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Acetaldehyde
 
 
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Acetaldehyde (systematically: ethanal) is an organic chemical compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
H
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
3CHO
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or MeCHO. It is a flammable liquid with a fruity smell. Acetaldehyde occurs naturally in ripe fruit
Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. In botany, which is the scientific study of plants, fruits are the ripened Ovary of flowering plants....
, coffee
Coffee

Coffee is a brewed drink prepared from roasted seeds, commonly called coffee beans, of the Coffea. Caffeinated coffee has a stimulating effect in humans....
, and fresh bread
Bread

Bread is a staple food prepared by baking a dough of flour and water. It may be leavened or unleavened. Edible salt, fat and a leavening agent such as yeast are common ingredients, though bread may contain a range of other ingredients: milk, Egg , sugar, spice, fruit , vegetables , Nut or seeds ....
, and is produced by plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s as part of their normal metabolism
Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
. It is popularly known as the chemical that causes hangover
Hangover

A hangover describes the sum of unpleasant physiological effects following heavy consumption of drugs, particularly alcoholic beverages. The most commonly reported characteristics of a hangover include headache, nausea, sensitivity to photophobia and phonophobia, lethargy, dysphoria, and thirst....
s.

other carbonyl compounds, acetaldehyde tautomerizes to give the enol
Enol

Enols are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Enols and carbonyl compounds are in fact isomers; this is called keto-enol tautomerism:...
, ethenol
Ethenol

Ethenol, also called vinyl alcohol, hydroxyethene or hydroxyethylene, is an alcohol with chemical formula 23 and CAS number 557-75-5....
, with Keq
Equilibrium constant

For a general chemical equilibriumthe equilibrium constant can be defined bywhere is the activity of the chemical species A etc . It is conventional to put the activities of the products in the numerator and those of the reactants in the denominator....
 = 6 x 10-5.

he chemical industry, acetaldehyde is used as an intermediate in the production of acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
, certain ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
s, and a number of other chemicals.






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Encyclopedia


Acetaldehyde (systematically: ethanal) is an organic chemical compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
 with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
H
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
3CHO
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or MeCHO. It is a flammable liquid with a fruity smell. Acetaldehyde occurs naturally in ripe fruit
Fruit

The term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. In botany, which is the scientific study of plants, fruits are the ripened Ovary of flowering plants....
, coffee
Coffee

Coffee is a brewed drink prepared from roasted seeds, commonly called coffee beans, of the Coffea. Caffeinated coffee has a stimulating effect in humans....
, and fresh bread
Bread

Bread is a staple food prepared by baking a dough of flour and water. It may be leavened or unleavened. Edible salt, fat and a leavening agent such as yeast are common ingredients, though bread may contain a range of other ingredients: milk, Egg , sugar, spice, fruit , vegetables , Nut or seeds ....
, and is produced by plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s as part of their normal metabolism
Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
. It is popularly known as the chemical that causes hangover
Hangover

A hangover describes the sum of unpleasant physiological effects following heavy consumption of drugs, particularly alcoholic beverages. The most commonly reported characteristics of a hangover include headache, nausea, sensitivity to photophobia and phonophobia, lethargy, dysphoria, and thirst....
s.

Structure

Like other carbonyl compounds, acetaldehyde tautomerizes to give the enol
Enol

Enols are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Enols and carbonyl compounds are in fact isomers; this is called keto-enol tautomerism:...
, ethenol
Ethenol

Ethenol, also called vinyl alcohol, hydroxyethene or hydroxyethylene, is an alcohol with chemical formula 23 and CAS number 557-75-5....
, with Keq
Equilibrium constant

For a general chemical equilibriumthe equilibrium constant can be defined bywhere is the activity of the chemical species A etc . It is conventional to put the activities of the products in the numerator and those of the reactants in the denominator....
 = 6 x 10-5.

Production

In the chemical industry, acetaldehyde is used as an intermediate in the production of acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
, certain ester
Ester

An ester is an often Aroma compound organic chemistry or partially organic compound formed by the reaction between an acid and an alcohol or aromatic alcohol with the elimination of water....
s, and a number of other chemicals. In 1989, US production stood at 740 million pounds (336,000 tonnes). An important production method for acetaldehyde is the Wacker process
Wacker process

The Wacker process or the Hoechst-Wacker process originally referred to the oxidation of ethylene to acetaldehyde by oxygen in water in the presence of a tetrachloropalladate catalysis....
.

The hydration of acetylene
Acetylene

Acetylene is the chemical compound with the symbol carbonhydrogen. It is the simplest alkyne.As an alkyne, acetylene is Saturation because its two carbon atoms are Chemical bond together in a triple bond....
, catalyzed by mercury
Mercury (element)

Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
 salts gives ethenol, which tautomerizes to acetaldehyde. This process was conducted on an industrial scale prior to the Wacker process.

Reactions

Acetaldehyde is a common 2-carbon building block in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
. Because of its small size and its availability as the anhydrous monomer (unlike formaldehyde), it is a common electrophile. With respect to its condensation reactions, acetaldehyde is prochiral
Prochiral

In chemistry, prochiral molecules are those which can be converted from achiral to Chirality in a single step.If two identical substituents are attached to an orbital hybridisation-hybridized atom, the descriptors pro-R and pro-S are used to distinguish between the two....
. It is mainly used as a source of the CH3C+H(OH) synthon
Synthon

A synthon is a concept in retrosynthetic analysis. It is defined as a structural unit within a molecule which is related to a possible organic reaction operation....
 in aldol
Aldol condensation

An Aldol condensation is an organic reaction in which an enolate ion reacts with a carbonyl compound to form a ?-hydroxyaldehyde or ?-hydroxyketone, followed by dehydration to give a conjugated enone....
 and related condensation reactions. Grignard reagents and organolithium compounds react with MeCHO to give hydroxyethyl derivatives. In one of the more spectacular condensation reactions, three equivalents of formaldehyde
Formaldehyde

Formaldehyde is a chemical compound with the chemical formula H2CO. It is the simplest aldehyde. Formaldehyde exists in several forms aside from H2CO: the cyclic trimer trioxane and the polymer Polyoxymethylene....
 add to MeCHO to give pentaerythritol
Pentaerythritol

Pentaerythritol is the organic compound with the chemical formula C4. This white, crystalline polyol is a versatile building block for the preparation of many polyfunctionalized compounds such as the explosive PETN and pentaerythritol triacrylate....
, C(CH2OH)4.

In a Strecker reaction
Strecker amino acid synthesis

The Strecker amino acid synthesis, devised by Adolph Strecker, is a series of chemical reactions that synthesize an amino acid from an aldehyde ....
, acetaldehyde condenses with cyanide
Cyanide

A cyanide is any chemical compound that contains the nitrile , which consists of a carbon atom chemical bond to a nitrogen atom. Inorganic cyanides are hydrogen cyanide salts in which cyanide is generally the anion CN-....
 and ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
 to give, after hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
, the amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 alanine. Acetaldehyde can condense with amines to yield imines, such as the condensation with cyclohexylamine to give N-ethylidenecyclohexylamine. These imines can be used to direct subsequent reactions like an aldol condensation.

It is also an important building block for the synthesis of heterocyclic compounds. A remarkable example is its conversion upon treatment with ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
 to 5-ethyl-2-methylpyridine ("aldehyde-collidine”).

Acetal derivatives

Three molecules of acetaldehyde condense to form “paraldehyde
Paraldehyde

Paraldehyde is the cyclic form of three acetaldehyde molecules . A colourless to pale yellow pungent liquid, it is sparingly soluble in water and highly soluble in alcohol....
,” a cyclic trimer containing C-O single bonds; four condense to form the cyclic molecule called metaldehyde
Metaldehyde

Metaldehyde is a chemical that is commonly used as a pesticide against slugs, snails and other gastropods. Metaldehyde is a cyclic oligomer of acetaldehyde, with IUPAC name: r-2, c-4, c-6, c-8-tetramethyl-1,3,5,7-tetroxoctane....
.

Acetaldehyde forms a stable acetal
Acetal

An acetal is a molecule with two single bonded oxygens attached to the same carbon atom.Traditional usages distinguish ketal from acetal . Current accepted terminology classifies ketals as a subset of acetals....
 upon reaction with ethanol
Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatility , flammable, colorless liquid....
 under conditions that favor dehydration. The product, CH3CH(OCH2CH3)2, is in fact called "acetal," although acetal
Acetal

An acetal is a molecule with two single bonded oxygens attached to the same carbon atom.Traditional usages distinguish ketal from acetal . Current accepted terminology classifies ketals as a subset of acetals....
 is used more widely to describe other compounds with the formula RCH(OR')2.

Biochemistry

In the liver
Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion....
, the enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
 alcohol dehydrogenase
Alcohol dehydrogenase

Alcohol dehydrogenase is an enzyme discovered in the mid-1960s in Drosophila melanogaster. Since then, there has been extensive research on the enzyme....
 converts ethanol
Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatility , flammable, colorless liquid....
 into acetaldehyde, which is then further converted into harmless acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
 by acetaldehyde dehydrogenase
Acetaldehyde dehydrogenase

Acetaldehyde dehydrogenases are dehydrogenase enzymes which catalyze the conversion of acetaldehyde into acetic acid.The oxidation of acetaldehyde to acetate can be summarized as follows:...
. The last steps of alcoholic fermentation
Fermentation (food)

Fermentation in food processing typically refers to the conversion of sugar to alcohol using yeast under anaerobic conditions. A more general definition of fermentation is the chemical conversion of carbohydrates into alcohols or acids....
 in bacteria, plant
Plant

Plants are Life organisms belonging to the Kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae....
s and yeast
Yeast

Yeasts are eukaryote microorganisms classified in the Kingdom fungus, with about 1,500 species currently described; they dominate fungal diversity in the oceans....
 involve the conversion of pyruvate into acetaldehyde by the enzyme pyruvate decarboxylase
Pyruvate decarboxylase

Pyruvate decarboxylase is a homotetrameric enzyme that catalysis the decarboxylation of pyruvic acid to acetaldehyde and carbon dioxide. It is also called 2-oxo-acid carboxylase, alpha-ketoacid carboxylase, and pyruvic decarboxylase....
, followed by the conversion of acetaldehyde into ethanol. The latter reaction is again catalyzed by an alcohol dehydrogenase, now operating in the opposite direction.

Acetaldehyde and hangovers

Most people of East Asia
East Asia

East Asia is a subregion of Asia that can be defined in either Geography or cultural terms. Geography and geopolitically, it covers about 12,000,000 km?, or about 28 percent of the Asian continent, about 15 percent bigger than the area of Europe, though some categorize Tibet, Xinjiang, and Mongolia as Central Asia....
n descent have a mutation
Mutation

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or virus , or can be induced by the organism, itself, by cellular processes such as s...
 in their alcohol dehydrogenase
Alcohol dehydrogenase

Alcohol dehydrogenase is an enzyme discovered in the mid-1960s in Drosophila melanogaster. Since then, there has been extensive research on the enzyme....
 gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
 that makes this enzyme unusually effective at converting ethanol to acetaldehyde, and about half of such people also have a form of acetaldehyde dehydrogenase
Acetaldehyde dehydrogenase

Acetaldehyde dehydrogenases are dehydrogenase enzymes which catalyze the conversion of acetaldehyde into acetic acid.The oxidation of acetaldehyde to acetate can be summarized as follows:...
 that is less effective at converting acetaldehyde to acetic acid. This combination causes them to suffer from the alcohol flush reaction
Alcohol flush reaction

Alcohol flush reaction is a condition in which the body cannot break down ingested alcohol completely, due to a missense mutation polymorphism that encodes the enzyme, acetaldehyde dehydrogenase , normally responsible for breaking down acetaldehyde, a product of the metabolism of alcohol....
, in which acetaldehyde accumulates after drinking, leading to severe and immediate hangover symptoms. These people are therefore less likely to become alcoholics. The drug disulfiram
Disulfiram

Disulfiram is a medication used to support the treatment of chronic alcoholism by producing an acute sensitivity to ethanol. Trade names for disulfiram in different countries are Antabuse and Antabus manufactured by Odyssey Pharmaceuticals....
 (Antabuse) also prevents the oxidation of acetaldehyde to acetic acid, with the same unpleasant effects for drinkers. Antabuse is used as a deterrent for alcoholics who wish to stay sober.

Safety

Acetaldehyde is toxic when applied externally for prolonged periods, an irritant, and a probable carcinogen
Carcinogen

The term carcinogen refers to any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation....
. In addition, acetaldehyde is damaging to DNA and causes abnormal muscle development as it binds to proteins.

Acetaldehyde is an air pollutant
Air pollution

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment, into the Earth's atmosphere....
 resulting from combustion, such as automotive exhaust and tobacco smoke
Tobacco smoking

Tobacco smoking is the inhalation of smoke from burned dried or cured leaves of the tobacco plant, most often in the form of a cigarette. People may smoke casually for pleasure, habitually to satisfy an addiction to the nicotine present in tobacco and to the act of smoking, or in response to social pressure....
. It is also created by thermal degradation of polymers in the plastics processing industry.

See also

  • Wine fault
    Wine fault

    A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage....


External links

  • Hal Kibbey, , Indiana University Research and Creative Activity, Vol. 17 no. 3.