Cyclooctatetraene

"1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C₈H₈. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy."

"Unlike benzene, C₆H₆, however, cyclooctatetraene, C₈H₈, is not aromatic, although its dianion, C₈H₈^2- (cyclooctatetraenide), is. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions. Benzene, by contrast, characteristically undergoes substitution reactions, much as alkanes do, not additions."