Acetaldehyde
Chemical compound / From Wikipedia, the free encyclopedia
Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated as MeCHO. 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.
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Names | |||
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Preferred IUPAC name
Acetaldehyde[1] | |||
Systematic IUPAC name
Ethanal[1] | |||
Other names | |||
Identifiers | |||
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3D model (JSmol) |
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ChEBI | |||
ChEMBL | |||
ChemSpider |
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ECHA InfoCard | 100.000.761 | ||
EC Number |
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KEGG |
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PubChem CID |
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RTECS number |
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UNII | |||
CompTox Dashboard (EPA) |
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Properties | |||
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) | ||
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] | ||
-.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 | |||
trigonal planar (sp2) at C1 tetrahedral (sp3) at C2 | |||
2.7 D | |||
Thermochemistry[8] | |||
Heat capacity (C) |
89 J·mol−1·K−1 | ||
Std molar entropy (S⦵298) |
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−1 | ||
Related compounds | |||
Related aldehydes |
Formaldehyde Propionaldehyde | ||
Related compounds |
Ethylene oxide | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards |
potential occupational carcinogen[9] | ||
GHS labelling: | |||
[10] | |||
H224, H319, H335, H351[10] | |||
P210, P261, P281, P305+P351+P338[10] | |||
NFPA 704 (fire diamond) | |||
Flash point | −39.00 °C; −38.20 °F; 234.15 K | ||
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)[9] | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) |
200 ppm (360 mg/m3)[5] | ||
IDLH (Immediate danger) |
2000 ppm[5][9] | ||
Safety data sheet (SDS) | HMDB | ||
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).
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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]