Cyclooctadecanonaene or [18]annulene is an annulene with chemical formula C
18H
18. This hydrocarbon obeys Hückel's rule and is, therefore, an aromatic compound. Theoretical studies show that [18]annulene has only three completely delocalized π bonds associated with its aromaticity, while other six π bonds represent the conjugated 3c-2e π bonds on the periphery of [18]annulene. The compound was first synthesised by Franz Sondheimer.
Reactions
The original synthesis started by the Eglinton reaction of the di-alkyne 1,5-hexadiyne with copper(II) acetate in pyridine to give the trimer, followed by deprotonation and isomerization with potassium tert-butoxide in tert-butanol and was concluded with hydrogen organic reduction with the Lindlar catalyst.
References
Cyclooctadecanonaene Wikipedia(Text) CC BY-SA