What is the structure of the compound produced by the oxidation of ethanal?

This page looks at the oxidation of alcohols using acidified sodium or potassium dichromate(VI) solution. This reaction is used to make aldehydes, ketones and carboxylic acids, and as a way of distinguishing between primary, secondary and tertiary alcohols.

The oxidizing agent used in these reactions is normally a solution of sodium or potassium dichromate(VI) acidified with dilute sulfuric acid. If oxidation occurs, then the orange solution containing the dichromate(VI) ions is reduced to a green solution containing chromium(III) ions. The electron-half-equation for this reaction is as follows:

\[ Cr_2O_7^{2-} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O\]

Primary alcohols can be oxidized to either aldehydes or carboxylic acids, depending on the reaction conditions. In the case of the formation of carboxylic acids, the alcohol is first oxidized to an aldehyde, which is then oxidized further to the acid.

An aldehyde is obtained if an excess amount of the alcohol is used, and the aldehyde is distilled off as soon as it forms. An excess of the alcohol means that there is not enough oxidizing agent present to carry out the second stage, and removing the aldehyde as soon as it is formed means that it is not present to be oxidized anyway!

If you used ethanol as a typical primary alcohol, you would produce the aldehyde ethanal, \(CH_3CHO\). The full equation for this reaction is fairly complicated, and you need to understand the electron-half-equations in order to work it out.

\[ 3CH_3CH_2OH + Cr_2O_7^{2-} + 8H^+ \rightarrow 3CH_3CHO + 2Cr^{3+} + 7H_2O\]

In organic chemistry, simplified versions are often used that concentrate on what is happening to the organic substances. To do that, oxygen from an oxidizing agent is represented as \([O]\). That would produce the much simpler equation:

What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?

It also helps in remembering what happens. You can draw simple structures to show the relationship between the primary alcohol and the aldehyde formed.

What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?

An excess of the oxidizing agent must be used, and the aldehyde formed as the half-way product should remain in the mixture. The alcohol is heated under reflux with an excess of the oxidizing agent. When the reaction is complete, the carboxylic acid is distilled off. The full equation for the oxidation of ethanol to ethanoic acid is as follows:

\[ 3CH_3CH_2OH + 2Cr_2O_7^{2-} + 16H+ \rightarrow 3CH_3COOH + 4Cr^{3+} + 11H_2O\]

The more typical simplified version looks like this:

\[ CH_3CH_2OH + 2[O] \rightarrow CH_3COOH + H_2O\]

Alternatively, you could write separate equations for the two stages of the reaction - the formation of ethanal and then its subsequent oxidation.

\[ CH_3CH_2OH + [O] \rightarrow CH_3CHO + H_2O\]

\[ CH_3CHO + [O] \rightarrow CH_3COOH\]

This is what is happening in the second stage:

What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?

Secondary alcohols are oxidized to ketones - and that's it. For example, if you heat the secondary alcohol propan-2-ol with sodium or potassium dichromate(VI) solution acidified with dilute sulfuric acid, propanone is formed. Changing the reaction conditions makes no difference to the product. Folloiwng is the simple version of the equation, showing the relationship between the structures:

What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?

If you look back at the second stage of the primary alcohol reaction, you will see that an oxygen inserted between the carbon and the hydrogen in the aldehyde group to produce the carboxylic acid. In this case, there is no such hydrogen - and the reaction has nowhere further to go.

Tertiary alcohols are not oxidized by acidified sodium or potassium dichromate(VI) solution - there is no reaction whatsoever. If you look at what is happening with primary and secondary alcohols, you will see that the oxidizing agent is removing the hydrogen from the -OH group, and a hydrogen from the carbon atom is attached to the -OH. Tertiary alcohols don't have a hydrogen atom attached to that carbon.

You need to be able to remove those two particular hydrogen atoms in order to set up the carbon-oxygen double bond.

What is the structure of the compound produced by the oxidation of ethanal?

First, the presence of an alcohol must be confirmed by testing for the -OH group. The liquid would need to be verified as neutral, free of water and that it reacted with solid phosphorus(V) chloride to produce a burst of acidic steamy hydrogen chloride fumes. A few drops of the alcohol would be added to a test tube containing potassium dichromate(VI) solution acidified with dilute sulfuric acid. The tube would be warmed in a hot water bath.

In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol, there is no color change. After heating, the following colors are observed:

What is the structure of the compound produced by the oxidation of ethanal?

A sufficient amount of the aldehyde (from oxidation of a primary alcohol) or ketone (from a secondary alcohol) must be produced to be able to test them. There are various reactions that aldehydes undergo that ketones do not. These include the reactions with Tollens' reagent, Fehling's solution and Benedict's solution, and these reactions are covered on a separate page.

These tests can be difficult to carry out, and the results are not always as clear-cut as the books say. A much simpler but fairly reliable test is to use Schiff's reagent. Schiff's reagent is a fuchsin dye decolorized by passing sulfur dioxide through it. In the presence of even small amounts of an aldehyde, it turns bright magenta.

It must, however, be used absolutely cold, because ketones react with it very slowly to give the same color. If you heat it, obviously the change is faster - and potentially confusing. While you are warming the reaction mixture in the hot water bath, you can pass any vapors produced through some Schiff's reagent.

What is the structure of the compound produced by the oxidation of ethanal?

  • If the Schiff's reagent quickly becomes magenta, then you are producing an aldehyde from a primary alcohol.
  • If there is no color change in the Schiff's reagent, or only a trace of pink color within a minute or so, then you are not producing an aldehyde; therefore, no primary alcohol is present.

Because of the color change to the acidified potassium dichromate(VI) solution, you must, therefore, have a secondary alcohol. You should check the result as soon as the potassium dichromate(VI) solution turns green - if you leave it too long, the Schiff's reagent might start to change color in the secondary alcohol case as well.

Contributors

  • Jim Clark (Chemguide.co.uk)

Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale in industry. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit,[11] and is produced by plants. It is also produced by the partial oxidation of ethanol by the liver enzyme alcohol dehydrogenase and is a contributing cause of hangover after alcohol consumption. Pathways of exposure include air, water, land, or groundwater, as well as drink and smoke.[12] Consumption of disulfiram inhibits acetaldehyde dehydrogenase, the enzyme responsible for the metabolism of acetaldehyde, thereby causing it to build up in the body.

What is the structure of the compound produced by the oxidation of ethanal?
Acetaldehyde

What is the structure of the compound produced by the oxidation of ethanal?

What is the structure of the compound produced by the oxidation of ethanal?

What is the structure of the compound produced by the oxidation of ethanal?

Names Preferred IUPAC name

Acetaldehyde[3]

Systematic IUPAC name

Ethanal[3]

Other names

Acetic aldehyde
Ethyl aldehyde[1]
Acetylaldehyde[2]

Identifiers

CAS Number

  • 75-07-0 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

3D model (JSmol)

  • Interactive image
  • Interactive image

ChEBI

  • CHEBI:15343 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

ChEMBL

  • ChEMBL170365 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

ChemSpider

  • 172 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

ECHA InfoCard 100.000.761
What is the structure of the compound produced by the oxidation of ethanal?
EC Number

  • 200-836-8

IUPHAR/BPS

  • 6277

KEGG

  • C00084 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

PubChem CID

  • 177

RTECS number

  • AB1925000

UNII

  • GO1N1ZPR3B 
    What is the structure of the compound produced by the oxidation of ethanal?
    Y

CompTox Dashboard (EPA)

  • DTXSID5039224
    What is the structure of the compound produced by the oxidation of ethanal?

InChI

  • InChI=1S/C2H4O/c1-2-3/h2H,1H3 

    What is the structure of the compound produced by the oxidation of ethanal?
    Y

    Key: IKHGUXGNUITLKF-UHFFFAOYSA-N 

    What is the structure of the compound produced by the oxidation of ethanal?
    Y

  • InChI=1/C2H4O/c1-2-3/h2H,1H3

    Key: IKHGUXGNUITLKF-UHFFFAOYAB

SMILES

  • O=CC

  • CC=O

Properties

Chemical formula

C2H4O Molar mass 44.053 g·mol−1 Appearance Colourless gas or liquid Odor Ethereal Density 0.784 g·cm−3 (20 °C)[4]

0.7904–0.7928 g·cm−3 (10 °C)[4]

Melting point −123.37 °C (−190.07 °F; 149.78 K) Boiling point 20.2 °C (68.4 °F; 293.3 K)

Solubility in water

miscible Solubility miscible with ethanol, ether, benzene, toluene, xylene, turpentine, acetone
slightly soluble in chloroform log P -0.34 Vapor pressure 740 mmHg (20 °C)[5]Acidity (pKa) 13.57 (25 °C, H2O)[6]

Magnetic susceptibility (χ)

-.5153−6 cm3/g

Refractive index (nD)

1.3316 Viscosity 0.21 mPa-s at 20 °C (0.253 mPa-s at 9.5 °C)[7]Structure

Molecular shape

trigonal planar (sp2) at C1
tetrahedral (sp3) at C2

Dipole moment

2.7 D Thermochemistry[8]

Heat capacity (C)

89 J·mol−1·K−1

Std molar
entropy (So298)

160.2 J·mol−1·K−1

Std enthalpy of
formation (ΔfH⦵298)

−192.2 kJ·mol−1

Gibbs free energy (ΔfG˚)

-127.6 kJ·mol−1Hazards Occupational safety and health (OHS/OSH):

Main hazards

potential occupational carcinogen[10]GHS labelling:

Pictograms

What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?
What is the structure of the compound produced by the oxidation of ethanal?
[9]

Hazard statements

H224, H319, H335, H351[9]

Precautionary statements

P210, P261, P281, P305+P351+P338[9]NFPA 704 (fire diamond)

What is the structure of the compound produced by the oxidation of ethanal?

3

4

3

Flash point −39.00 °C; −38.20 °F; 234.15 K

Autoignition
temperature

175.00 °C; 347.00 °F; 448.15 K[5]Explosive limits 4.0–60% Lethal dose or concentration (LD, LC):

LD50 (median dose)

1930 mg/kg (rat, oral)

LC50 (median concentration)

13,000 ppm (rat),
17,000 ppm (hamster),
20,000 ppm (rat)[10]NIOSH (US health exposure limits):

PEL (Permissible)

200 ppm (360 mg/m3)[5]

IDLH (Immediate danger)

2000 ppm[5][10]Safety data sheet (SDS) HMDB Related compounds

Related aldehydes

Formaldehyde
Propionaldehyde

Related compounds

Ethylene oxide Supplementary data page Acetaldehyde (data page)

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

What is the structure of the compound produced by the oxidation of ethanal?
Y verify (what is 
What is the structure of the compound produced by the oxidation of ethanal?
Y
What is the structure of the compound produced by the oxidation of ethanal?
N ?)

Infobox references

The International Agency for Research on Cancer (IARC) has listed acetaldehyde as a Group 1 carcinogen.[13] Acetaldehyde is "one of the most frequently found air toxins with cancer risk greater than one in a million".[14]

Acetaldehyde was first observed by the Swedish pharmacist/chemist Carl Wilhelm Scheele (1774);[15] it was then investigated by the French chemists Antoine François, comte de Fourcroy and Louis Nicolas Vauquelin (1800),[16] and the German chemists Johann Wolfgang Döbereiner (1821, 1822, 1832)[17] and Justus von Liebig (1835).[18][19] In 1835, Liebig named it "aldehyde";[20] the name was later altered to "acetaldehyde".[21]

In 2003, global production was about 1 million tonnes. Before 1962, ethanol and acetylene were the major sources of acetaldehyde. Since then, ethylene is the dominant feedstock.[22]

The main method of production is the oxidation of ethylene by the Wacker process, which involves oxidation of ethylene using a homogeneous palladium/copper system:

2 CH2=CH2 + O2 → 2 CH3CHO

In the 1970s, the world capacity of the Wacker-Hoechst direct oxidation process exceeded 2 million tonnes annually.

Smaller quantities can be prepared by the partial oxidation of ethanol in an exothermic reaction. This process typically is conducted over a silver catalyst at about 500–650 °C.[22]

CH3CH2OH + 12 O2 → CH3CHO + H2O

This method is one of the oldest routes for the industrial preparation of acetaldehyde.

Other methods

Hydration of acetylene

Prior to the Wacker process and the availability of cheap ethylene, acetaldehyde was produced by the hydration of acetylene.[23] This reaction is catalyzed by mercury(II) salts:

C2H2 + Hg2+ + H2O → CH3CHO + Hg

The mechanism involves the intermediacy of vinyl alcohol, which tautomerizes to acetaldehyde. The reaction is conducted at 90–95 °C, and the acetaldehyde formed is separated from water and mercury and cooled to 25–30 °C. In the wet oxidation process, iron(III) sulfate is used to reoxidize the mercury back to the mercury(II) salt. The resulting iron(II) sulfate is oxidized in a separate reactor with nitric acid.[22]

Dehydrogenation of ethanol

Traditionally, acetaldehyde was produced by the partial dehydrogenation of ethanol:

CH3CH2OH → CH3CHO + H2

In this endothermic process, ethanol vapor is passed at 260–290 °C over a copper-based catalyst. The process was once attractive because of the value of the hydrogen coproduct,[22] but in modern times is not economically viable.

Hydroformylation of methanol

The hydroformylation of methanol with catalysts like cobalt, nickel, or iron salts also produces acetaldehyde, although this process is of no industrial importance. Similarly noncompetitive, acetaldehyde arises from synthesis gas with modest selectivity.[22]

 

Tautomeric equilibrium between acetaldehyde and vinyl alcohol.

Like many other carbonyl compounds, acetaldehyde tautomerizes to give an enol (vinyl alcohol; IUPAC name: ethenol):

CH3CH=O ⇌ CH2=CHOH                 ∆H298,g = +42.7 kJ/mol

The equilibrium constant is 6×10−7 at room temperature, thus that the relative amount of the enol form in a sample of acetaldehyde is very small.[24] At room temperature, acetaldehyde (CH3CH=O) is more stable than vinyl alcohol (CH2=CHOH) by 42.7 kJ/mol:[25] Overall the keto-enol tautomerization occurs slowly but is catalyzed by acids.

Photo-induced keto-enol tautomerization is viable under atmospheric or stratospheric conditions. This photo-tautomerization is relevant to the earth's atmosphere, because vinyl alcohol is thought to be a precursor to carboxylic acids in the atmosphere.[26][27]

Condensation reactions

Acetaldehyde is a common electrophile in organic synthesis.[28] In condensation reactions, acetaldehyde is prochiral. It is used primarily as a source of the "CH3C+H(OH)" synthon in aldol and related condensation reactions.[29] Grignard reagents and organolithium compounds react with MeCHO to give hydroxyethyl derivatives.[30] In one of the more spectacular condensation reactions, three equivalents of formaldehyde add to MeCHO to give pentaerythritol, C(CH2OH)4.[31]

In a Strecker reaction, acetaldehyde condenses with cyanide and ammonia to give, after hydrolysis, the amino acid alanine.[32] Acetaldehyde can condense with amines to yield imines; for example, with cyclohexylamine to give N-ethylidenecyclohexylamine. These imines can be used to direct subsequent reactions like an aldol condensation.[33]

It is also a building block in the synthesis of heterocyclic compounds. In one example, it converts, upon treatment with ammonia, to 5-ethyl-2-methylpyridine ("aldehyde-collidine").[34]

Polymeric forms

 

 

Cyclic oligomers of acetaldehyde (CH3CHO)n: paraldehyde (n = 3, left) and metaldehyde (n = 4, right)

Three molecules of acetaldehyde condense to form "paraldehyde", a cyclic trimer containing C-O single bonds. Similarly condensation of four molecules of acetaldehyde give the cyclic molecule metaldehyde. Paraldehyde can be produced in good yields, using a sulfuric acid catalyst. Metaldehyde is only obtained in a few percent yield and with cooling, often using HBr rather than H2SO4 as the catalyst. At -40 °C in the presence of acid catalysts, polyacetaldehyde is produced.[22] There are two stereomers of paraldehyde and four of metaldehyde.

The German chemist Valentin Hermann Weidenbusch (1821–1893) synthesized paraldehyde in 1848 by treating acetaldehyde with acid (either sulfuric or nitric acid) and cooling to 0°C. He found it quite remarkable that when paraldehyde was heated with a trace of the same acid, the reaction went the other way, recreating acetaldehyde.[35]

Acetal derivatives

 

Conversion of acetaldehyde to 1,1-diethoxyethane, R1 = CH3, R2 = CH3CH2

Acetaldehyde forms a stable acetal upon reaction with ethanol under conditions that favor dehydration. The product, CH3CH(OCH2CH3)2, is formally named 1,1-diethoxyethane but is commonly referred to as "acetal".[36] This can cause confusion as "acetal" is more commonly used to describe compounds with the functional groups RCH(OR')2 or RR'C(OR'')2 rather than referring to this specific compound – in fact, 1,1-diethoxyethane is also described as the diethyl acetal of acetaldehyde.

Precursor to vinylphosphonic acid

Acetaldehyde is a precursor to vinylphosphonic acid, which is used to make adhesives and ion conductive membranes. The synthesis sequence begins with a reaction with phosphorus trichloride:[37]

PCl3 + CH3CHO → CH3CH(O−)PCl3+ CH3CH(O−)PCl3+ + 2 CH3CO2H → CH3CH(Cl)PO(OH)2 + 2 CH3COCl CH3CH(Cl)PO(OH)2 → CH2=CHPO(OH)2 + HCl

In the liver, the enzyme alcohol dehydrogenase oxidizes ethanol into acetaldehyde, which is then further oxidized into harmless acetic acid by acetaldehyde dehydrogenase. These two oxidation reactions are coupled with the reduction of NAD+ to NADH.[38] In the brain, the enzyme catalase is primarily responsible for oxidizing ethanol to acetaldehyde, and alcohol dehydrogenase plays a minor role.[38] The last steps of alcoholic fermentation in bacteria, plants, and yeast involve the conversion of pyruvate into acetaldehyde and carbon dioxide by the enzyme pyruvate 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.

Traditionally, acetaldehyde was mainly used as a precursor to acetic acid. This application has declined because acetic acid is produced more efficiently from methanol by the Monsanto and Cativa processes. Acetaldehyde is an important precursor to pyridine derivatives, pentaerythritol, and crotonaldehyde. Urea and acetaldehyde combine to give a useful resin. Acetic anhydride reacts with acetaldehyde to give ethylidene diacetate, a precursor to vinyl acetate, which is used to produce polyvinyl acetate.[22]

The global market for acetaldehyde is declining. Demand has been impacted by changes in the production of plasticizer alcohols, which has shifted because n-butyraldehyde is less often produced from acetaldehyde, instead being generated by hydroformylation of propylene. Likewise, acetic acid, once produced from acetaldehyde, is made predominantly by the lower-cost methanol carbonylation process.[39] The impact on demand has led to increase in prices and thus slowdown in the market.

 

Production of Acetaldehyde

Consumption of acetaldehyde (103 t) in 2003[22]
(* Included in others -glyoxal/glyoxalic acid, crotonaldehyde, lactic acid, n-butanol, 2-ethylhexanol)

Product USA Mexico W. Europe Japan Total
Acetic Acid/Acetic anhydride - 11 89 47 147
Acetate esters 35 8 54 224 321
Pentaerythritol 26 43 11 80
Pyridine and pyridine bases 73 10 * 83
Peracetic acid 23 * 23
1,3-Butylene glycol 14 * 14
Others 5 3 10 80 98
Total 176 22 206 362 766

China is the largest consumer of acetaldehyde in the world, accounting for almost half of global consumption in 2012. Major use has been the production of acetic acid. Other uses such as pyridines and pentaerythritol are expected to grow faster than acetic acid, but the volumes are not large enough to offset the decline in acetic acid. As a consequence, overall acetaldehyde consumption in China may grow slightly at 1.6% per year through 2018. Western Europe is the second-largest consumer of acetaldehyde worldwide, accounting for 20% of world consumption in 2012. As with China, the Western European acetaldehyde market is expected to increase only very slightly at 1% per year during 2012–2018. However, Japan could emerge as a potential consumer for acetaldehyde in next five years due to newfound use in commercial production of butadiene. The supply of butadiene has been volatile in Japan and the rest of Asia. This should provide the much needed boost to the flat market, as of 2013.[40]

The threshold limit value is 25ppm (STEL/ceiling value) and the MAK (Maximum Workplace Concentration) is 50 ppm. At 50 ppm acetaldehyde, no irritation or local tissue damage in the nasal mucosa is observed. When taken up by the organism, acetaldehyde is metabolized rapidly in the liver to acetic acid. Only a small proportion is exhaled unchanged. After intravenous injection, the half-life in the blood is approximately 90 seconds.[22]

Dangers

Toxicity

Many serious cases of acute intoxication have been recorded.[22] Acetaldehyde naturally breaks down in the human body.[12][41]

Irritation

Acetaldehyde is an irritant of the skin, eyes, mucous membranes, throat, and respiratory tract. This occurs at concentrations as low as 1000 ppm. Symptoms of exposure to this compound include nausea, vomiting, and headache. These symptoms may not happen immediately. The perception threshold for acetaldehyde in air is in the range between 0.07 and 0.25 ppm.[22] At such concentrations, the fruity odor of acetaldehyde is apparent. Conjunctival irritations have been observed after a 15-minute exposure to concentrations of 25 and 50 ppm, but transient conjunctivitis and irritation of the respiratory tract have been reported after exposure to 200 ppm acetaldehyde for 15 minutes.

Carcinogenicity

Acetaldehyde is carcinogenic in humans.[42][43] In 1988 the International Agency for Research on Cancer stated, "There is sufficient evidence for the carcinogenicity of acetaldehyde (the major metabolite of ethanol) in experimental animals."[44] In October 2009 the International Agency for Research on Cancer updated the classification of acetaldehyde stating that acetaldehyde included in and generated endogenously from alcoholic beverages is a Group I human carcinogen.[45] In addition, acetaldehyde is damaging to DNA[46] and causes abnormal muscle development as it binds to proteins.[47]

DNA crosslinks

Acetaldehyde induces DNA interstrand crosslinks, a form of DNA damage. These can be repaired by either of two replication-coupled DNA repair pathways.[48] The first is referred to as the FA pathway, because it employs gene products defective in Fanconi's anemia patients. This repair pathway results in increased mutation frequency and altered mutational spectrum.[48] The second repair pathway requires replication fork convergence, breakage of the acetaldehyde crosslink, translesion synthesis by a Y-family DNA polymerase and homologous recombination.[48]

Aggravating factors

Alzheimer's disease

People with a genetic deficiency for the enzyme responsible for the conversion of acetaldehyde into acetic acid may have a greater risk of Alzheimer's disease. "These results indicate that the ALDH2 deficiency is a risk factor for LOAD [late-onset Alzheimer's disease] ..."[49]

Genetic conditions

A study of 818 heavy drinkers found that those exposed to more acetaldehyde than normal through a genetic variant of the gene encoding for alcohol dehydrogenase are at greater risk of developing cancers of the upper gastrointestinal tract and liver.[50]

Disulfiram

The drug disulfiram (Antabuse) inhibits acetaldehyde dehydrogenase, an enzyme that oxidizes the compound into acetic acid. Metabolism of ethanol forms acetaldehyde before acetaldehyde dehydrogenase forms acetic acid, but with the enzyme inhibited, acetaldehyde accumulates. If one consumes ethanol while taking disulfiram, the hangover effect of ethanol is felt more rapidly and intensely. As such, disulfiram is sometimes used as a deterrent for alcoholics wishing to stay sober.

Sources of exposure

Indoor air

Acetaldehyde is a potential contaminant in workplace, indoors, and ambient environments. Moreover, the majority of humans spend more than 90% of their time in indoor environments, increasing any exposure and the risk to human health.[51]

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.[citation needed]

It has been concluded that volatile organic compounds (VOC) such as benzene, formaldehyde, acetaldehyde, toluene, and xylenes have to be considered 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, PVC flooring, varnished wood flooring, and varnished cork/pine flooring (found in the varnish, not the wood). It is also found in plastics, oil-based and water-based paints, in composite wood ceilings, particle-board, plywood, treated pine wood, and laminated chipboard furniture.[52]

Outdoor air

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.[53] Acetaldehyde is also present in automobile and diesel exhaust.[54] As a result, acetaldehyde is "one of the most frequently found air toxics with cancer risk greater than one in a million".[14]

Tobacco smoke

Natural tobacco polysaccharides, including cellulose, have been shown to be the primary precursors making acetaldehyde a significant constituent of tobacco smoke.[55][56] It has been demonstrated to have a synergistic effect with nicotine in rodent studies of addiction.[57][58] Acetaldehyde is also the most abundant carcinogen in tobacco smoke; it is dissolved into the saliva while smoking.

Cannabis smoke

Acetaldehyde has been found in cannabis smoke. This finding emerged through the use of new chemical techniques that demonstrated the acetaldehyde present was causing DNA damage in laboratory settings.[59]

Alcohol consumption

Many microbes produce acetaldehyde from ethanol, but they have a lower capacity to eliminate the acetaldehyde, which can lead to the accumulation of acetaldehyde in saliva, stomach acid, and intestinal contents. Fermented food and many alcoholic beverages can 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.[60] According to European Commission's Scientific Committee on Consumer Safety's (SCCS) "Opinion on Acetaldehyde" (2012) the cosmetic products special risk limit is 5 mg/L and acetaldehyde should not be used in mouth-washing products.[61]

Plastics

Acetaldehyde can be produced by the photo-oxidation of polyethylene terephthalate (PETE), via a Type II Norrish reaction.[62]

 

Although the levels produced by this process are minute acetaldehyde has an exceedingly low taste/odor threshold of around 20–40 ppb and can cause an off-taste in bottled water.[63] The level at which an average consumer could detect acetaldehyde is still considerably lower than any toxicity.[64]

Candida Overgrowth

Candida albicans in patients with potentially carcinogenic oral diseases has been shown to produce acetaldehyde in quantities sufficient to cause problems.[65]

  • Alcohol dehydrogenase
  • Disulfiram-like drug
  • Formaldehyde
  • Paraldehyde
  • Wine fault

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  12. ^ a b "Chemicals in the Environment: Acetaldehyde (CAS NO. 75-07-0)". epa.gov. Office of Pollution Prevention and Toxics, United States Environmental Protection Agency. August 1994. Archived from the original on 17 August 2002. Retrieved 22 January 2011.
  13. ^ List of IARC Group 1 carcinogens
  14. ^ a b Zhou, Ying; Li, Chaoyang; Huijbregts, Mark A. J.; Mumtaz, M. Moiz (7 October 2015). "Carcinogenic Air Toxics Exposure and Their Cancer-Related Health Impacts in the United States". PLOS ONE. 10 (10): e0140013. Bibcode:2015PLoSO..1040013Z. doi:10.1371/journal.pone.0140013. PMC 4596837. PMID 26444872.
  15. ^ Scheele, C. W. (1774) "Om Brunsten eller Magnesia nigra och dess egenskaper" (On brown-stone or black magnesia [i.e., manganese ore] and its properties), Kungliga Svenska vetenskapsakademiens handlingar (Proceedings of the Royal Swedish Academy of Sciences), 35 : 89–116; 177–194. On pages 109–110, Scheele mentions that refluxing ("digesting") ethanol (Alkohol vini) with manganese dioxide (Brunsten) and either hydrochloric acid (Spirtus salis) or sulfuric acid (Spiritus Vitrioli) produces a smell like "Aether nitri" (ethanol treated with nitric acid). Later investigators realized that Scheele had produced acetaldehyde.
  16. ^ Note:
    • Dabit, a pharmacist in Nantes, France, performed a series of experiments and concluded that acetaldehyde was formed when hydrogen in ethanol combined with oxygen in sulfuric acid to form water: Dabit (1800) "Extrait du mémoire du cit. Dabit sur l'éther" (Extract of the memoir by citizen Dabit on ether), Annales de Chimie, 34 : 289–305.
    • Fourcroy and Vauquelin stated that sulfuric acid was not consumed in the production of acetaldehyde: Fourcroy and Vauquelin (1800), "Sur l'éther préparé à la manière du cit. Dabit" (On the ether prepared in the way of citizen Dabit), Annales de Chimie, 34 : 318-332.
  17. ^ See:
    • (Döbereiner) (1821) "Neue Aether" (A new ether), Journal für Chemie und Physik, 32 : 269–270. Döbereiner named the new "ether" "Sauerstoffäther" (oxygen-ether).
    • (Döbereiner) (1822) "Döbereiner's Apparat zur Darstellung des Sauerstoffaethers" (Döbereiner's apparatus for the preparation of oxygen-ether), Journal für Chemie und Physik, 34 : 124–125.
    • Döbereiner, J. W. (1832) "Bildung des Sauerstoff-Aethers durch atmosphärische Oxidation des Alkohols" (Formation of oxy-ether by atmospheric oxidation of alcohol), Journal für Chemie und Physik, 64 : 466–468. In this paper, Döbereiner made acetaldehyde by exposing ethanol vapor to air in the presence of platinum black.
  18. ^ Liebig, Justus (1835) "Ueber die Producte der Oxydation des Alkohols" (On the products of oxidation of alcohol [i.e., ethanol]), Annalen der Chemie, 14 : 133–167.
  19. ^ Brock, William H. (1997) Justus von Liebig: The Chemical Gatekeeper. Cambridge, England: Cambridge University Press, pp. 83–84.
  20. ^ Liebig, J. (1835) "Sur les produits de l'oxidation de l'alcool" (On the products of the oxidation of alcohol), Annales de Chimie et de Physique, 59 : 289–327. From p. 290: "Je le décrirai dans ce mémoire sous le nom d'aldehyde; ce nom est formé de alcool dehydrogenatus." (I will describe it in this memoir by the name of aldehyde; this name is formed from alcohol dehydrogenatus.)
  21. ^ The name change occurred at least as early as 1868. See, for example: Eugen F. von Gorup-Besanez, ed., Lehrbuch der organischen Chemie für den Unterricht auf Universitäten ... [Textbook of Organic Chemistry for Instruction at Universities ...], 3rd ed. (Braunschweig, Germany: Friedrich Vieweg und Sohn, 1868), vol. 2, p. 88.
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  43. ^ Scientific Committee on Cosmetic Products and Non-Food Products (25 May 2004). "Opinion of the Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers Concerning Acetaldehyde" (PDF). p. 11. Retrieved 28 September 2011.
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  • International Chemical Safety Card 0009
  • NIOSH Pocket Guide to Chemical Hazards
  • Methods for sampling and analysis
  • IARC Monograph: "Acetaldehyde"
  • Hal Kibbey, Genetic Influences on Alcohol Drinking and Alcoholism, Indiana University Research and Creative Activity, Vol. 17 no. 3.
  • United States Food and Drug Administration (FDA) information for acetaldehyde
  • Acetaldehyde production process flow sheet by ethylene oxidation method

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