a system of bonds in which at least one atom is joined by double bonds to two neighboring atoms. Cumulated bonds in theCdarrangement consist of two σ-bonds and two π-bonds. The σ-bonds are formed by two atomic orbitals of the C atom in an sp hybridization state, and therefore the C=C=C arrangement is linear. The π-bonds are formed by two p orbitals, and therefore the planes for these bonds are mutually perpendicular. The classes of organic compounds containing cumulated bonds are as follows:
Compounds that contain cumulated bonds differ from the corresponding compounds with isolated double bonds by greater chemical activity.