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Acetaldehyde

Acetaldehyde

Overview
Acetaldehyde is an organic chemical compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 CH3CHO or MeCHO. It is one of the most important aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

s, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...

, bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...

, and ripe fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, and is produced by plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s as part of their normal metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

. It is also produced by oxidation of ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 and is popularly believed to be a cause of hangover
Hangover
A hangover describes the sum of unpleasant physiological effects following heavy consumption of alcoholic beverages. The most commonly reported characteristics of a hangover include headache, nausea, sensitivity to light and noise, lethargy, dysphoria, diarrhea and thirst, typically after the...

s from alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 consumption through drinking spirits.
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Encyclopedia
Acetaldehyde is an organic chemical compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 CH3CHO or MeCHO. It is one of the most important aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

s, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...

, bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...

, and ripe fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, and is produced by plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s as part of their normal metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

. It is also produced by oxidation of ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 and is popularly believed to be a cause of hangover
Hangover
A hangover describes the sum of unpleasant physiological effects following heavy consumption of alcoholic beverages. The most commonly reported characteristics of a hangover include headache, nausea, sensitivity to light and noise, lethargy, dysphoria, diarrhea and thirst, typically after the...

s from alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 consumption through drinking spirits. Pathways of exposure include air, water, land or groundwater as well as drink and smoke.

Production


In 2003, global production was about 106 tons/year. The main production method is the oxidation of ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

 via 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 catalyst...

:
2 CH2=CH2 + O2 → 2 CH3CHO

Alternatively, hydration of acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...

, catalyzed by mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 salts gives ethenol, which tautomer
Tautomer
Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond...

izes to acetaldehyde. This industrial route was dominant prior to the Wacker process It is also prepared at smaller levels by both the dehydrogenation
Dehydrogenation
Dehydrogenation is a chemical reaction that involves the elimination of hydrogen . It is the reverse process of hydrogenation. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures....

 and the oxidation of ethanol. Some acetaldehyde forms upon hydrogenation of CO, but this method is not used commercially.

Reactions


Like many other carbonyl compounds, acetaldehyde tautomer
Tautomer
Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond...

izes to give the enol
Enol
Enols are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Alkenes with a hydroxyl group on both sides of the double bond are called enediols. Deprotonated anions of enols are called enolates...

. The enol of acetaldehyde is vinyl alcohol (IUPAC name: ethenol):
CH3CH=O CH2=CHOH

The equilibrium constant is only 6 x 10−5 at room temperature, so that the amount of the enol in a sample of acetaldehyde is very small.

Condensation reactions


Because of its small size and its availability as the anhydrous monomer (unlike formaldehyde), it is a common electrophile 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 molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

. With respect to its condensation reactions, acetaldehyde is prochiral
Prochiral
In stereochemistry, prochiral molecules are those that can be converted from achiral to chiral in a single step.If two identical substituents are attached to a sp3-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 synthetic operation. The term was coined by E.J. Corey...

 in aldol
Aldol condensation
An aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a 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 an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

 add to MeCHO to give pentaerythritol
Pentaerythritol
Pentaerythritol is the organic compound with the formula C5H12O4. This white, crystalline polyol with the neopentane backbone is a versatile building block for the preparation of many polyfunctionalized compounds such as the explosive PETN and pentaerythritol tetraacrylate...

, 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 . The aldehyde is condensed with ammonium chloride in the presence of potassium cyanide to form an α-aminonitrile, which is subsequently hydrolyzed to give...

, acetaldehyde condenses with cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 and ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 to give, after hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

, the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 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 compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 to 5-ethyl-2-methylpyridine ("aldehyde-collidine”).

Acetal derivatives


Three molecules of acetaldehyde condense to form “paraldehyde
Paraldehyde
Paraldehyde is the cyclic trimer of acetaldehyde molecules. Formally, it is a derivative of 1,3,5-trioxane. The corresponding tetramer is metaldehyde. A colourless liquid, it is sparingly soluble in water and highly soluble in alcohol. Paraldehyde slowly oxidizes in air, turning brown and producing...

,” a cyclic trimer containing C-O single bonds. The condensation of four molecules of acetaldehyde give the cyclic molecule called metaldehyde
Metaldehyde
Metaldehyde is an organic compound with the formula 4. It is commonly used as a pesticide against slugs, snails, and other gastropods. It is the cyclic tetramer of acetaldehyde.-Production and properties:...

.

Acetaldehyde forms a stable acetal
Acetal
An acetal is a molecule with two single-bonded oxygen atoms attached to the same carbon atom.Traditional usages distinguish ketals from acetals...

 upon reaction with ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 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 oxygen atoms attached to the same carbon atom.Traditional usages distinguish ketals from 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, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

, the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 alcohol dehydrogenase
Alcohol dehydrogenase
Alcohol dehydrogenases 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...

 oxidizes ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 into acetaldehyde, which is then further oxidized into harmless acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 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:...

. These two oxidation reactions are coupled with the reduction of NAD+ to NADH. In the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

, alcohol dehydrogenase
Alcohol dehydrogenase
Alcohol dehydrogenases 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...

 has a minor role in the oxidation of ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 to acetaldehyde. Instead, the enzyme catalase
Catalase
Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...

 primarily oxidizes ethanol to acetaldehyde. The last steps of alcoholic fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...

 in bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s and yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 involve the conversion of pyruvate into acetaldehyde by the enzyme pyruvate decarboxylase
Pyruvate decarboxylase
Not to be confused with pyruvate dehydrogenase, the enzyme which catalyses the link reaction.Pyruvate decarboxylase is a homotetrameric enzyme that catalyses the decarboxylation of pyruvic acid to acetaldehyde and carbon dioxide in the cytoplasm. It is also called 2-oxo-acid carboxylase,...

, followed by the conversion of acetaldehyde into ethanol. The latter reaction is again catalyzed by an alcohol dehydrogenase, now operating in the opposite direction.

Uses


Traditionally, acetaldehyde was mainly used as a precursor to acetic acid. This application has declined because acetic acid is made more efficiently from methanol by the Monsanto
Monsanto process
The Monsanto process is an important method for the manufacture of acetic acid by catalytic carbonylation of methanol. This process operates at a pressure of 30–60 atm and a temperature of 150–200 °C and gives a selectivity greater than 99%. It was developed 1960 by German BASF and...

 and Cativa process
Cativa process
The Cativa process is a method for the production of acetic acid by the carbonylation of methanol. The technology, which is similar to the Monsanto process, was developed by BP Chemicals and is under license by BP Plc...

es. In terms of condensation reactions, acetaldehyde is an important precursor to pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

 derivatives, pentaerythritol
Pentaerythritol
Pentaerythritol is the organic compound with the formula C5H12O4. This white, crystalline polyol with the neopentane backbone is a versatile building block for the preparation of many polyfunctionalized compounds such as the explosive PETN and pentaerythritol tetraacrylate...

, and crotonaldehyde
Crotonaldehyde
Crotonaldehyde is a chemical compound with the formula CH3CH=CHCHO. The compound is usually sold as a mixture of the E- and Z-isomers, which differ with respect to the relative position of the methyl and formyl groups. The E-isomer is more common...

. Urea and acetaldehyde combine to give a useful resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

. Acetic anhydride
Acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula 2O. Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis...

 reacts with acetaldehyde to give ethylidene diacetate, a precursor to vinyl acetate
Vinyl acetate
Vinyl acetate is an organic compound with the formula CH3COOCH=CH2. A colorless liquid with a pungent odor, it is the precursor to polyvinyl acetate, an important polymer in industry.-Production:...

, which is used to produce polyvinyl acetate
Polyvinyl acetate
Polyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...

.

Safety


Acetaldehyde is toxic when applied externally for prolonged periods, an irritant, and a probable carcinogen. It 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 cause damage to the natural environment or built environment, into the atmosphere....

 resulting from combustion, such as automotive exhaust and tobacco smoke
Tobacco smoking
Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...

. It is also created by thermal degradation of polymers in the plastics processing industry. Acetaldehyde naturally breaks down in the human body but has been shown to excrete in urine of rats.

Acetaldehyde is an irritant of the skin, eyes, mucous membranes, throat and respiratory tract. Symptoms of exposure to this compound include nausea, vomiting, headache. These symptoms may not happen immediately. It has a general narcotic action and large doses can even cause death by respiratory paralysis. It may also cause drowsiness, delirium, hallucinations and loss of intelligence. Exposure may also cause severe damage to the mouth, throat and stomach; accumulation of fluid in the lungs, chronic respiratory disease, kidney and liver damage, throat irritation, dizziness, reddening and swelling of the skin.Not to forget that it is also an anticipated carcinogen.

Indoor air Exposure


Although a relatively weak sensory irritant, acetaldehyde is a common contaminant in workplace, indoor, and ambient environments. It is also a potential carcinogen. Moreover, we spend more than 90% of our time in indoor environments, hence increasing any exposure and consequently the risk to human health.

In a study in France the mean indoor concentration of acetaldehydes measured in 16 homes was approximately seven times higher than the outside acetaldehyde concentration. The living room had a mean of 18.1±17.5 μg m−3 and the bedroom was 18.2±16.9 μg m−3, whereas the outdoor air had a mean concentration of 2.3±2.6 μg m−3. The main sources of acetaldehyde in homes include building materials, laminate, linoleum, wooden varnished, and cork/pine flooring, also found in plastic water based and matt emulsion paints, in wood ceilings, and wooden, particleboard, plywood, pine wood, and chipboard furniture.

It has been concluded that VOCs such as benzene, formaldehyde, acetaldehyde, toluene and xylenes have to be considered as priority pollutants with respect to their health effects. It has been pointed that in renovated or completely new buildings, the VOCs concentration levels are often several orders of magnitude higher. The main sources of acetaldehydes in homes include building materials, laminate, linoleum, wooden varnished, and cork/pine flooring, also found in plastic water based and matt emulsion paints, in wood ceilings, and wooden, particleboard, plywood, pine wood, and chipboard furniture.

Outdoor Air Exposure

The use of acetaldehyde is widespread in different industries, and it may be released into waste water or the air during production, use, transportation and storage. Sources of acetaldehyde include fuel combustion emissions from stationary internal combustion engines and power plants that burn fossil fuels, wood, or trash, oil and gas extraction, refineries, cement kilns, lumber and wood mills and paper mills. Acetaldehyde is also present in automobile and diesel exhaust.

Tobacco smoke


Acetaldehyde is a significant constituent of tobacco smoke. It has been demonstrated to have a synergistic effect with nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

, increasing the onset and tenacity of addiction to cigarette
Cigarette
A cigarette is a small roll of finely cut tobacco leaves wrapped in a cylinder of thin paper for smoking. The cigarette is ignited at one end and allowed to smoulder; its smoke is inhaled from the other end, which is held in or to the mouth and in some cases a cigarette holder may be used as well...

 smoking
Tobacco smoking
Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...

, particularly in adolescents.

Marijuana smoke


Acetaldehyde has been found in Marijuana smoke. They were able to find this by using new chemical techniques that helped them realize that the acetaldehyde present was causing DNA damage in laboratory settings.

Alzheimer's disease


People who have a genetic deficiency for the enzyme responsible for the conversion of acetaldehyde into acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 may have a greater risk of Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

. "These results indicate that the ALDH2
ALDH2
Aldehyde dehydrogenase 2 family , also known as ALDH2, is a human gene found on chromosome 12.-Function:The enzyme encoded by this gene belongs to the aldehyde dehydrogenase family of enzymes that catalyze the chemical transformation from acetaldehyde to acetic acid...

 deficiency is a risk factor for LOAD [late-onset Alzheimer's disease] …"

Alcohol problems


Acetaldehyde derived from the consumption of ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 binds to proteins to form adducts that are linked to organ disease.

The drug disulfiram
Disulfiram
Disulfiram is a drug discovered in the 1920s and used to support the treatment of chronic alcoholism by producing an acute sensitivity to alcohol. Trade names for disulfiram in different countries are Antabuse and Antabus manufactured by Odyssey Pharmaceuticals...

 (Antabuse) prevents the oxidation of acetaldehyde to acetic acid, and it has the same unpleasant effect on drinkers. Antabuse is sometimes used as a deterrent for alcoholics who wish to stay sober.

Carcinogen


Acetaldehyde is a probable carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

 in humans. In 1988 the International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 stated, "There is sufficient evidence for the carcinogenicity of acetaldehyde (the major metabolite of ethanol) in experimental animals." In October 2009 the International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 updated the classification of acetaldehyde stating that acetaldehyde included in and generated endogenously from alcoholic beverages is a Group I human carcinogen. In addition, acetaldehyde is damaging to DNA and causes abnormal muscle development as it binds to proteins.

A study of 818 heavy drinkers found that those who are exposed to more acetaldehyde than normal through a defect in the gene for 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:...

are at greater risk of developing cancers of the upper gastrointestinal tract and liver.

Many microbes produce acetaldehyde from ethanol, but they have a lower capacity to eliminate the acetaldehyde which will then lead to the accumulation of acetaldehyde in saliva during heavy alcohol drinking. Acetaldehyde is also the most abundant carcinogen in tobacco smoke; it is dissolved into the saliva while smoking. Fermented food and many alcoholic beverages will also contain significant amounts of acetaldehyde. Acetaldehyde, derived from mucosal or microbial oxidation of ethanol, tobacco smoke, and diet, appears to act as a cumulative carcinogen in the upper digestive tract of humans.

Stomach cancer


The normal human stomach is free of microbes because of its low pH. Because of bacteria and yeasts that represent the normal oral flora in your mouth they can survive and even proliferate in increasing intragastric pH when adding ethanol. When this happens the bacteria overgrowth results in the form of glucose in the formation of minor concentrations of acetaldehyde in gastric juice. Moreover, poor oral hygiene, heavy drinking and chronic smoking modify oral flora to produce more acetaldehyde from ingested alcohol Acetaldehyde production can increase 6.5 fold to the stomach when there is alcohol involved. Tobacco smoking can also accelerate this process by being an active smoker there are considerable amounts of salivary acetaldehyde that can be expected to reach the stomach through swallowing.

Colon cancer

Chronic alcohol consumption is an established risk factor for colorectal cancer. We also know that most of the acetaldehyde produced in the large intestine is generated from bacterial oxidation of ethanol. In experiments with animals, microbially mediated ethanol oxidation results were high acetaldehyde concentrations in the colon after alcohol administration.

Reduce/Decrease Exposure


Acetaldehyde exposure can be decreased or completely destroyed by using special medical devices that slowly release L-cysteine. Cysteine is a semi-essential sulphur-containing amino acid. A slow-release tablet of cysteine can remove about two-thirds of acetaldehyde after consumption of a moderate dose of alcohol. During smoking, 5 mg cysteine released slowly from is enough to remove all the acetaldehyde from saliva, you can even get these in chewing gum.

External links