "Ethanol-induced virulence of Acinetobacter baumannii". American Society for Microbiology meeting. June 5 – June 9. Atlanta.

External links

{{Commons}} *[http://www.inchem.org/documents/icsc/icsc/eics0044.htm International Labour Organization] ethanol safety information *[http://www.npi.gov.au/substances/ethanol/index.html National Pollutant Inventory – Ethanol Fact Sheet] *[http://webbook.nist.gov/cgi/cbook.cgi?Name=ethanol&Units=SI National Institute of Standards and Technology] chemical data on ethanol *[http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:16236 ChEBI – biology related] *[http://cbot.com/ Chicago Board of Trade] news and market data on ethanol futures *Calculation of [http://ddbonline.ddbst.de/AntoineCalculation/AntoineCalculationCGI.exe?component=Ethanol vapor pressure], [http://ddbonline.ddbst.de/DIPPR105DensityCalculation/DIPPR105CalculationCGI.exe?component=Ethanol liquid density], [http://ddbonline.ddbst.de/VogelCalculation/VogelCalculationCGI.exe?component=Ethanol dynamic liquid viscosity], [http://ddbonline.ddbst.de/DIPPR106SFTCalculation/DIPPR106SFTCalculationCGI.exe?component=Ethanol surface tension] of ethanol *[http://druginfo.nlm.nih.gov/drugportal/dpdirect.jsp?name=Ethanol U.S. National Library of Medicine: Drug Information Portal – Ethanol] *[http://www.ethanolhistory.com Ethanol History] A look into the history of ethanol {{Alcohols}} {{Alcoholic beverages}} {{Antiseptics and disinfectants}} {{Antidotes}} {{Neurotoxins}} {{GABAergics}} {{Good article}}