·
Linear Formula CH3CH2OH
·
Molecular Weight 46.07
·
Beilstein Registry
Number 1718733
Ethanol /ˈɛθənɒl/, also commonly called ethyl
alcohol, drinking alcohol, or simply alcohol
is the principal type of alcohol found in alcoholic
beverages, produced by the fermentation
of sugars
by yeasts.
It is a neurotoxic[14][15]
psychoactive drug and one of the oldest recreational
drugs used by humans. It can cause alcohol
intoxication when consumed in
sufficient quantity.
Detailed description
Ethanol
is a volatile, flammable,
colorless liquid with a slight chemical odor. It is used as an antiseptic,
a solvent,
a fuel, and, due to its low freezing
point, the active fluid in post-mercury thermometers.
Its structural formula, CH3CH
2OH, is often abbreviated as C
2H
5OH, C
2H
6O or EtOH.
Etymology
Ethanol is the systematic
name defined by the International Union of Pure and
Applied Chemistry (IUPAC) for a molecule with two carbon
atoms (prefix "eth-"), having a single bond between them (suffix
"-ane"), and an attached functional
group-OH group (suffix "-ol").[1]The prefix ethyl was coined in 1834 by the German chemist Justus Liebig.[16] Ethyl is a contraction of the French word ether (any substance that evaporated or sublimated readily at room temperature) and the Greek word ύλη (hyle, substance).[17]
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.[18]
The term "alcohol" now refers to a wider class of substances in chemistry nomenclature, but in common parlance it remains the name of ethanol. Ultimately a medieval loan from Arabic al-kuḥl,[19] use of alcohol in this sense is modern, introduced in the mid 18th century. Before that time, Middle Latin alcohol referred to "powdered ore of antimony; powdered cosmetic", by the later 17th century "any sublimated substance; distilled spirit" use for "the spirit of wine" (shortened from a full expression alcohol of wine) recorded 1753. The systematic use in chemistry dates to 1850.
Chemical formula
Ethanol
is a 2-carbon alcohol. Its 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
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.
Uses
Medical
Antiseptic
Ethanol
is used in medical wipes and in most common antibacterial hand
sanitizer gels at a concentration of about 62% v/v as an antiseptic.
Ethanol kills organisms by denaturing
their proteins
and dissolving their lipids and is effective against most bacteria
and fungi,
and many viruses,
but is ineffective against bacterial spores.[20]
Antitussive
Ethanol
is also widely used, clinically and over the counter, as an antitussive
agent.[21]
Antidote
Ethanol
may be administered as an antidote
to methanol
poisoning.[22]
Medicinal solvent
Ethanol,
often in surprisingly high concentrations, is used to dissolve many
water-insoluble medications and related compounds. Proprietary liquid
preparations of cough and cold remedies, analgesics, and mouth washes may be
dissolved in 1 to 25% concentrations of ethanol and may need to be avoided in
individuals with adverse reactions to ethanol such as alcohol-induced respiratory
reactions.[23]
Recreational
Ethanol
is a central nervous system depressant
and has significant psychoactive effects in sublethal doses. Based on its
abilities to alter human consciousness,
ethanol is considered a psychoactive
drug.[24]The amount of ethanol in the body is typically quantified by blood alcohol content (BAC), which is here taken as weight of ethanol per unit volume of blood. Small doses of ethanol, in general, produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. At higher dosages (BAC > 1 g/L), ethanol acts as a central nervous system depressant, producing at progressively higher dosages, impaired sensory and motor function, slowed cognition, stupefaction, unconsciousness, and possible death. Ethanol is commonly consumed as a recreational drug, especially while socializing, due to its psychoactive effects.
Fuel
Engine fuel
|
Fuel type
|
MJ/L
|
MJ/kg
|
|
|
~19.5
|
|||
|
17.9
|
19.9
|
||
|
E85
(85% ethanol, 15% gasoline) |
25.2
|
33.2
|
105
|
|
25.3
|
~55
|
||
|
26.8
|
50.
|
||
|
Aviation
gasoline
(high-octane gasoline, not jet fuel) |
33.5
|
46.8
|
100/130 (lean/rich)
|
|
Gasohol
(90% gasoline + 10% ethanol) |
33.7
|
47.1
|
93/94
|
|
Regular gasoline/petrol
|
34.8
|
min. 91
|
|
|
Premium gasoline/petrol
|
max. 104
|
||
|
38.6
|
45.4
|
25
|
|
|
Charcoal, extruded
|
50
|
23
|
|
Ethanol may also be utilized as a rocket fuel, and is currently in lightweight rocket-powered racing aircraft.[31]
Australian law limits the use of pure ethanol sourced from sugarcane waste to up to 10% in automobiles. It has been recommended that older cars (and vintage cars designed to use a slower burning fuel) have their valves upgraded or replaced.[32]
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.[33] Argonne National Laboratory analyzed the greenhouse gas emissions of many different engine and fuel combinations. Comparing ethanol blends with gasoline alone, they showed reductions of 8% with the biodiesel/petrodiesel blend known as B20, 17% with the conventional E85 ethanol blend, and that using cellulosic ethanol lowers emissions 64%.[34]
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.[35] This leads to a significantly larger photochemical reactivity that generates much more ground level ozone.[36] These data have been assembled into The Clean Fuels Report comparison of fuel emissions[37] and show that ethanol exhaust generates 2.14 times as much ozone as does gasoline exhaust.[citation needed] When this is added into the custom Localised Pollution Index (LPI) of The Clean Fuels Report the local pollution (pollution that contributes to smog) is 1.7 on a scale where gasoline is 1.0 and higher numbers signify greater pollution.[citation needed] 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).[38]
World production of ethanol in 2006 was 51 gigalitres (1.3×1010 US gal), with 69% of the world supply coming from Brazil and the United States.[39] More than 20% of Brazilian cars are able to use 100% ethanol as fuel, which includes ethanol-only engines and flex-fuel engines.[40] Flex-fuel engines in Brazil are able to work with all ethanol, all gasoline or any mixture of both. In the US flex-fuel vehicles can run on 0% to 85% ethanol (15% gasoline) since higher ethanol blends are not yet allowed or efficient. Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugar cane. Sugar cane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The bagasse generated by the process is not wasted, but is used in power plants to produce electricity.[citation needed]
The United States fuel ethanol industry is based largely on 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 7.0 billion US gallons (26,000,000 m3) of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add 6.4 billion US gallons (24,000,000 m3) of new capacity in the next 18 months. 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.[41]
Sweet sorghum is a potential source of ethanol, which is suitable for growing in dryland conditions. It is being investigated by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) for its potential to provide fuel, along with food and animal feed, in arid parts of Asia and Africa.[42] The water requirement of sweet sorghum is one-third that of sugarcane on a comparable time scale. Also, sweet sorghum requires about 22% less water than corn also known as maize. The world’s first sweet sorghum-based ethanol production distillery began commercial ethanol production in 2007 in Andhra Pradesh, India.[43]
Ethanol's high miscibility with water means that it cannot be shipped through modern pipelines like liquid hydrocarbons.[44] Mechanics have seen increased cases of damage to small engines, in particular, the carburetor, attributable to the increased water retention by ethanol in fuel.[45]
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 V-2
rocket of World War II, credited
with beginning the space age, used ethanol, mixed with 25% of water to reduce
the combustion chamber temperature.[46][47]
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. satellite.[48]
Alcohols fell into general disuse as more efficient rocket fuels were
developed.[47]
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 are a wide range of fuel cell concepts that
have been trialled 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 commercialization of ethanol fuel cells.[49]
Household heating
Ethanol
fuels flue-less, real flame fireplaces. Ethanol is kept in a burner containing
a wick such as glass wool, a safety shield to reduce the chances of accidents
and an extinguisher such as a plate or shutter to cut off oxygen.It provides almost the same visual benefits of a real flame log or coal fire without the need to vent the fumes via a flue as ethanol produces very little hazardous carbon monoxide, and little or no noticeable scent. It does emit carbon dioxide and requires oxygen. Therefore, external ventilation of the room containing the fire is needed to ensure safe operation.
An additional benefit is that, unlike a flue based fireplace, 100% of the heat energy produced enters the room. This serves to offset some of the heat loss from an external air vent, as well as offset the relatively high cost of the fuel compared to other forms of heating.
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 miscible
with water and is a good general purpose solvent.
It is found in paints, tinctures,
markers, and personal care products such as mouthwashes, perfumes and
deodorants. However, 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.
Adverse effects
Loss of balance
When
alcohol reaches the brain, it has the ability to delay signals that are sent
between nerve cells that control balance, thinking and movement.[50]
Gastrointestinal diseases
Alcohol
stimulates gastric juice production, even when food is not present. In other
words, when a person drinks alcohol, the alcohol will stimulate stomach's
acidic secretions that are intended to digest protein molecules. Consequently,
the acidity has potential to harm the inner lining of the stomach. Normally,
the stomach lining is protected by a mucus layer that prevents any acids from
reaching the stomach cells.However, in patients who have a peptic ulcer disease (PUD), this mucus layer is broken down. PUD is commonly associated with a bacteria H. pylori. H. pylori secretes a toxin that weakens the mucosal wall. As a result, acid and protein enzymes penetrate the weakened barrier. Because alcohol stimulates a person's stomach to secrete acid, a person with PUD should avoid drinking alcohol on an empty stomach. Drinking alcohol would cause more acid release to damage the weakened stomach wall.[51] Complications of this disease could include a burning pain in the abdomen, bloating and in severe cases, the presence of dark black stools indicate internal bleeding.[52] A person who drinks alcohol regularly is strongly advised to reduce their intake to prevent PUD aggravation.[52]
Short-term toxic allergy-like
responses
Ethanol-containing
beverages can cause urticarial skin
eruptions, systemic dermatitis, alcohol flush reactions,
exacerbations of rhinitis and, more
seriously and commonly, bronchoconstriction
in patients with a history of asthma.
These reactions occur within 1–60 minutes of ethanol ingestion and are due to: 1)
genetic abnormalities in the metabolism of ethanol which cause the ethanol
metabolite, acetaldehyde, to
accumulate in tissues and trigger the release of histamine,
the evoker of these symptoms; 2) true allergy
reactions to allergens occurring
naturally in, or contaminating, alcoholic beverages, particularly wines and
beers, and 3) unknown causes.[23]
Long-term
Birth defects
Ethanol
is classified as a teratogen.
Cancer
IARC
list ethanol in alcoholic beverages as Group 1 carcinogens and arguments
"There is sufficient evidence for the carcinogenicity
of acetaldehyde (the major
metabolite of ethanol) in experimental animals.".
Other effects
Frequent
drinking of alcoholic beverages has been shown to be a major contributing
factor in cases of elevated blood levels of triglycerides.
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