An allene is a hydrocarbon in which one atom of carbon is connected by double bonds with two other atoms of carbon. Allene also is the common name for the parent compound of this series, 1,2-propadiene.

Such pair of bonds make allenes much more reactive than other alkenes. For example, their reactivity with gaseous chlorine is more like the reactivity of alkynes.

In the image at the right, if groups "a" and "b" replace one of the hydrogens on the left and right sides, the molecule will be chiral if "a" is not identical to "b". This is because the two sets of groups are perpendicular to each other, and thus the molecule has no mirror plane.

Compounds with more than two adjacent carbon-carbon double bonds are called cumulenes.

External links

• Stereochemistry study guide
• Synthesis of allenes

Dienes

ألين | Allène | 不飽和結合 | Allen | Allen