Allene
From Freepedia
An allene is a hydrocarbon in which one atom of carbon is connected by double bonds with two other atoms of carbon.
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 right, if groups "a" and "b" replace the hydrogens on the left and right side, the molecule will be chiral if "a" is not identical to "b". This is due to the two sets of groups being perpendicular to each other, and thus the molecule has no mirror plane.
