Definition of dienes

Compounds that contain two fixed double bonds (usually assumed to be between carbon atoms). See alkenes, olefins. Dienes in which the two double-bond units are linked by one single bond are termed conjugated, e.g. CH2=CH-CH=CH2 buta-1,3-diene. Dienes in which the double bonds are adjacent are called cumulative, e.g. CH3CH=C=CH2 buta-1,2-diene. See also allenes, cumulenes . Those in which one or more of the unsaturated carbon atoms is replaced by a heteroatom may be called heterodienes.