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Ethanol
Ethanol-2D-skeletal Ethanol-3D-vdW
General
Systematic name Ethanol
Other names Ethyl alcohol,
grain alcohol,
hydroxyethane,
moonshine,
drinking alcohol,
EtOH
Molecular formula C2H5OH
SMILES CCO
Molar mass 46.06844(232) g/mol
Appearance colorless clear liquid
CAS number [64-17-5]
Properties
Density and phase 0.789 g/cm³, liquid
Solubility in water Fully miscible
Melting point −114.3 °C (158.8 K)
Boiling point 78.4 °C (351.6 K)
Acidity (pKa) 15.9 (H+ from OH group)
Viscosity 1.200 mPa·s (cP) at 20.0 °C
Dipole moment 5.64 fC·fm (1.69 D) (gas)
Hazards
MSDS External MSDS
EU classification Flammable (F)
NFPA 704
NFPA 704
3
0
0
 


R-phrases R11
S-phrases
  1. REDIRECT Template:(S2)

, S7 , S16

Flash point 286.15 K (13 °C or 55.4 °F)
Flammable limits
in air (by volume)
3.28% - 18.95%
RTECS number KQ6300000
Supplementary data page
Structure & properties n, εr, etc.
Thermodynamic data Phase behavior
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Related alcohols Methanol, 1-Propanol
Other heteroatoms Ethylamine, Ethyl chloride,
Ethyl bromide, Ethanethiol
Substituted ethanols Ethylene glycol, Ethanolamine,
2-Chloroethanol
Other compounds Acetaldehyde, Acetic acid
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Ethanol, also known as ethyl alcohol, drinking alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound with a distinctive perfume-like odor, and is best known as the alcohol found in alcoholic beverages. In common usage, it is often referred to simply as alcohol. Its molecular formula is variously represented as EtOH, CH3CH2OH, C2H5OH or as its empirical formula C2H6O.

Physical propertiesEdit

Ethanol's hydroxyl group is able to participate in hydrogen bonding. At the molecular level, liquid ethanol consists of hydrogen-bonded pairs of ethanol molecules (dimers); this phenomenon renders ethanol 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 has a refractive index of 1.3614, and is a versatile solvent. It is miscible with water and with most organic liquids, including nonpolar liquids such as aliphatic hydrocarbons. Due to the hydrogen bonding properties of ethanol, it will absorb water from the air when left. Among ionic compounds, many monovalent salts are at least somewhat soluble in ethanol, with salts of large, polarizable ions being more soluble than salts of smaller ions. Most salts of polyvalent ions are practically insoluble in ethanol. Ethanol is used as a solvent in dissolving medicines, food flavorings and colorings that do not dissolve easily in water. Once the non-polar material is dissolved in the ethanol, water can be added to prepare a solution that is mostly water. The ethanol molecule has a hydrophilic OH group that helps it dissolve polar molecules and ionic substances. The short, hydrophobic hydrocarbon chain can attract non-polar molecules. Thus ethanol can dissolve both polar and non-polar substances.

Chemistry Edit

Ethanol-3d-stick-structure

Chemical formula of ethanol, (C is carbon, the dash is a single bond, H is hydrogen, O is oxygen)

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

Acid-base chemistry

Ethanol's hydroxyl proton is weakly acidic, having a pKa of only 15.9, compared to water's 15.7[1] (Ka of ethanol is a measure of \scriptstyle \frac {[C_2H_5O^-][H^+]} {[C_2H_5OH]}. Note that Ka of water is derived by dividing water's dissociation constant, \scriptstyle[H^+][OH^-] = 1.0 \times 10^{-14} moles2/liter, by its molar density of 55.5 moles/liter). Ethanol can be quantitatively converted to its conjugate base, the ethoxide ion (CH3CH2O), by reaction with an alkali metal such as sodium. This reaction evolves hydrogen gas:

2CH3CH2OH + 2Na → 2CH3CH2ONa + H2
Nucleophilic substitution

In aprotic solvents, ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl chloride and ethyl bromide via nucleophilic substitution:

CH3CH2OH + HClCH3CH2Cl + H2O
CH3CH2OH + HBrCH3CH2Br + H2O

Ethyl halides can also be produced by reacting ethanol by more specialized halogenating agents, such as thionyl chloride for preparing ethyl chloride, or phosphorus tribromide for preparing ethyl bromide.

Esterification

Under acid-catalysed conditions, ethanol reacts with carboxylic acids to produce ethyl esters and water:

RCOOH + HOCH2CH3RCOOCH2CH3 + H2O

The reverse reaction, hydrolysis of the resulting ester back to ethanol and the carboxylic acid, limits the extent of reaction, and high yields are unusual unless water can be removed from the reaction mixture as it is formed. Esterification can also be carried out using more a reactive derivative of the carboxylic acid, such as an acyl chloride or acid anhydride. A very common ester of ethanol is ethyl acetate, found in nailpolish remover.

Ethanol can also form esters with inorganic acids. Diethyl sulfate and triethyl phosphate, prepared by reacting ethanol with 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 acids, such as sulfuric acid, can catalyse ethanol's dehydration to form either diethyl ether or ethylene:

2 CH3CH2OH → CH3CH2OCH2CH3 + H2O
CH3CH2OH → H2C=CH2 + H2O

Although sulfuric acid catalyses this reaction, the acid is diluted by the water that is formed, which makes the reaction inefficient. Which product, diethyl ether or ethylene, predominates depends on the precise reaction conditions.

Oxidation

Ethanol can be oxidized to acetaldehyde, and further oxidized to acetic acid. In the human body, these oxidation reactions are catalysed by enzymes. 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 overoxidation to acetic acid, by reacting it with pyridinium chromic chloride.

Combustion
Chemistry, Combustion of Ethanol 002

Ethanol combusting in the confines of an evaporating dish

Combustion of ethanol forms carbon dioxide and water:

C2H5OH + 3 O2 → 2 CO2 + 3 H2O

Production Edit

Ethanol Flasche

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 fermenting sugars with yeast.

Ethylene hydration Edit

Ethanol for use as industrial feedstock is most often made from petrochemical feedstocks, typically by the acid-catalyzed hydration of ethene, represented by the chemical equation

C2H4 + H2O → CH3CH2OH

The catalyst is most commonly phosphoric acid, 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.[2] Solid catalysts, mostly various metal oxides, have also been mentioned in the chemical literature.

In an older process, first practiced on the industrial scale in 1930 by Union Carbide,[3] but now almost entirely obsolete, ethene was hydrated indirectly by reacting it with concentrated sulfuric acid to produce ethyl sulfate, which was then hydrolysed to yield ethanol and regenerate the sulfuric acid:

C2H4 + H2SO4CH3CH2SO4H
CH3CH2SO4H + H2O → CH3CH2OH + H2SO4

Fermentation Edit

Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of yeast (most importantly, Saccharomyces cerevisiae) metabolize sugar in the absence of oxygen, they produce ethanol and carbon dioxide. The overall chemical reaction conducted by the yeast may be represented by the chemical equation

C6H12O6 → 2 CH3CH2OH + 2 CO2

The process of culturing yeast under conditions to produce alcohol is referred to as brewing. Brewing can only produce relatively dilute concentrations of ethanol in water; concentrated ethanol solutions are toxic to yeast. The most ethanol-tolerant strains of yeast can survive in up to about 15% ethanol (by volume).

During the fermentation process, it is important to prevent oxygen from getting to the ethanol, since otherwise the ethanol would be oxidised to acetic acid (vinegar). Also, in the presence of oxygen, the yeast would undergo aerobic respiration to produce just carbon dioxide and water, without producing ethanol.

In order to produce ethanol from starchy materials such as cereal grains, the starch must first be broken down into sugars. In brewing beer, this has traditionally been accomplished allowing the grain to germinate, or malt. In the process of germination, the seed produces enzymes that can break its starches into sugars. For fuel ethanol, this hydrolysis of starch into glucose is accomplished more rapidly by treatment with dilute sulfuric acid, fungal amylase enzymes, or some combination of the two.

FeedstocksEdit

Currently the main feedstock in the United States for the production of ethanol is corn.[How to reference and link to summary or text] Approximately 2.8 gallons of ethanol (10 liters) are produced from one bushel of corn (35 liters). While much of the corn turns into ethanol, some of the corn also yields by-products such as DDGS (distillers dried grains with solubles) that can be used to fulfill a portion of the diet of livestock. A bushel of corn produces about 18 pounds of DDGS.[4] Critics of ethanol as fuel decry the use of corn to produce ethanol because corn is an energy-intensive crop that requires petroleum-derived fertilizers; however, using corn to produce alcohol could save farmers additional petroleum if the farmers are feeding the byproduct to livestock and if the excrement from the animals is then used as fertilizer for the corn [Lynn Ellen Doxon; The Alcohol Fuel Handbook]. Although most of the fermentation plants have been built in corn-producing regions, sorghum is also an important feedstock for ethanol production in the Plains states. Pearl millet is showing promise as an ethanol feedstock for the southeastern U.S.

Trials of new crops, such as agricultural residues, wood wastes, and various grasses, show much lower yields using conventional, commercialized processes.[How to reference and link to summary or text] These crops are cellulosic rather than starchy, and have fewer accessible sugars for fermentation.[How to reference and link to summary or text] Newer, more complex processes are necessary to release plant sugars, primarily by disrupting lignin networks.[How to reference and link to summary or text] However, the appeal of such crops is their lower requirement for fertilizer and other inputs, and in some cases lower cost or higher availability as "waste" products.[How to reference and link to summary or text]

The dominant ethanol feedstock in warmer regions is sugarcane.[How to reference and link to summary or text] The directly-accessible sugars simplify the fermentation process.[How to reference and link to summary or text] In temperate regions, this accessibility has been somewhat replicated by selective breeding of the sugar beet.[How to reference and link to summary or text]

In some parts of Europe, particularly France and Italy, wine is used as a feedstock due to massive oversupply.[5] Japan is hoping to use rice wine (sake) as an ethanol source.[6]

At petroleum prices like those that prevailed through much of the 1990s, ethylene hydration was a decidedly more economical process than fermentation for producing purified ethanol. Later increases in petroleum prices, coupled with perennial uncertainty in agricultural prices, make forecasting the relative production costs of fermented versus petrochemical ethanol difficult..

TestingEdit

In breweries and biofuel plants, the quantity of ethanol present is measured using one of two methods. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the CH band at 2900cm-1. This method uses a relatively inexpensive solid state sensor that compares the CH band with a reference band to calculate the ethanol content. This 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 gravity during fermentation is used to derive the alcohol content. This is an inexpensive and indirect method but has a long history in the beer brewing industry.

Purification Edit

Ethanol near IR spectrum

Near infrared spectrum of liquid ethanol.

The product of either ethylene hydration or brewing is 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%). The mixture of 95.6% ethanol and 4.4% water (percentage by weight) is an azeotrope with a boiling point of 78.2 °C, and cannot be further purified by distillation. Therefore, 95% ethanol in water is a fairly common solvent.

After distillation ethanol can be further purified by "drying" it using lime or salt. When lime (calcium oxide) is mixed with the water in ethanol, calcium hydroxide forms. The calcium hydroxide can then be separated from the ethanol. Dry salt will dissolve some of the water content of the ethanol as it passes through, leaving a purer alcohol.[7]

Several approaches are used to produce absolute ethanol. The ethanol-water azeotrope can be broken by the addition of a small quantity of benzene. Benzene, ethanol, and water form a ternary azeotrope with a boiling point of 64.9 °C. Since this azeotrope is more volatile than the ethanol-water azeotrope, it can be fractionally distilled out of the ethanol-water mixture, extracting essentially all of the water in the process. The bottoms from such a distillation is anhydrous ethanol, with several parts per million residual benzene. Benzene is toxic to humans, and cyclohexane has largely supplanted benzene in its role as the entrainer in this process.

Alternatively, a molecular sieve can be used to selectively absorb the water from the 95.6% ethanol solution. Synthetic zeolite in pellet form can be used, as well as a variety of plant-derived absorbents, including cornmeal, straw, and sawdust. The zeolite bed can be regenerated essentially an unlimited number of times by drying it with a blast of hot carbon dioxide. Cornmeal and other plant-derived absorbents cannot readily be regenerated, but where ethanol is made from grain, they are often available at low cost. Absolute ethanol produced this way has no residual benzene, and can be used to fortify port and sherry in traditional winery operations. Membranes can also be used to separate ethanol and water. The membrane can break the water-ethanol azeotrope because separation is not based on vapor-liquid equilibria. Membranes are often used in the so-called hybrid membrane distillation process. This process uses a pre-concentration distillation column as first separating step. The further separation is then accomplished with a membrane operated either in vapor permeation or pervaporation mode. Vapor permeation uses a vapor membrane feed and pervaporation uses a liquid membrane feed.

At pressures less than atmospheric pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures, and at pressures less than 70 torr (9.333 kPa) , there is no azeotrope, and it is possible to distill absolute ethanol from an ethanol-water mixture. While vacuum distillation of ethanol is not presently economical, pressure-swing distillation is a topic of current research. In this technique, a reduced-pressure distillation first yields an ethanol-water mixture of more than 95.6% ethanol. Then, fractional distillation of this mixture at atmospheric pressure distills off the 95.6% azeotrope, leaving anhydrous ethanol at the bottoms.

Cellulosic EthanolEdit

Main article: Cellulosic ethanol

Glucose for fermentation into ethanol can also be obtained from cellulose. Until recently, however, the cost of the cellulase enzymes that could hydrolyse cellulose has been prohibitive. The Canadian firm Iogen brought the first cellulose-based ethanol plant on-stream in 2004.[8] The primary consumer thus far has been the Canadian government, which, along with the United States government (particularly the Department of Energy's National Renewable Energy Laboratory), has invested millions of dollars into assisting the commercialization of cellulosic ethanol. Realization of this technology would turn a number of cellulose-containing agricultural byproducts, such as corncobs, straw, and sawdust, into renewable energy resources.

Other enzyme companies are developing genetically engineered fungi which would produce large volumes of cellulase, xylanase and hemicellulase enzymes which can be utilized to convert agricultural residues such as corn stover, distiller grains, wheat straw and sugar cane bagasse and energy crops such as Switchgrass into fermentable sugars which may be used to produce cellulosic ethanol.[9]

Cellulosic materials typically contain, in addition to cellulose, other polysaccharides, including hemicellulose. When hydrolysed, hemicellulose breaks down 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 metabolize xylose and so improve the ethanol yield from cellulosic material. [10]

Prospective technologies Edit

The 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 fuels 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.[11]

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. 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.[12] However, general thermodynamic considerations indicate that the total efficiency of such plants, in combination with the production of cellulose/sugar, will remain relatively low.

Types of ethanolEdit

Denatured alcohol Edit

Main article: Denatured alcohol

In most jurisdictions, the sale of ethanol, as a pure substance, or in the form of alcoholic beverages, is heavily taxed. In order to relieve non-beverage industries of this tax burden, governments specify formulations for denatured alcohol, which consists of ethanol blended with various additives to render it unfit for human consumption. These additives, called denaturants, are generally either toxic (such as methanol) or have unpleasant tastes or odors (such as denatonium benzoate).

Specialty denatured alcohols are denatured alcohol formulations intended for a particular industrial use, containing denaturants chosen so as not to interfere with that use. While they are not taxed, purchasers of specialty denatured alcohols must have a government-issued permit for the particular formulation they use and must comply with other regulations.

Completely denatured alcohols are formulations that can be purchased for any legal purpose, without permit, bond, or other regulatory compliance. It is intended that it be difficult to isolate a product fit for human consumption from completely denatured alcohol. For example, the completely denatured alcohol formulation used in the United Kingdom contains (by volume) 89.66% ethanol, 9.46% methanol, 0.50% pyridine, 0.38% naphtha, and is dyed purple with methyl violet.[13]

Absolute ethanolEdit

Absolute or anhydrous alcohol generally refers to purified ethanol, containing no more than one percent water.

It is not possible to obtain absolute alcohol by simple fractional distillation, because a mixture containing around 95.6% alcohol and 4.4% water becomes a constant boiling mixture (an azeotropic mixture). 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 that distills over at 78.2 °C (351.3 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.

Currently, the most popular method of purification past 95.6% purity is desiccation using adsorbents such as starch or zeolites, which adsorb water preferentially. Azeotropic distillation and extractive distillation techniques also exist.

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

Neutralized ethanolEdit

Neutralized ethanol is used for some analytical purposes. The pH indicators are acid/base molecules that change their color requiring certain amount of acid or base. Neutralized ethanol is used in order to compensate for this error. The indicator (phenolphthalein, for example) is added to the ethanol solvent first and KOH is added until the color of the solution turns pale pink. The so obtained "neutralized ethanol" is then added to the target of the titration, which may be sample of neat organic acid. The titration stops when the same pale pink color is achieved. This way, the indicator neutralization error is eliminated.

Use Edit

As a fuelEdit

Ethanol Car

A Ford Taurus "fueled by clean burning ethanol" owned by New York City.

Main article: 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).[14] In order for ethanol to be suitable for use as a replacement to petrol in its pure form, it must be distilled to at least 70-80% purity by volume before use. For use as an additive to petrol, almost all water must be removed, otherwise it will separate from the mixture and settle to the bottom of the fuel tank, causing the fuel pump to draw water into the engine, which will cause the engine to stall.[15]

Today almost 50% of Brazilian cars are able to use 100% ethanol as fuel, that includes ethanol only engines and flex fuel engines. Flex fuel engines are able to work with all ethanol, all gasoline or any mixture of both, giving the buyer a choice for a perfect balance between price/performance issue. That was only possible due to the capability of an efficient sugar cane production. Sugar cane not only has a greater concentration of sucrose (about 30% more than corn) but is also much easier to extract. The bagasse generated by the process is not wasted and it is utilized in power plants becoming a surprisingly efficient source of 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.[16]

One method of production is through fermentation of sugar. Ethanol creates very little pollution when burned. Millions more acres of land are needed if ethanol is to be used to replace gasoline. Pure ethanol has a lower energy content than gasoline (about 30% less energy per unit volume).[17] At gas stations, ethanol is contained in a mix of ethanol and gasoline, otherwise known as gasohol. In the United States, the color yellow (symbolizing the color of corn) has become associated with the fuel and is commonly used on fuel pumps and labels.

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. [18] Growth in fuel ethanol in the United States is largely being driven by financial incentives that naturally exist when oil prices are over a certain level, as ethanol typically costs under $1.50 per gallon to manufacture (of course this is sensitive to corn prices) and is exempt from the federal gasoline tax. However, the United States RFS (renewable fuel standard) 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.[19].

Controversy Edit

As reported in "The Energy Balance of Corn Ethanol: an Update"[20], the energy returned on energy invested (EROEI) for ethanol made from corn in the U.S. is 1.34 (it yields 34 percent 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 costs more energy than it yields. [21]

Oil has historically had a much higher EROEI, especially on land in areas with pressure support, but also under the sea, which 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 used for food were converted into cornfields. It is for these reasons that ethanol alone is generally not seen as a solution to replacing conventional oil.

Politics has played a significant role in this issue. Advocates for wheat, corn and sugar growers have succeeded in their attempts to lobby for regulatory intervention encouraging adoption of ethanol, [22] stimulating debate over who the major beneficiaries of increased use of ethanol would be. Some researchers have warned [23] that ethanol produced from agricultural feedstocks will cause a global food shortage, contributing to starvation in the third world. It has also been shown that ethanol production for fuels would cease if it were not subsidized.

This has led to the development of alternative production methods that use feedstocks such as municipal waste or recycled products, rice hulls, sugarcane bagasse, small diameter trees, wood chips, and switchgrass. [24] However, these methods are in early states of research.

Blends of up to 10 per cent are normally regarded as the safe maximum for a vehicle designed to operate on petroleum. However, ethanol blends can run at up to 85 per cent or higher in specially designed flexible fueled vehicles. The volume of consumption will increase with incresing ethanol consumption.

Consumer Reports, October 2006, questions the fuel economy of a flex fuel vehicle [6]. Specifically, the report notes that fuel economy drops when an automobile uses E85, a blend of 85 per cent ethanol and 15 per cent gasoline, which follows from the lower energy content of ethanol, compared to gasoline.

In July 2007, Brazil's president said that his nation's booming ethanol business won't hurt the Amazon rain forest, dismissing criticism that the alternate fuel could cause deforestation. Environmentalists have voiced concerns that a global ethanol boom could accelerate rain forest destruction if trees are cleared to make room for crops. [25]

Rocket FuelEdit

Ethanol has been used as fuel in bipropellant rocket vehicles, in conjunction with an oxidizer. For example, the German V-2 rocket of World War 2 used ethanol fuel.

Alcoholic beverages Edit

Main article: Alcoholic beverage

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 beverages, beverages made by the action of yeast on sugary foodstuffs, or as distilled beverages, 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. Beers are made from cereal grains or other starchy materials, wines and ciders from fruit juices, and meads from honey. Cultures around the world have made fermented beverages from numerous other foodstuffs, and local and national names for various fermented beverages abound. Fermented beverages may contain up to 15–25% ethanol by volume, the upper limit being set by the yeast's tolerance for ethanol, or by the amount of sugar in the starting material.

Distilled beverages are made by distilling fermented beverages. Broad categories of distilled beverages include whiskeys, distilled from fermented cereal grains; 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 fruits, herbs, and spices into distilled spirits. A traditional example is gin, the infusion of juniper berries into neutral grain alcohol.

In a few beverages, ethanol is concentrated by means other than distillation. Applejack is traditionally made by freeze distillation: water is frozen out of fermented apple cider, leaving a more ethanol-rich liquid behind. Eisbier (most commonly, eisbock) is also freeze-distilled, with beer as the base beverage. Fortified wines 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 added to food in cooking, not only for their inherent flavors, but also because the alcohol dissolves flavor compounds that water cannot.

Chemicals derived from ethanol Edit

Ethyl esters

In the presence of an acid catalyst (typically sulfuric acid) ethanol reacts with carboxylic acids to produce ethyl esters:

CH3CH2OH + RCOOH → RCOOCH2CH3 + H2O

The two largest-volume ethyl esters are ethyl acrylate (from ethanol and acrylic acid) and ethyl acetate (from ethanol and acetic acid). Ethyl acrylate is a monomer used to prepare acrylate polymers for use in coatings and adhesives. Ethyl acetate is a common solvent used in paints, coatings, and in the pharmaceutical industry; its most familiar application in the household is as a solvent for nail polish. A variety of other ethyl esters are used in much smaller volumes as artificial fruit flavorings.

Vinegar

Vinegar is a dilute solution of acetic acid prepared by the action of Acetobacter bacteria on ethanol solutions. Although traditionally prepared from alcoholic beverages including wine, apple cider, and unhopped beer, vinegar can also be made from solutions of industrial ethanol. Vinegar made from distilled ethanol is called "distilled vinegar", and is commonly used in food pickling and as a condiment.

Ethylamines

When heated to 150–220 °C over a silica- or alumina-supported nickel catalyst, ethanol and ammonia react to produce ethylamine. Further reaction leads to diethylamine and triethylamine:

CH3CH2OH + NH3CH3CH2NH2 + H2O
CH3CH2OH + CH3CH2NH2(CH3CH2)2NH + H2O
CH3CH2OH + (CH3CH2)2NH(CH3CH2)3N + H2O

The ethylamines find use in the synthesis of pharmaceuticals, agricultural chemicals, and surfactants.

Other chemicals

Ethanol in the past has been used commercially to synthesize dozens of other high-volume chemical commodities. At the present, it has been supplanted in many applications by less costly petrochemical feedstocks. However, in markets with abundant agricultural products, but a less developed petrochemical infrastructure, such as the People's Republic of China, Pakistan, India, and Brazil, ethanol can be used to produce chemicals that would be produced from petroleum in the West, including ethylene and butadiene.

Other uses Edit

Ethanol is easily soluble in water in all proportions with a slight overall decrease in volume when the two are mixed. Absolute ethanol and 95% ethanol are themselves good solvents, somewhat less polar than water and used in perfumes, paints and tinctures. Other proportions of ethanol with water or other solvents can also be used as a solvent. Alcoholic drinks have a large variety of tastes because various flavor compounds are dissolved during brewing. When ethanol is produced as a mixing beverage it is a neutral grain spirit.

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. The peak of the disinfecting power occurs around 70% ethanol; stronger and weaker solutions of ethanol have a lessened ability to disinfect.[How to reference and link to summary or text] Solutions of this strength are often used in laboratories for disinfecting work surfaces. Ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores. Alcohol does not act like an antibiotic and is not effective against infections by ingestion. Ethanol in the low concentrations typically found in most alcoholic beverages does not have useful disinfectant or antiseptic properties, internally or externally. Ethanol is often used as an antidote in cases of methanol poisoning.

Wine with less than 16% ethanol is vulnerable to bacteria. Because of this, port is often fortified with ethanol to at least 18% ethanol by volume to halt fermentation for retaining sweetness and in preparation for aging, at which point it becomes possible to prevent the invasion of bacteria into the port, and to store the port for long whiles in wooden containers that can 'breathe', thereby permitting the port to age safely without spoiling. Because of ethanol's disinfectant property, alcoholic beverages of 18% ethanol or more by volume can be safely stored for a very long time.

Ethanol is also used in design and sketch art markers, such as Copic, and Tria.

Metabolism and toxicologyEdit

Main article: Ethanol metabolism

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. 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.

MetabolismEdit

In the human body, ethanol is first oxidized to acetaldehyde, and then to acetic acid. The first step is catalysed by the enzyme alcohol dehydrogenase, and the second by acetaldehyde dehydrogenase.

Magnitude of effectEdit

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 tolerance have a greater quantity of these enzymes, and metabolize ethanol more rapidly.

BAC (mg/dL) Symptoms[26]
50 Euphoria, talkativeness, relaxation
100 Central nervous system depression, impaired motor and sensory function, impaired cognition
>140 Decreased blood flow to brain
300 Stupefaction, possible unconsciousness
400 Possible death
>550 Expiration

The amount of ethanol in the body is typically quantified by blood alcohol content (BAC), the milligrams of ethanol per 100 milliliters 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 judgment. At higher dosages (BAC > 100mg/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.

Acetaldehyde toxicologyEdit

The initial product of ethanol metabolism, acetaldehyde, is more toxic than ethanol itself. The body can quickly detoxify some acetaldehyde by reaction with glutathione and similar thiol-containing biomolecules. When acetaldehyde is produced beyond the capacity of the body's glutathione supply to detoxify it, it accumulates in the bloodstream until further oxidized to acetic acid. The headache, nausea, and malaise associated with an alcohol hangover stem from a combination of dehydration and acetaldehyde poisoning; many health conditions associated with chronic ethanol abuse, including liver cirrhosis, alcoholism, and some forms of cancer, have been linked to acetaldehyde.[How to reference and link to summary or text] The judicial system in the United States, in a number of jurisdictions, controversially, promoted the use of disulfiram, known as Antabuse, for persons convicted of driving while (alcohol) intoxicated. Disulfiram interferes with hepatic acetaldehyde metabolism, severely exacerbating the discomforts noted above. Numerous deaths, said to be related to disulfuram use, led to the elimination of these court-based programs.[How to reference and link to summary or text]. Some medications, including paracetamol (acetaminophen), as well as exposure to organochlorides, can deplete the body's glutathione supply, enhancing both the acute and long-term risks of even moderate ethanol consumption.[How to reference and link to summary or text]. Frequent use of alcoholic beverages has also been shown to be a major contributing factor in cases of elevated blood levels of triglycerides. [3]

Bacteria-favoringEdit

Ethanol has been shown to increase the growth of Acinetobacter baumannii, a bacterium responsible for pneumonia, meningitis and urinary tract infections. This finding may contradict the common misconception that drinking alcohol could kill off a budding infection. (Smith and Snyder, 2005)

DetectionEdit

A) Preliminary Test

  • Add to 5 mL of sample (Ethyl Alcohol) 2 drops of Potassium dichromate or Potassium Permanganate and an equal amount of concentrated Sulfuric acid, then boil. Sample is positive for ethanol when the dichromate or permanganate is reduced, and the odor of acetaldehyde develops.

B) Lieben's Iodoform Test

  • Warm 3 to 5 mL of sample (Ethyl Alcohol) with 1 to 3 mL of strong solution of iodine (Lugol's Solution). Add Potassium Hydroxide solution until the color is faintly yellow. A precipitate of iodoform is formed. The other primary alcohol, aldehydes and ketones, ethyl acetate and lactic acid, also give positive results . The Iodoform crystal may be identified under the microscope appearing as hexagonal plates and stars.

C) Vitali Reaction

  • With 1 mL of sample (Ethyl Alcohol), add 3 drops of Carbon disulfide and a pellet of Potassium hydroxide in a small evaporating dish. Heat and when most of the carbon disulfide has evaporated, add 1 drop of Ammonium molybdate solution (1:10). Acidify with concentrated Sulfuric acid. Positive results gives a Violet colored solution. Acetaldehyde and Acetone react similarly and would yield the positive result.

Hazards Edit

  • Ethanol-water solutions greater than about 50% ethanol by volume are flammable (in some cases ethanol will burn at as low as a 45% solution) 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).

See also Edit


ReferencesEdit

  1. Streitweiser, Andrew Jr.; Heathcock, Clayton H.: Introduction to Organic Chemistry, Macmillan 1976, p 215
  2. 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.
  3. Lodgsdon, J.E. (1994). p. 817
  4. Ethanol Biorefinery Locations. Renewable Fuels Association.
  5. includeonly>Caroline Wyatt. "Draining France's 'wine lake'", BBC news, 10 August 2006. Retrieved on 2007-05-21.
  6. Japan Plans Its Own Green Fuel by Steve Inskeep. Morning Edition, NPR. May 15, 2007
  7. Mathewson, S.W. (1980). "Drying the Alcohol" The Manual for the Home and Farm Production of Alcohol Fuel, Ten Speed Press. URL accessed 2006-07-01.
  8. Ritter, S.K. (May 31 2004). "Biomass or Bust." Chemical & Engineering News 82(22), 31–34.
  9. Clines, Tom. "Brew Better Ethanol." Popular Science Online. July 2006. Accessed April 2007. [1]
  10. Dhinakar S. Kompala. Maximizing Ethanol Production by Engineered Pentose-Fermenting Zymononas mobilis. Department of Chemical Engineering, University of Colorado at Boulder.
  11. Providing for a Sustainable Energy Future. Bioengineering Resources, inc.
  12. Rapier, R. (June 26 2006) "E3 Biofuels: Responsible Ethanol" R-Squared Energy Blog
  13. Great Britain (2005). The Denatured Alcohol Regulations 2005. Statutory Instrument 2005 No. 1524.
  14. Reel, M. (August 19 2006) "Brazil's Road to Energy Independence" The Washington Post.
  15. http://running_on_alcohol.tripod.com/id28.html)
  16. Renewable Fuels Association Industry Statistics
  17. Rapier, R. (May 25 2006) "E85: Spinning Our Wheels" R-Squared Energy Blog
  18. First Commercial U.S. Cellulosic Ethanol Biorefinery Announced. Renewable Fuels Association.
  19. Renewable Fuel Standard Program. United States Environmental Protection Agency.
  20. Hosein Shapouri, James A. Duffield, and Michael Wang. The Energy Balance of Corn Ethanol: an Update. United States Department of Agriculture.
  21. Lang, Susan S.. Cornell ecologist's study finds that producing ethanol and biodiesel from corn and other crops is not worth the energy. Cornell University.
  22. includeonly>"U.S. seeks to boost ethanol, biodiesel", USA Today, April 10, 2007. Retrieved on 2007-05-21.
  23. includeonly>"U.N.: Not so fast with ethanol, other biofuels", MSNBC, May 8, 2007. Retrieved on 2007-05-21.
  24. Air Pollution Rules Relaxed for US Ethanol Producers. Truthout.
  25. [2]
  26. Pohorecky, L.A., and J. Brick. (1988). "Pharmacology of ethanol." Pharmacology & Therapeutics 36(3), 335-427.
  • "Alcohol." (1911). In Hugh Chisholm (Ed.) Encyclopædia Britannica, 11th ed. Online reprint
  • Lodgsdon, J.E. (1994). "Ethanol." In J.I. Kroschwitz (Ed.) Encyclopedia of Chemical Technology, 4th ed. vol. 9, pp. 812–860. New York: John Wiley & Sons.

External linksEdit



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