Ketene

Ketene is an organic compound with the formula CH₂CO. Ketene is very reactive, tending to attach itself to other molecules in the form of an acetyl group. In fact it even shows some tendency to form dimers of the form CH₃COCHCO.

Ketene is colourless, has a sharp odour and causes such things as eye, nose, throat, lung irritation if humans are exposed to concentrated levels. Pulmonary edema has also been noted if these levels are experienced for an extended period of time. It has a melting point of -150.5C (-239F) and a boiling point of -56.1C (-69F).