@C01440@ in which one or more carbon atoms of the cumulative bond system have been replaced by heteroatoms. E.g. O=C=C=C=O, but not CH2=C=O, ketene, nor O=C=O, carbon dioxide, which are heteroallenes.
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1340 [Terms] [Paper]