3D model (Jmol)
|Molar mass||234.34 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Cyclooctadecanonaene or annulene is an annulene with chemical formula C
18. This hydrocarbon obeys Hückel's rule and is, therefore, an aromatic compound. Theoretical studies show that 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 annulene. The compound was first synthesised by Franz Sondheimer.
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. 
- Ivanov, A.; Boldyrev. A (2014). "Deciphering aromaticity in porphyrinoids via adaptive natural density partitioning". Org. Biomol. Chem. doi:10.1039/C4OB01018C.
- In the literature and some internet references, Sondheimer is sometimes misspelled as Sandheimer.
- Sondheimer, F., Wolovsky, R. and Amiel, Y. (1962). "Unsaturated Macrocyclic Compounds. XXIII. The Synthesis of the Fully Conjugated Macrocyclic Polyenes Cyclooctadecanonaene (Annulene), Cyclotetracosadodecaene (Annulene), and Cyclotriacontapentadecaene (Annulene).". J. Am. Chem. Soc. 68 (2): 274–284. doi:10.1021/ja00861a030.
- K. Stöckel and F. Sondheimer (1988). "Annulene". Org. Synth.; Coll. Vol., 6, p. 68