quinone CHEBI:13684 quinone Chinon Compounds having a fully conjugated cyclic dione structure, such as that of benzoquinones, derived from aromatic compounds by conversion of an even number of ‒CH= groups into ‒C(=O)‒ groups with any necessary rearrangement of double bonds (polycyclic and heterocyclic analogues are included). quinones quinones CHEBI:26517 cyclic ketone