Benzene [6]-Annulene. A perfect example of cyclic planar molecule with uninterrupted ring of p orbital bearing atoms; 6 electron system (4n+2, n = 1) Aromatic 8 membered ring, Cyclooctatetraene or [8]-annulene 8 π electron system;If completely planar, this molecule will become antiaromatic (bond angle for planar structrure = 135o which can give considerable angle strain in a cyclic structure involving sp2 carbon atoms);The molecule is actually boat shaped and nonaromatic.(Nonaromatic form is more stable than an antiaromatic form)1.46 Å . Aromaticity in higher Annulenes Completely conjugated monocyclic hydrocarbons are called annulenes. Examples The criteria for aromaticity that we discussed earlier can be applied to higher annulenes as well. However, achieving planarity is a hurdle for many larger rings due to potential steric clashes or angle strains. If the ring (with 4n+2 π electrons) is sufficiently large such that planarity does not cause steric or angle strains, the system would adopt that conformation, get stabilization through electron delocalization and become aromatic. Larger annulenes with 4n π electrons are not antiaromatic because they are flexible enough to become non-planar and become non-aromatic.