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Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or ...
chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be ...
. It is a simple
alcohol In , alcohol is an that carries at least one (−OH) bound to a atom. The term alcohol originally referred to the primary alcohol (ethyl alcohol), which is and is the main alcohol present in s. An important class of alcohols, of which ...

alcohol
with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ...
C2H6O. Its formula can be also written as −− or (an
ethyl group 500px, Ethyl group (highlighted blue) as part of a molecule, as the ethyl radical, and in the compounds ethanol, bromoethane, ethyl acetate">bromoethane.html" ;"title="ethanol, bromoethane">ethanol, bromoethane, ethyl acetate, and ethyl methyl eth ...

ethyl group
linked to a
hydroxyl A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...
group), and is often
abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full version of the word or phrase; for example, the word ''abbrevia ...
as EtOH. Ethanol is a volatile,
flammable , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , demonym = Germans, German , g ...
, colorless liquid with a characteristic wine-like odor and pungent taste. It is a
psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug, is a chemical substance that changes nervous system function and results in alterations in perception, mood (psychology), mood, consciousness, cognition, or beha ...
,
recreational drug Recreational drug use is the use of a psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug, is a chemical substance that changes nervous system function and results in alterations in perception, ...
, and the active ingredient in
alcoholic drink An alcoholic drink is a drink A drink (or beverage) is a liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, o ...
s. Ethanol is naturally produced by the
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...

fermentation
of
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosacc ...

sugar
s by
yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classifie ...

yeast
s or via
petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum Petroleum (), also known as crude oil and oil, is a #Latent heat of vaporization, naturally occurring, yellowish-black liquid found in geolo ...
processes such as
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...

ethylene
hydration. It has medical applications as an
antiseptic Antiseptics (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") are antimicrobial, antimicrobial substances that are applied to living biological tissue, tissue/skin to reduce the possibility of infection ...

antiseptic
and
disinfectant A disinfectant is a chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
. It is used as a
chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which ...

chemical
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
and in the
synthesis Synthesis or synthesize may also refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors **Organic synthesis, the chemical synthesis of or ...
of
organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
s. Ethanol is a fuel source.


Etymology

''Ethanol'' is the
systematic nameA systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and ...
defined by the International Union of Pure and Applied Chemistry (IUPAC) for a compound consisting of an
alkyl group In organic chemistry, an alkyl substituent A substituent is one or a group of atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space ...
with two carbon
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...

atom
s (prefix "eth-"), having a single bond between them (infix "-an-") and an attached
functional group In organic chemistry, a functional group is a substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions re ...
−OH group (suffix "-ol"). The "eth-" prefix and the qualifier "ethyl" in "ethyl alcohol" originally come from the name "ethyl" assigned in 1834 to the group − by
Justus Liebig Justus von Liebig (12 May 1803 – 18 April 1873) was a German scientist who made major contributions to agricultural and , and is considered one of the principal founders of . As a professor at the , he devised the modern laboratory-oriented ...

Justus Liebig
. He coined the word from the
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

German
name ''Aether'' of the compound −O− (commonly called "ether" in
English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become the World language, leading lan ...

English
, more specifically called "
diethyl ether Diethyl ether, or simply ether, is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

diethyl ether
"). According to the ''
Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary A historical dictionary or dictionary on historical principles is a dictionary which deals not only with the latterday meanings of words but also the historica ...
'', ''Ethyl'' is a contraction of the Ancient Greek αἰθήρ (', "upper air") and the Greek word ὕλη (', "substance"). The name ''ethanol'' was coined as a result of a resolution that was adopted at the International Conference on Chemical Nomenclature that was held in April 1892 in Geneva, Switzerland. The term "
alcohol In , alcohol is an that carries at least one (−OH) bound to a atom. The term alcohol originally referred to the primary alcohol (ethyl alcohol), which is and is the main alcohol present in s. An important class of alcohols, of which ...

alcohol
" now refers to a wider class of substances in chemistry nomenclature, but in common parlance it remains the name of ethanol. It is a medieval loan from
Arabic Arabic (, ' or , ' or ) is a Semitic language The Semitic languages are a branch of the Afroasiatic language family originating in the Middle East The Middle East is a list of transcontinental countries, transcontinental region ...

Arabic
'' al-kuḥl'', a powdered ore of antimony used since antiquity as a cosmetic, and retained that meaning in
Middle Latin Medieval Latin was the form of Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...
. The use of "alcohol" for ethanol (in full, "alcohol of wine") is modern, first recorded 1753, while before the late 18th century the term "alcohol" generally referred to any sublimated substance.


Uses


Medical


Antiseptic

Ethanol is used in medical wipes and most commonly in antibacterial
hand sanitizer Hand sanitizer (also known as hand antiseptic, hand disinfectant, hand rub, or handrub) is a liquid, gel A gel is a that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute ed system ...

hand sanitizer
gels as an
antiseptic Antiseptics (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") are antimicrobial, antimicrobial substances that are applied to living biological tissue, tissue/skin to reduce the possibility of infection ...

antiseptic
for its bactericidal and anti-fungal effects. Ethanol kills
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
s by dissolving their membrane
lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane A polarized membrane is a lipid bilayer, lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting pote ...
and
denaturing Denaturation may refer to: *Denaturation (biochemistry), a structural change in macromolecules caused by extreme conditions *Denaturation (fissile materials), transforming fissile materials so that they cannot be used in nuclear weapons *Denaturati ...
their
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s, and is effective against most
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
,
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
and
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
es. However, it is ineffective against bacterial
spores )'', growing on a thinned hybrid black poplar ''(Populus x canadensis)''. The last stage of the moss lifecycle is shown, where the sporophyte 350px, Sporophytes of moss during spring A sporophyte () is the diploid Ploidy () is the number ...
, but that can be alleviated by using
hydrogen peroxide Hydrogen peroxide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by hav ...

hydrogen peroxide
. A solution of 70% ethanol is more effective than pure ethanol because ethanol relies on water molecules for optimal antimicrobial activity. Absolute ethanol may inactivate microbes without destroying them because the alcohol is unable to fully permeate the microbe's membrane. Ethanol can also be used as a disinfectant and antiseptic because it causes cell dehydration by disrupting the osmotic balance across cell membrane, so water leaves the cell leading to cell death.


Antidote

Ethanol may be administered as an
antidote An antidote is a substance that can counteract a form of poison In biology, poisons are substances that can cause death, injury or harm to organs, tissues, cells, and DNA usually by chemical reactions or other activity on the molecular ...

antidote
to
ethylene glycol poisoning Ethylene glycol poisoning is poisoning caused by drinking ethylene glycol Ethylene glycol (IUPAC nomenclature, IUPAC name: ethane-1,2-diol) is an organic compound with the formula (CH2OH)2. It is mainly used for two purposes, as a raw material ...
and
methanol poisoning Methanol toxicity is poisoning A poison In biology, poisons are Chemical substance, substances that can cause death, injury or harm to organs, Tissue (biology), tissues, Cell (biology), cells, and DNA usually by chemical reactions or other ...
.


Medicinal solvent

Ethanol, often in high concentrations, is used to dissolve many water-insoluble medications and related compounds. Liquid preparations of
pain medications An analgesic or painkiller is any member of the group of Pharmaceutical drug, drugs used to achieve analgesia, relief from pain. They are distinct from anesthetics, which temporarily affect, and in some instances completely eliminate, sense, sensa ...
, 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 Paracetamol, also known as acetaminophen, is a medication used to treat fever and mild to moderate pain. At a standard dose, paracetamol only slightly decreases body temperature; it is inferior to ibuprofen in that respect, and the benefits of ...

acetaminophen
,
iron supplement Iron supplements, also known as iron salts and iron pills, are a number of iron formulations used to treat and prevent iron deficiency including iron deficiency anemia. For prevention they are only recommended in those with poor absorption, he ...
s,
ranitidine Ranitidine, sold under the brand name Zantac among others, is a medication used to decrease gastric acid, stomach acid production. It is commonly used in treatment of peptic ulcer disease, gastroesophageal reflux disease, and Zollinger–Ellis ...

ranitidine
,
furosemide Furosemide is a loop diuretic Loop diuretics are diuretic A diuretic () is any substance that promotes diuresis Diuresis () is increased urination Urination is the release of urine from the urinary bladder through the urethra to th ...

furosemide
,
mannitol Mannitol is a type of sugar alcohol Sugar alcohols (also called polyhydric alcohols, polyalcohols, alditols or glycitols) are organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific dis ...
,
phenobarbital Phenobarbital, also known as phenobarbitone or phenobarb, or by the trade name Luminal, is a medication of the barbiturate type. It is recommended by the World Health Organization The World Health Organization (WHO) is a list of specialized ...

phenobarbital
,
trimethoprim/sulfamethoxazole Trimethoprim/sulfamethoxazole (TMP/SMX), also known as co-trimoxazole among other names, is an antibiotic An antibiotic is a type of antimicrobial substance active against bacteria Bacteria (; common noun bacteria, singular bacterium ...
and
over-the-counter Over-the-counter (OTC) drugs are medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliat ...
cough medicine Cold medicines are a group of medications A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting ...

cough medicine
.


Pharmacology

In mammals, ethanol is primarily metabolized in the liver and stomach by
alcohol dehydrogenase Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. ...

alcohol dehydrogenase
(ADH) enzymes. These enzymes catalyze the
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

oxidation
of ethanol into
acetaldehyde Ethanal (common name acetaldehyde) is an organic chemical compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds ...
(ethanal): :CH3CH2OH + NAD+ → CH3CHO +
NADH Nicotinamide adenine dinucleotide (NAD) is a Cofactor (biochemistry), coenzyme central to metabolism. Found in all living cell (biology), cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate ...
+ H+ When present in significant concentrations, this metabolism of ethanol is additionally aided by the
cytochrome P450 Cytochromes P450 (CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are ...
enzyme
CYP2E1 Cytochrome P450 2E1 (abbreviated CYP2E1, ) is a member of the cytochrome P450 Cytochromes P450 (CYPs) are a superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classif ...
in humans, while trace amounts are also metabolized by
catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyst, catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in prote ...

catalase
. The resulting intermediate, acetaldehyde, is a known carcinogen, and poses significantly greater toxicity in humans than ethanol itself. Many of the symptoms typically associated with alcohol intoxication — as well as many of the health hazards typically associated with the long-term consumption of ethanol — can be attributed to acetaldehyde toxicity in humans. The subsequent oxidation of acetaldehyde into acetate is performed by
aldehyde dehydrogenase Aldehyde dehydrogenases () are a group of enzymes that catalyse the oxidation of aldehydes. They convert aldehydes (R–C(=O)) to carboxylic acids (R–C(=O)). The oxygen comes from a water molecule. To date, nineteen ALDH genes have bee ...
(ALDH) enzymes. A mutation in the ALDH2 gene that encodes for an inactive or dysfunctional form of this enzyme affects roughly 50% of east Asian populations, contributing to the characteristic
alcohol flush reaction Alcohol flush reaction is a condition in which a person develops flushes or blotches associated with erythema on the face, neck, shoulders, and in some cases, the entire body after consuming alcoholic beverages. The reaction is the result of an ac ...
that can cause temporary reddening of the skin as well as a number of related, and often unpleasant, symptoms of acetaldehyde toxicity. This mutation is typically accompanied by another mutation in the
alcohol dehydrogenase Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. ...

alcohol dehydrogenase
enzyme
ADH1B Alcohol dehydrogenase 1B is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, an ...
in roughly 80% of east Asians, which improves the catalytic efficiency of converting ethanol into acetaldehyde.


Recreational

As a
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
depressant A depressant, or central depressant, is a drug that lowers neurotransmission levels, which is to depress or reduce arousal or stimulation, in various areas of the brain. Depressants are also occasionally referred to as "downers" as they lower t ...
, ethanol is one of the most commonly consumed
psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug, is a chemical substance that changes nervous system function and results in alterations in perception, mood (psychology), mood, consciousness, cognition, or beha ...
s. Despite alcohol's psychoactive properties, it is readily available and legal for sale in most countries. However, there are laws regulating the sale, exportation/importation, taxation, manufacturing, consumption, and possession of alcoholic beverages. The most common regulation is prohibition for minors.


Fuel


Engine fuel

The largest single use of ethanol is as an engine
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical con ...

fuel
and
fuel additive Petrol additives increase petrol's octane rating or act as corrosion inhibitors or lubricants, thus allowing the use of higher compression ratios for greater efficiency and power. Types of additives include metal deactivators, corrosion inhibitors, ...
.
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At 8.5 million square kilometers (3.2 million square miles) and with over 211 mill ...

Brazil
in particular relies heavily upon the use of ethanol as an engine fuel, due in part to its role as one of the globe's leading producers of ethanol.
Gasoline Gasoline () or petrol () (see the #Etymology, etymology for naming differences and the use of the term ''gas'') is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignition engine, spark-ignite ...

Gasoline
sold in Brazil contains at least 25%
anhydrous A substance is anhydrous if it contains no water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the flui ...
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. Brazilian ethanol is produced from
sugar cane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall w ...

sugar cane
, which has relatively high yields (830% more fuel than the fossil fuels used to produce it) compared to some other energy crops. The US and many other countries primarily use E10 (10% ethanol, sometimes known as gasohol) and E85 (85% ethanol) ethanol/gasoline mixtures. 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 Advocacy groups, also known as special interest groups, use various forms of advocacy Advocacy is an activity by an individual or group that aims to influence decisions within political, economic, and social institutions. Advocacy include ...
, ethanol as a fuel reduces harmful
tailpipe emissions An exhaust system is used to guide reaction exhaust gas Exhaust gas or flue gas Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler Pola ...
of carbon monoxide, particulate matter,
oxides of nitrogenNitrogen oxide may refer to a binary compound of oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly ...
, and other ozone-forming pollutants.
Argonne National Laboratory Argonne National Laboratory is a science and engineering research United States Department of Energy National Labs, national laboratory operated by University of Chicago, UChicago Argonne LLC for the United States Department of Energy. The facil ...
analyzed greenhouse gas emissions of many different engine and fuel combinations, and found that
biodiesel Biodiesel is a form of diesel fuel Diesel fuel in general is any liquid fuel Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy In physical sciences Physical science is a ...

biodiesel
/petrodiesel blend ( B20) showed a reduction of 8%, conventional
E85 Logo used in the United States for E85 fuel E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel Ethanol fuel is ethyl alcohol, the same type of alcohol File:Alcohol general.svg, upright=0.8, The bond ...
ethanol blend a reduction of 17% and
cellulosic ethanol Cellulosic ethanol is (ethyl alcohol) produced from (the stringy fiber of a plant) rather than from the plant's s or . It can be produced from es, , , or other plants. It is generally discussed for use as a . The that plants offsets some of the ...
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 Formaldehyde ( , also ) (systematic nameA systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance A chemical substance is a form of matter In classical physics and general chemist ...
and related species such as acetaldehyde. This leads to a significantly larger photochemical reactivity and more
ground level ozones over the period 1979 to 2000. In June to August, photochemical ozone production causes very high concentrations over the East Coast of the US and China. Ozone Ozone (), or trioxygen, is an inorganic molecule File:Pentacene on Ni(111) STM.jp ...
. 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 gasoline exhaust. When this is added into the custom ''Localized Pollution Index (LPI)'' 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 The California Air Resources Board (CARB or ARB) is the "clean air agency" in the government of California. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor ...
formalized this issue in 2008 by recognizing control standards for formaldehydes as an emissions control group, much like the conventional
NOx In atmospheric chemistry Atmospheric chemistry is a branch of in which the of the and that of other planets is studied. It is a of research and draws on , , , , , and and other disciplines. Research is increasingly connected with other a ...

NOx
and Reactive Organic Gases (ROGs). World production of ethanol in 2006 was , 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 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 fleet of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown
sugar cane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall w ...

sugar cane
.
Sugar cane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall w ...

Sugar cane
not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The
bagasse Bagasse ( ) is the dry pulpy fibrous material that remains after crushing sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, perennial A perennial plant or simply perennial is a plant that lives more than two yea ...
generated by the process is not wasted, but is used in power plants to produce electricity. In the United States, the ethanol fuel industry is based largely on
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of the Americas, indige ...

corn
. According to the Renewable Fuels Association, as of 30 October 2007, 131 grain ethanol bio-refineries in the United States have the capacity to produce of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add of new capacity in the next 18 months. Over time, it is believed that a material portion of the ≈ per year market for gasoline will begin to be replaced with fuel ethanol.
Sweet sorghum Sweet sorghum is any of the many varieties of the sorghum ''Sorghum'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles tha ...
is another potential source of ethanol, and is suitable for growing in dryland conditions. The
International Crops Research Institute for the Semi-Arid Tropics The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) is an international organization which conducts agricultural research for rural development, headquartered in Patancheru Patancheru is a located in north western end ...
( ICRISAT) is investigating the possibility of growing sorghum as a source of fuel, food, and animal feed in arid parts of
Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere, Eastern and Northern Hemisphere, Northern Hemisphere of the Earth, Hemispheres. It shares the continental landmass of Eurasia with the cont ...

Asia
and
Africa Africa is the world's second-largest and second-most populous continent A continent is any of several large landmass A landmass, or land mass, is a large region In geography Geography (from Greek: , ''geographia'', ...

Africa
.
Sweet sorghum Sweet sorghum is any of the many varieties of the sorghum ''Sorghum'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles tha ...
has one-third the water requirement of sugarcane over the same time period. It also requires about 22% less water than corn (also known as maize). The world's first sweet sorghum ethanol distillery began commercial production in 2007 in Andhra Pradesh, India. Ethanol's high
miscibility Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. ...
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 A carburetor (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American En ...

carburetor
) and attribute the damage to the increased water retention by ethanol in fuel.


Rocket fuel

Ethanol was commonly used as fuel in early
bipropellant The highest specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket engine, rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is ...
rocket A rocket (from it, rocchetto, , bobbin/spool) is a spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite alt=, A full-size model of the Earth observation satellite ERS 2 ...

rocket
(liquid-propelled) vehicles, in conjunction with an
oxidizer An oxidizing agent, also known as an oxidant or oxidizer, is a substance that has the ability to oxidize other substances — in other words to electron acceptor, accept their electrons. Common oxidizing agents are oxygen, hydrogen peroxi ...
such as liquid oxygen. The German A-4 ballistic rocket of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
, better known by its propaganda name
V-2 #REDIRECT V-2 rocket#REDIRECT V-2 rocket The V-2 (german: Vergeltungswaffe 2, "Retribution Weapon 2"), with the technical name '' Aggregat 4'' (A4), was the world's first long-range guided ballistic missile. The missile, powered by a liquid-p ...

V-2
, which is credited as having begun the space age, used ethanol as the main constituent of . Under such nomenclature, the ethanol was mixed with 25% water to reduce the combustion chamber temperature.Braeunig, Robert A
"Rocket Propellants."
(Website). Rocket & Space Technology, 2006. Retrieved 23 August 2007.
The V-2's design team helped develop U.S. rockets following World War II, including the ethanol-fueled
Redstone rocket The PGM-11 Redstone was the first large American ballistic missile. A short-range ballistic missile (SRBM), it was in active service with the United States Army in West Germany from June 1958 to June 1964 as part of NATO's Cold War defense of We ...
which launched the first U.S. satellite. Alcohols fell into general disuse as more energy-dense rocket fuels were developed, although ethanol is currently used in
lightweight Lightweight is a weight class in combat sports and rowing (sport), rowing. Boxing Professional boxing The lightweight division is over 130 pounds (59 kilograms) and up to 135 pounds (61.2 kilograms) boxing weight classes, weight class in the sp ...

lightweight
rocket-powered racing aircraft.


Fuel cells

Commercial fuel cells operate on reformed natural gas,
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
or
methanol Methanol, also known as methyl alcohol, amongst other names, is a chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. ...

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
halide A halide is a binary phase, of which one part is a halogen atom and the other part is an chemical element, element or radical (chemistry), radical that is less electronegative (or more electropositive) than the halogen, to make a, e.g., fluoride, ...
s, ethyl
ester An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...

ester
s, diethyl ether, acetic acid, and ethyl
amine In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

amine
s.


Solvent

Ethanol is considered a universal
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
, as its
molecular A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

molecular
structure allows for the dissolving of both
polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the clim ...
,
hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...

hydrophilic
and
nonpolar In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
,
hydrophobic In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence ...
compounds. As ethanol also has a low
boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating the alcohol, the vapors fill in the space, inc ...
, 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.
Cannabis ''Cannabis'' () is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

Cannabis
oil extraction methods often use ethanol as an extraction
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
, and also as a post-processing solvent to remove oils, waxes, and
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally ...

chlorophyll
from solution in a process known as winterization. Ethanol is found in
paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned wi ...

paint
s,
tincture A tincture is typically an extract An extract is a substance made by extracting a part of a raw material A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce go ...
s, markers, and personal care products such as mouthwashes, perfumes and deodorants. However,
polysaccharides , a beta-glucan polysaccharide Image:amylose 3Dprojection.svg, 350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the o ...
precipitate In aqueous solution, precipitation is the process of transforming a dissolved substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a de ...
from aqueous solution in the presence of alcohol, and ethanol precipitation is used for this reason in the purification of
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
and
RNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Re ...

RNA
.


Low-temperature liquid

Because of its low freezing point -173.20 °F (−114.14 °C) and low toxicity, ethanol is sometimes used in laboratories (with
dry ice Dry ice is the solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is chara ...

dry ice
or other coolants) as a
cooling bath A cooling bath, in laboratory chemistry practice, is a liquid mixture which is used to maintain low temperatures, typically between 13 °C and −196 °C. These low temperatures are used to collect liquids after distillation Distilla ...
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 thermometer The alcohol thermometer or spirit thermometer is an alternative to the mercury-in-glass thermometer and has similar functions. Unlike the mercury-in-glass thermometer, the contents of an alcohol thermometer are less toxic and will evaporate quickl ...

alcohol thermometer
s.


Chemistry


Chemical formula

Ethanol is a 2-carbon alcohol. Its chemical formula, molecular formula is CH3CH2OH. 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 sometimes abbreviated as EtOH, using the common organic chemistry notation of representing the ethyl group (C2H5−) with Et.


Physical properties

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 is slightly more refractive than water, having a refractive index of 1.36242 (at λ=589.3 nm and ). The triple point for ethanol is at a pressure of .


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 Diethyl ether, or simply ether, is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

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 1,1,1-Trichloroethane, 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. Mixtures of ethanol and water form an azeotrope at about 89 mole-% ethanol and 11 mole-% water or a mixture of 95.6 percent ethanol by mass (or about 97% alcohol by volume) at normal pressure, which boils at 351K (78 °C). This azeotropic composition is strongly temperature- and pressure-dependent and vanishes at temperatures below 303 K. 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 hydroxides, magnesium chloride, calcium chloride, ammonium chloride, ammonium bromide, and sodium bromide. Sodium chloride, 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''Merck Index of Chemicals and Drugs'', 9th ed.; monographs 6575 through 6669 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.


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 . The flash point of pure ethanol is , 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 Alcohol proof, proof). : Dishes using burning alcohol for culinary effects are called flambé.


Natural occurrence

Ethanol is a byproduct of the Metabolism, 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 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 parts per billion, 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 Alcohol intoxication, intoxicating quantities of ethanol are produced through endogenous
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...

fermentation
within the digestive system.


Production

Ethanol is produced both as a petrochemical, through the hydration of ethylene and, via biological processes, by fermentation (biochemistry), fermenting sugars with
yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classifie ...

yeast
. Which process is more economical depends on prevailing prices of petroleum and grain feed stocks. In the 1970s most industrial ethanol in the United States was made as a petrochemical, but in the 1980s the United States introduced subsidies for corn-based ethanol and today it is almost all made from that source. In India ethanol is made from sugarcane.


Ethylene hydration

Ethanol for use as an industrial feedstock or solvent (sometimes referred to as synthetic ethanol) is made from petrochemical feed stocks, primarily by the acid-catalysis, catalyzed hydration of
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...

ethylene
: : ethylene, + → 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 in the presence of high pressure steam at where a 5:3 ethylene to steam ratio is maintained. This process was used on an industrial scale by Union Carbide, Union Carbide Corporation and others in the U.S., 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 hydrolysis, hydrolyzed to yield ethanol and regenerate the sulfuric acid: : + sulfuric acid, → ethyl sulfate, H : ethyl sulfate, H + H2O, → H + sulfuric acid,


From CO2

Ethanol has been produced in the laboratory by converting carbon dioxide via biological and electrochemical reactions. : CO2 + → H + side products


Fermentation

Ethanol in alcoholic beverages and fuel is produced by fermentation. Certain species of
yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classifie ...

yeast
(e.g., ''Saccharomyces cerevisiae'') metabolism, metabolize polysaccharide, sugar, producing ethanol and carbon dioxide. The chemical equations below summarize the conversion: : glucose, → 2 H + 2 CO2 : sucrose, + → 4 H + 4 CO2 Fermentation is the process of culturing yeast under favorable thermal conditions to produce alcohol. This process is carried out at around . Toxicity of ethanol to yeast limits the ethanol concentration obtainable by brewing; higher concentrations, therefore, are obtained by Fortified wine, fortification or distillation. The most ethanol-tolerant yeast strains can survive up to approximately 18% ethanol by volume. To produce ethanol from starchy materials such as cereals, 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.


Cellulose

Sugars for ethanol fermentation can be obtained from cellulose. Deployment of this technology could turn a number of cellulose-containing agricultural by-products, such as corncobs, straw, and sawdust, into renewable energy resources. Other agricultural residues such as sugar cane bagasse and energy crops such as switchgrass may also be fermentable sugar sources.


Testing

Breweries and biofuel plants employ two methods for measuring ethanol concentration. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the C−H band at 2900 cm−1. This method uses a relatively inexpensive solid-state sensor that compares the C−H 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


Distillation

Ethylene hydration or brewing produces an ethanol–water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation at atmospheric pressure can concentrate ethanol to 95.6% by weight (89.5 mole%). This mixture is an azeotrope with a boiling point of , and ''cannot'' be further purified by distillation. Addition of an entraining agent, such as benzene, cyclohexane, or heptane, allows a new ternary azeotrope comprising the ethanol, water, and the entraining agent to be formed. This lower-boiling ternary azeotrope is removed preferentially, leading to water-free ethanol.


Molecular sieves and desiccants

Apart from distillation, ethanol may be dried by addition of a desiccant, such as molecular sieves, cellulose, or cornmeal. The desiccants can be dried and reused. Molecular sieves can be used to selectively absorb the water from the 95.6% ethanol solution. Molecular sieves of pore-size 3 Ångstrom, a type of zeolite, effectively sequester water molecules while excluding ethanol molecules. Heating the wet sieves drives out the water, allowing regeneration of their dessicant capability.


Membranes and reverse osmosis

Membranes can also be used to separate ethanol and water. Membrane-based separations are not subject to the limitations of the water-ethanol azeotrope because the separations are 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 the 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.


Other techniques

A variety of other techniques have been discussed, including the following: * Salting using potassium carbonate to exploit its insolubility will cause a phase separation with ethanol and water. This offers a very small potassium carbonate impurity to the alcohol that can be removed by distillation. This method is very useful in purification of ethanol by distillation, as ethanol forms an azeotrope with water. * Direct electrochemical reduction of carbon dioxide to ethanol under ambient conditions using copper nanoparticles on a carbon nanospike film as the catalyst; * Extraction of ethanol from grain mash by supercritical carbon dioxide; * Pervaporation; * Fractional freezing is also used to concentrate fermented alcoholic solutions, such as traditionally made Applejack (beverage); * Pressure swing adsorption.


Grades of ethanol


Denatured alcohol

Pure ethanol and alcoholic beverages are heavily Sin tax, taxed as psychoactive drugs, but ethanol has many uses that do not involve its consumption. 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 Methanol, also known as methyl alcohol, amongst other names, is a chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. ...

methanol
, naphtha, and pyridine. Products of this kind are called ''denatured alcohol.''


Absolute alcohol

Absolute or anhydrous alcohol refers to ethanol with a low water content. There are various grades with maximum water contents ranging from 1% to a few parts per million (ppm) levels. If azeotropic distillation is used to remove water, it will contain trace amounts of the material separation agent (e.g. benzene). Absolute alcohol is not intended for human consumption. 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 U.S., equivalent to 175 degrees proof in the UK system.


Rectified spirits

Rectified spirit, an azeotropic composition of 96% ethanol containing 4% water, is used instead of anhydrous ethanol for various purposes. Spirits of wine are about 94% ethanol (188 proof (alcohol), proof). The impurities are different from those in 95% (190 proof) laboratory ethanol.


Reactions

Ethanol is classified as a primary alcohol, meaning that the carbon that 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 acids to produce ethyl
ester An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...

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 used as a diuretic.


Dehydration

In the presence of acid catalysts, ethanol converts to
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...

ethylene
. Typically solid acids such as silica are used: :   CH3CH2OH → H2C=CH2 + H2O Ethylene produced from sugar-derived ethanol (primarily in Brazil) competes with ethylene produced from petrochemical feedstocks such as naphtha and ethane. Under alternative conditions,
diethyl ether Diethyl ether, or simply ether, is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

diethyl ether
results: :2 CH3CH2OH → CH3CH2OCH2CH3 + H2O


Combustion

Complete combustion of ethanol forms carbon dioxide and water: :C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (l); −ΔHc = 1371 kJ/mol = 29.8 kJ/g = 327 kcal/mol = 7.1 kcal/g :C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g); −ΔHc = 1236 kJ/mol = 26.8 kJ/g = 295.4 kcal/mol = 6.41 kcal/g 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 acidities 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 equilibrium that is closely balanced: :CH3CH2OH + NaOH CH3CH2ONa + H2O


Halogenation

Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are illustrative. Ethanol reacts with hydrogen halides 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, which forms chloral hydrate upon reaction with water: :4 Cl2 + CH3CH2OH → CCl3CHO + 5 HCl :CCl3CHO + H2O → CCl3C(OH)2H


Oxidation

Ethanol can be oxidized to
acetaldehyde Ethanal (common name acetaldehyde) is an organic chemical compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds ...
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.


Metabolism

Ethanol is similar to macronutrients such as proteins, fats, and carbohydrates in that it provides calories. When consumed and metabolized, it contributes 7 calories per gram via ethanol metabolism.


Safety

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 limits.


History

The ethanol fermentation, fermentation of sugar into ethanol is one of the earliest biotechnology, biotechnologies employed by humans. Ethanol has historically been identified variously as spirit of wine or ardent spirits, and as aqua vitae or aqua vita. The intoxicating effects of its consumption have been known since ancient times. Ethanol has been used by humans since prehistory as the intoxicating ingredient of alcoholic beverages. Dried residue on 9,000-year-old pottery found in China suggests that Neolithic people consumed alcoholic beverages. The inflammable nature of the exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus (c. 371–287 BCE), and Pliny the Elder (23/24–79 CE). However, this did not immediately lead to the isolation of ethanol, even despite the development of more advanced distillation techniques in second- and third-century Roman Egypt. An important recognition, first found in one of the writings attributed to Jabir ibn Hayyan, Jābir ibn Ḥayyān (ninth century CE), was that by Salt-effect distillation, adding salt to boiling wine, which increases the wine's relative volatility, the flammability of the resulting vapors may be enhanced. The distillation of wine is attested in Arabic works attributed to Al-Kindi, al-Kindī (c. 801–873 CE) and to Al-Farabi, al-Fārābī (c. 872–950), and in the 28th book of Al-Zahrawi, al-Zahrāwī's (Latin: Abulcasis, 936–1013) ''Kitāb al-Taṣrīf'' (later translated into Latin as ''Liber servatoris''). In the twelfth century, recipes for the production of ''aqua ardens'' ("burning water", i.e., ethanol) by distilling wine with salt started to appear in a number of Latin works, and by the end of the thirteenth century it had become a widely known substance among Western European chemists. The works of Taddeo Alderotti (1223–1296) describe a method for concentrating ethanol involving repeated fractional distillation through a water-cooled still, by which an ethanol purity of 90% could be obtained. The medicinal properties of ethanol were studied by Arnald of Villanova (1240–1311 CE) and John of Rupescissa (c. 1310–1366), the latter of whom regarded it as a life-preserving substance able to prevent all diseases (the ''aqua vitae'' or "water of life", also called by John the ''Aether (classical element), quintessence'' of wine). In China, archaeological evidence indicates that the true distillation of alcohol began during the 12th century Jin dynasty (1115–1234), Jin or Southern Song dynasty, Southern Song dynasties. A still has been found at an archaeological site in Qinglong, Hebei, dating to the 12th century. In India, the true distillation of alcohol was introduced from the Middle East, and was in wide use in the Delhi Sultanate by the 14th century. In 1796, German-Russian chemist Johann Tobias Lowitz obtained pure ethanol by mixing partially purified ethanol (the alcohol-water azeotrope) with an excess of anhydrous alkali and then distilling the mixture over low heat. French chemist Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1807 Nicolas-Théodore de Saussure determined ethanol's chemical formula. Fifty years later, Archibald Scott Couper published the structural formula of ethanol. It was one of the first structural formulas determined. Ethanol was first prepared synthetically in 1825 by Michael Faraday. He found that sulfuric acid could absorb large volumes of coal gas. He gave the resulting solution to Henry Hennell, a British chemist, who found in 1826 that it contained "sulphovinic acid" (Ethyl sulfate, ethyl hydrogen sulfate). In 1828, Hennell and the French chemist Georges-Simon Serullas independently discovered that sulphovinic acid could be decomposed into ethanol. On page 368, Hennell produces ethanol from "sulfovinic acid" (Ethyl sulfate, ethyl hydrogen sulfate). Thus, in 1825 Faraday had unwittingly discovered that ethanol could be produced from
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...

ethylene
(a component of coal gas) by Acid catalysis, acid-catalyzed hydration, a process similar to current industrial ethanol synthesis.In 1855, the French chemist Marcellin Berthelot confirmed Faraday's discovery by preparing ethanol from pure ethylene. (Note: The chemical formulas in Berthelot's paper are wrong because chemists at that time used the wrong atomic masses for the elements; e.g., carbon (6 instead of 12), oxygen (8 instead of 16), etc.) 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. Use as an automotive fuel dates back to 1908, with the Ford Model T able to run on petrol (gasoline) or ethanol. It fuels some spirit lamps. Ethanol intended for industrial use is often produced from
ethylene Ethylene (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science C ...

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 a 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 engines.


See also

* 1-Propanol * Butanol fuel * Ethanol-induced non-lamellar phases in phospholipids * Vinyl alcohol, Ethenol * Ethynol * Isopropyl alcohol * Methanol * Rubbing alcohol * tert-Butyl alcohol * Timeline of alcohol fuel


References


Further reading

* . * * *


External links


Alcohol (Ethanol)
at ''The Periodic Table of Videos'' (University of Nottingham)
International Labour Organization
ethanol safety information



* [http://webbook.nist.gov/cgi/cbook.cgi?Name=ethanol&Units=SI National Institute of Standards and Technology] chemical data on ethanol
Chicago Board of Trade
news and market data on ethanol futures * Calculation o
vapor pressureliquid densitydynamic liquid viscositysurface tension
of ethanol
Ethanol History
A look into the history of ethanol


Industrial ethanol production process flow diagram using ethylene and sulphuric acid
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