A cumulene is an organic compound with three or more cumulative (consecutive) double bonds, for example buta-1,2,3-triene (H₂C=C=C=CH₂). Unlike alkanes and most other organic chains, cumulenes are rigid, which makes them appealing for molecular nanotechnology. Polyynes and allenes are the only other kind of rigid carbon chains. Cumulenes are almost nonexistent on Earth, but they are common in regions of space where hydrogen is rare. See astrochemistry.

functional groups | alkenes | astrochemistry