Characteristics of aromatic compounds include:
Must be Cyclic and planar
Must have (4n+2)π electrons (n=1,2,3,4,....)
Resist Addition but Prefer Substitution.
Must Possess Resonance Energy.
Due to severe non-bonded interactions between the internal hydrogen (as shown in figure), the ring assumes non-planar geometry in 10-annulene, hence, it is not an aromatic compound.




