* Expected Aromaticity: Cyclooctatetraene has 8 pi electrons, which seems like a Hückel number (4n+2, where n=2). This would suggest it should be aromatic.
* Planarity Issue: A key requirement for aromaticity is planarity. However, cyclooctatetraene is non-planar due to its tendency to adopt a tub-shaped conformation. This non-planar structure prevents effective pi electron delocalization across the ring.
* Resonance Energy: Due to its non-aromatic nature, cyclooctatetraene has negligible resonance energy.
What does this mean?
* It means the molecule is not particularly stable due to the lack of resonance stabilization.
* It behaves more like a typical alkene, with localized double bonds.
In summary: Cyclooctatetraene's resonance energy is negligible because it doesn't have the necessary planarity for effective pi electron delocalization and aromaticity.
