Ethanol facts for kids

Quick facts for kids Ethanol
Systematic name ethanol
Other names	Absolute alcohol alcohol cologne spirit drinking alcohol ethylic alcohol EtOH ethyl alcohol ethyl hydrate ethyl hydroxide ethylol grain alcohol hydroxyethane methylcarbinol
Identifiers
CAS number	64-17-5
PubChem	702
DrugBank	DB00898
ChEBI	CHEBI:16236
SMILES	CCO
InChI InChI=1/C2H6O/c1-2-3/h3H,2H2,1H3
Beilstein Reference	1718733
Gmelin Reference	787
3DMet	B01253
Properties
Molecular formula	C2H6O
Molar mass	46.06 g mol-1
Appearance	Colorless liquid
Density	0.7893 g/cm3 (at 20 °C)
Melting point	−114.14 ± 0.03 °C, Expression error: Unrecognized punctuation character "�". K, Expression error: Unrecognized punctuation character "�". °F
Boiling point	78.24 ± 0.09 °C, Expression error: Unrecognized punctuation character "�". K, Expression error: Unrecognized punctuation character "�". °F
Solubility in water	miscible
log P	−0.18
Vapor pressure	5.95 kPa (at 20 °C)
Acidity (pKa)	15.9 (H2O), 29.8 (DMSO)
Magnetic susceptibility (χ)	−33.60·10−6 cm3/mol
Refractive index (nD)	1.3611
Viscosity	1.2 mPa·s (at 20 °C), 1.074 mPa·s (at 25 °C)
Dipole moment	1.69 D
Hazards
NFPA 704	3 2 0
Flash point	14 °C (Absolute)
U.S. Permissible exposure limit (PEL)	TWA 1000 ppm (1900 mg/m3)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

A bottle of Ethanol

Ethanol, also known as marks formula, ethyl alcohol, grain alcohol or just alcohol, is a flammable, colorless chemical compound. Its chemical formula is C₂H₅OH, also written as C₂H₆O. It is the active part of alcoholic drinks, which are drunk in most cultures worldwide. It is also used as a solvent because it can dissolve many other chemicals and is not very toxic. Yeast makes most of the ethanol that people use.

Uses

Medical

Anesthetic

Ethanol is the oldest known sedative, used as an oral general anesthetic during surgery in ancient Mesopotamia and in medieval times.

Antiseptic

Ethanol is used as an antiseptic in medical wipes and hand sanitizer gels for its bactericidal and anti-fungal effects. Ethanol kills microorganisms by dissolving their membrane lipid bilayer and denaturing their proteins, and is effective against most bacteria, fungi and viruses. However, it is ineffective against bacterial spores, which can be treated with hydrogen peroxide.

Antidote

Ethanol may be administered as an antidote to ethylene glycol poisoning and methanol poisoning.

Medicinal solvent

Ethanol is used to dissolve many water-insoluble medications and related compounds. Liquid preparations of pain medications, cough and cold medicines, and mouth washes, for example, may contain up to 25% ethanol and may need to be avoided in individuals with adverse reactions to ethanol such as alcohol-induced respiratory reactions. Ethanol is present mainly as an antimicrobial preservative in over 700 liquid preparations of medicine including acetaminophen, iron supplements, ranitidine, furosemide, mannitol, phenobarbital, trimethoprim/sulfamethoxazole and over-the-counter cough medicine.

Some medicinal solutions of ethanol are also known as tinctures.

Fuel

Engine fuel

The largest single use of ethanol is as an engine fuel and fuel additive. Brazil in particular relies heavily upon the use of ethanol as an engine fuel, due in part to its role as one of the world's leading producers of ethanol. 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 gasoline-fueled cars sold in the country.

The US and many other countries primarily use E10 (10% ethanol, sometimes known as gasohol) and E85 (85% ethanol) ethanol/gasoline mixtures. Over time, it is believed that a material portion of the ≈150-billion-US-gallon (570,000,000 m³) per year market for gasoline will begin to be replaced with fuel ethanol.

USP grade ethanol for laboratory use

Australian law limits the use of pure ethanol from sugarcane waste to 10 % in automobiles. Older cars (and vintage cars designed to use a slower burning fuel) should have the engine valves upgraded or replaced.

According to an industry advocacy group, ethanol as a fuel reduces harmful tailpipe emissions of carbon monoxide, particulate matter, oxides of nitrogen, and other ozone-forming pollutants. Argonne National Laboratory analyzed greenhouse gas emissions of many different engine and fuel combinations, and found that biodiesel/petrodiesel blend (B20) showed a reduction of 8%, conventional E85 ethanol blend a reduction of 17% and cellulosic ethanol 64%, compared with pure gasoline. Ethanol has a much greater research octane number (RON) than gasoline, meaning it is less prone to pre-ignition, allowing for better ignition advance which means more torque, and efficiency in addition to the lower carbon emissions.

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 and more ground level ozone. This data has been assembled into The Clean Fuels Report comparison of fuel emissions and show that ethanol exhaust generates 2.14 times as much ozone as gasoline exhaust. When this is added into the custom Localized Pollution Index of The Clean Fuels Report, the local pollution of ethanol (pollution that contributes to smog) is rated 1.7, 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).

More than 20% of Brazilian cars are able to use 100% ethanol as fuel, which includes ethanol-only engines and flex-fuel engines. Flex-fuel engines in Brazil are able to work with all ethanol, all gasoline or any mixture of both. In the United States, 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 fleet of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugarcane.

Ethanol's high miscibility with water makes it unsuitable for shipping through modern pipelines like liquid hydrocarbons. Mechanics have seen increased cases of damage to small engines (in particular, the carburetor) and attribute the damage to the increased water retention by ethanol in fuel.

Ethanol pump station in São Paulo, Brazil

A Ford Taurus fueled by ethanol in New York City

U.S. Postal Service truck running on E85 in Minnesota

Rocket fuel

Ethanol was commonly used as fuel in early bipropellant rocket (liquid-propelled) vehicles, in conjunction with an oxidizer such as liquid oxygen. The German A-4 ballistic rocket of World War II (better known by its propaganda name V-2), which is credited as having begun the space age, used ethanol as the main constituent of B-Stoff. Under such nomenclature, the ethanol was mixed with 25% 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, which launched the first U.S. astronaut on suborbital spaceflight. Alcohols fell into general disuse as more energy-dense rocket fuels were developed, although ethanol is currently used in lightweight rocket-powered racing aircraft.

Fuel cells

Commercial fuel cells operate on reformed natural gas, hydrogen or methanol. Ethanol is an attractive alternative due to its wide availability, low cost, high purity and low toxicity. There is a wide range of fuel cell concepts that have entered trials including direct-ethanol fuel cells, auto-thermal reforming systems and thermally integrated systems. The majority of work is being conducted at a research level although there are a number of organizations at the beginning of the commercialization of ethanol fuel cells.

Household heating and cooking

Ethanol fireplaces can be used for home heating or for decoration. Ethanol can also be used as stove fuel for cooking.

Feedstock

Ethanol is an important industrial ingredient. It has widespread use as a precursor for other organic compounds such as ethyl halides, ethyl esters, diethyl ether, acetic acid, and ethyl amines.

Solvent

Ethanol is considered a universal solvent, as its molecular structure allows for the dissolving of both polar, hydrophilic and nonpolar, hydrophobic compounds. As ethanol also has a low boiling point, it is easy to remove from a solution that has been used to dissolve other compounds, making it a popular extracting agent for botanical oils.

Ethanol is found in paints, tinctures, markers, and personal care products such as mouthwashes, perfumes and deodorants. Polysaccharides precipitate from aqueous solution in the presence of alcohol, and ethanol precipitation is used for this reason in the purification of DNA and RNA.

Low-temperature liquid

Because of its low freezing point of −114 °C (−173 °F) and low toxicity, ethanol is sometimes used in laboratories (with dry ice or other coolants) as a cooling bath to keep vessels at temperatures below the freezing point of water. For the same reason, it is also used as the active fluid in alcohol thermometers.

Chemistry

Chemical formula

Ethanol is a 2-carbon alcohol. Its molecular formula is CH₃CH₂OH. The structure of the molecule of ethanol is CH
3–CH
2–OH (an ethyl group linked to a hydroxyl group), 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 group (−OH). It is a constitutional isomer of dimethyl ether. Ethanol is sometimes abbreviated as EtOH, using the common organic chemistry notation of representing the ethyl group (C₂H₅−) with Et.

Physical properties

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, such as propane.

Ethanol's adiabatic flame temperature for combustion in air is 2082 °C or 3779 °F.

Ethanol is slightly more refractive than water, having a refractive index of 1.36242 (at λ=589.3 nm and 18.35 °C or 65.03 °F). The triple point for ethanol is 150 ± 20 K.

Solvent properties

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. Its main use as a solvent is in making tincture of iodine, cough syrups, etc. It is also miscible with light aliphatic hydrocarbons, such as pentane and hexane, and with aliphatic chlorides such as trichloroethane and tetrachloroethylene.

Ethanol's miscibility with water contrasts with the immiscibility 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 alkanes 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, with up to 777 J/mol being released at 298 K.

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 and potassium hydroxides, magnesium chloride, calcium chloride, ammonium chloride, ammonium bromide, and sodium bromide. Sodium and potassium chlorides are slightly soluble in ethanol. Because the ethanol molecule also has a nonpolar end, it will also dissolve nonpolar substances, including most essential oils 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.

Azeotrope with water

At atmospheric pressure, mixtures of ethanol and water form an azeotrope at about 89.4 mol% ethanol (95.6% ethanol by mass, 97% alcohol by volume), with a boiling point of 351.3 K (78.1 °C). At lower pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures. The minimum-pressure azeotrope has an ethanol fraction of 100% and a boiling point of 306 K (33 °C), corresponding to a pressure of roughly 70 torr (9.333 kPa). Below this pressure, there is no azeotrope, and it is possible to distill absolute ethanol from an ethanol-water mixture.

Flammability

An ethanol–water solution will catch fire if heated above a temperature called its flash point and an ignition source is then applied to it. For 20% alcohol by mass (about 25% by volume), this will occur at about 25 °C (77 °F). The flash point of pure ethanol is 13 °C (55 °F), but may be influenced very slightly by atmospheric composition such as pressure and humidity. Ethanol mixtures can ignite below average room temperature. Ethanol is considered a flammable liquid (Class 3 Hazardous Material) in concentrations above 2.35% by mass (3.0% by volume; 6 proof).

Dishes using burning alcohol for culinary effects are called flambé.

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 bertam palm blossoms. Although some animal 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 anaerobiosis.

Ethanol has been detected in outer space, forming an icy coating around dust grains in interstellar clouds. Minute quantity amounts (average 196 ppb) of endogenous ethanol and acetaldehyde were found in the exhaled breath of healthy volunteers. Auto-brewery syndrome, also known as gut fermentation syndrome, is a rare medical condition in which intoxicating quantities of ethanol are produced through endogenous fermentation within the digestive system.

Images for kids

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  Infrared reflection spectra of liquid ethanol, showing the −OH band centered near 3300 cm−1 and C−H bands near 2950 cm−1

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  Near-infrared spectrum of liquid ethanol

See also

In Spanish: Etanol para niños