Acetaldehyde
Encyclopedia : A : AC : ACE : Acetaldehyde
| Acetaldehyde | ||
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| Systematic name | Acetaldehyde | |
| Other IUPAC name | Ethanal | |
| Chemical formula | CH3CHO | |
| SMILES | CC=O | |
| Molecular mass | 44.05 g/mol | |
| Appearance | Colorless liquid Pungent, fruity odor | |
| CAS number | [75-07-0] | |
| Properties | ||
| Density | 0.788 g/cm3 | |
| Solubility in water | ? g/100 ml (? °C) | |
| Melting point | −124 °C | |
| Boiling point | 26 °C | |
| Viscosity | ? cP at ? °C | |
| Structure | ||
| Molecular shape | ? | |
| Dipole moment | ? D | |
| Hazards | ||
| MSDS | External MSDS | |
| EU classification | Very flammable (F+) Harmful (Xn) Carc. Cat. 3 | |
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properties
data
Solid, liquid, gas
Propionaldehyde
In the liver, the enzyme alcohol dehydrogenase converts ethanol into acetaldehyde, which is then further converted into harmless acetic acid by acetaldehyde dehydrogenase. Acetaldehyde is more toxic than ethanol and is responsible for many hangover symptoms. N-Acetylcysteine (NAC) is known to assist in processing acetaldehyde in the body and therefore can help to relieve hangover symptoms. L-Cysteine and L-glutamine, which each contain a thiol group, can force conversion back into ethanol, to similar effect.
Some people of East Asian descent have a mutation in their acetaldehyde dehydrogenase gene, making this enzyme less effective. In these people, acetaldehyde accumulates after drinking, leading to severe and immediate hangover symptoms. These people are therefore less likely to become alcoholics. The drug Antabuse (disulfiram) also prevents the oxidation of acetaldehyde to acetic acid, with the same unpleasant effects for drinkers. It is used in the treatment of certain alcoholics.
The last steps of alcoholic fermentation in bacteria, plants and yeast involve the conversion of pyruvate into acetaldehyde by the enzyme pyruvate decarboxylase, followed by the conversion of acetaldehyde into ethanol. The latter reaction is again catalyzed by alcohol dehydrogenase, now operating in the opposite direction.
In the chemical industry, acetaldehyde is mainly used as an intermediate in the production of acetic acid, certain esters, and a number of other chemicals. In 1989, US production stood at 740 million pounds (336,000 t).
When exposed to acetaldehyde vapors, humans develop irritation of the eyes, skin and the respiratory tract. Acetaldehyde is an air pollutant, emitted by cars and certain production facilities. It is also contained in tobacco smoke, contributing to the smoke's addictive properties.
Three molecules of acetaldehyde can form the cyclic paraldehyde, and four can form the cyclic acetaldehyde tetramer.
Cancer link
After some experiments with animals, acetaldehyde is classified as a probable carcinogen.See also
External links
- [International Chemical Safety Card 0009]
- [National Pollutant Inventory - Acetaldehde]
- [NIOSH Pocket Guide to Chemical Hazards]
- [IARC Monograph: "Acetaldehyde"]
- [EPA factsheet about 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]
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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