Exploring the Boundary between Aromatic and Olefinic Character: Bad News for Second-Order Perturbation Theory and Density Functional Schemes

摘要

The question whether [10]annulene prefers olefinic structures with alternate single and double bonds or aromatic structures like all other small to medium sized uncharged (4n + 2)pi electron homologs (e.g. benzene, [14]annulene) has been controversialfor more than 20 years. On the basis of their experimental observations (NMR data and UV spectra), Masam-une and co-workers concluded that, despite Huckel's (4n + 2)pi electron rule, the isolated all-cis and mono-trans conformations of [10]annulene have alternate single and double bonds.