[14]Annulene: cis/trans isomerization via two-twist and nondegenerate planar bond shifting and Möbius conformational minima.

Mechanisms linking dihydrooctalenes and the corresponding [14]annulene isomers have been investigated computationally. CCSD(T)/cc-pVDZ//BHLYP/6-31G* calculations suggest that the cis/trans isomerization steps required by these mechanisms can occur with reasonable activation barriers by pi-bond shifting, in some cases with two-twist topology, and in others in a planar but nondegenerate fashion. In addition, numerous Mobius conformational minima were located for [14]annulene isomers directly related to the mechanisms studied.