Acetaldehyde
 
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H3C-CHO
Ethanal, ethyl aldehyde, acetic aldehyde, C2H4O M 44,1 g/Mol
GHS-symbol inflammableGHS-symbol: harmfulGHS-symbol: exclamation mark

Physical Characteristics

Colorless, stinging smelling liquid.

Mp. -123 degrees, Bp. 21 degrees, specific gravity 0.78 g/cm3, flash point -27 degrees

Ignition temperature 140 degrees, explosion limit 4 to 57 Vol%, vapour pressure (20 degrees) 1007 mbar

Classification

CAS No. 75-07-0, EC No. 200-836-8, Annex I Index No. 605-003-00-6, R 12-36/37-40, S 16-33-36/37, high-inflammatory, attractive, injurious to health, MAK 50 ml/m3/91 mg/m3

LD50 (rat) 661 mg/kg, storage under +15 degrees

Biological Importance

Acetaldehyde (Ethanal) is the primary oxidation product of ethanol, which is continued to be oxidized to acetic acid. In the body, the oxidation of alcohol to acetaldehyde is mainly located in the liver in presence of the enzyme alcoholdehydrogenase (ADH). At the same time the coenzyme NAD is reduced to the NADH. This reaction is also used for the determination of the blood alcohol concentration by means of the ADH procedure.

The formed acetaldehyde is detoxicated for his part under co-operation of the enzyme aldehydedehydrogenase (ALDH) to biologically activated acetic acid (acetyl coenzyme A), whereby the concentration of free acetaldehyde in the body remains normally very small. With enyzmatic defects or by artificial blocking of the enzyme it comes to incompatibility reactions (acetaldehyde syndrome).

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Last Update: 10/29/2010 - IMPRINT - FAQ