Compounds that contain two fixed double bonds (usually assumed to be between carbon atoms). 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. CH3–CH=C=CH2
buta-1,2-diene. Those in which one or more of the unsaturated carbon atoms is replaced by a heteroatom may be called heterodienes.
See: alkenes, allenes, cumulenes, diols, olefins
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1332 (https://doi.org/10.1351/pac199567081307)