Aromaticity: The Alternating CC Bond Length Structures of [14]‐, [18]‐, and [22]Annulene

Abstract

First among unequals: Equal CC bond lengths, as found in benzene, are not necessary for aromaticity. [18]Annulene is the next Hückel monocycle where D6h symmetry is possible topologically (see picture). However, this widely accepted structure of [18]annulene is not correct. The 1H NMR chemical shifts and energy computations show that [18]annulene prefers CC bond-length alternation and C2 symmetry. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z54188_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.