Ketene

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General formula for a ketene.
General formula for a ketene.
Ketene
Ketene

A ketene is an organic compound of the form R2C=C=O. Ketene also refers to the specific compound of this class in which both Rs are hydrogen.

[edit] Properties

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 -150.5 °C (-239 °F) and a boiling point of -56.1 °C (-69 °F).

[edit] Formation

Formation of a ketene from an acyl chloride.
A base, usually triethylamine, removes the acidic proton alpha to the carbonyl group, inducing the formation of the carbon-carbon double bond and the loss of chloride ion.

[edit] Reactions

Ketene is very reactive, tending to attach itself to other molecules in the form of an acetyl group. It will react with itself to form cyclic dimers known as diketenes (oxetanones). It will also undergo [2+2] cycloaddition reactions to electron-rich alkynes to form cyclobutenones.