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Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy. Unlike benzene, C 6 H 6, cyclooctatetraene, C 8 H 8, is not aromatic, although its dianion, C 8 H 2− 8 (cyclooctatetraenide), is. Its reactivity is characteristic of an ordinary polyene, i.e. it undergoes addition reactions.
Cyclooctatetraene is an example of a molecule adopting a non-planar geometry to avoid the destabilization that results from antiaromaticity. If it were planar, it would have a single eight-electron π system around the ring, but it instead adopts a boat-like shape with four individual π bonds. [ 3 ]
Benzocyclooctatetraene is a polycyclic hydrocarbon with chemical formula C 12 H 10, composed of fused a benzene ring and a cyclooctatetraene ring. Only the benzene ring is aromatic in this compound. Only the benzene ring is aromatic in this compound.
Fascinatingly, in benzene solution, 1 H NMR reveals a single broadened resonance with a chemical shift at -3.15 ppm. This suggests that the cyclooctatetraene ligands are highly fluxional and some degree of paramagnetism. [1] Fluxional Ring rotation in Fe 3 (COT) 3 depicted by DeKock et al. [13]
Some were originally proposed for benzene itself before the actual structure of benzene was known. Others were later synthesized in lab. Some have been observed to isomerize to benzene, whereas others tend to undergo other reactions instead, or isomerize by ways other than pericyclic reactions. Some known valence isomers of benzene
Using this form of nomenclature 1,3,5,7-cyclooctatetraene is [8]annulene and benzene is [6]annulene (and occasionally referred to as just 'annulene'). [ 2 ] [ 3 ] The discovery that [18]annulene possesses a number of key properties associated with other aromatic molecules was an important development in the understanding of aromaticity as a ...
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This energy is defined as the difference between the total predicted π energy (in benzene 8β) and a hypothetical π energy in which all ethylene units are assumed isolated, each contributing 2β (making benzene 3 × 2β = 6β).