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.
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.
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.
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.