propenal

Colourless liquid formed during the partial combustion of fats. It is an unsaturated aldehyde, boils at 52°C/125.6°F, has an irritating action on the skin, and its vapours cause a copious flow of tears. It was used in gas form as a chemical weapon in World War I by the French under the codename Papite.

It was fired in artillery shells and hand grenades but its lack of chemical stability made it difficult to store and it saw relatively little service use. It is now used in organic synthesis, pharmaceuticals manufacture, and as a herbicide and tear gas.