Acrolein

Acrolein

[uh-kroh-lee-in]

Acrolein (systematic name: 2-propenal) is the simplest unsaturated aldehyde. It is produced widely but is most often immediately reacted with other products due to its instability and toxicity. It has a piercing, disagreeable, acrid smell similar to that of burning fat.

Synthesis

Acrolein is prepared industrially by oxidation of propene. Efforts are underway to use propane as feedstock for the synthesis, however, this is more difficult. Several million tonnes of acrolein are produced each year.

When glycerol is heated to 280 °C, it decomposes into acrolein. Acrolein may also be produced on lab scale by the reaction of potassium bisulfate on glycerol (glycerine).

Uses

Acrolein is used in the preparation of polyester resin, polyurethane, propylene glycol, acrylic acid, acrylonitrile, and glycerol. Acrolein tends to polymerize when left at room temperature, leaving a gummy yellowish residue with a putrid odor. It is also thought to be an intermediate in the Skraup synthesis of quinolines, but is rarely used as such due to its instability. Acrolein is sometimes used as a fixative in preparation of biological specimens for electron microscopy.

Health risks

Acrolein is a severe pulmonary irritant and lacrimating agent. It has been used as a chemical weapon during World War I. It is, however, not outlawed by the Chemical Weapons Convention. Acrolein is also a metabolite of the chemotherapy drug cyclophosphamide, and is associated with hemorrhagic cystitis. Skin exposure to acrolein causes serious damage. Acrolein concentrations of 2 ppm are immediately harmful. Acrolein is not a suspected human carcinogen; no studies have been conducted on the carcinogenic effects of acrolein on humans, but studies on rats have shown an increase in cancerous tumors from ingestion, but not from inhalation. In October 2006, researchers found connections between acrolein in the smoke from tobacco cigarettes and the risk of lung cancer.

Acrolein test

Acrolein test is a test for the presence of glycerin or fats. A sample is heated with potassium bisulfate, and acrolein is released if the test is positive. When a fat is heated strongly in the presence of a dehydrating agent such as KHSO4, the glycerol portion of the molecule is dehydrated to form the unsaturated aldehyde, acrolein (CH2=CH-CHO), which has the peculiar odor of burnt grease.

References

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