Hi Erik, you are correct. That's an excellent catch. Cyclooctatetraene is nonaromatic because it is not fully planar (tub-shaped as you mentioned). It appears to be planar by the standard hybridization argument, but the single bonds can distort the geometry away from planarity making the molecule more stable (because it lacks the increase in energy caused by antiaromaticity). I was unaware of this. The main takeaway is to be wary of the sigma bonds in larger cyclic structures. They may adopt a nonplanar structure (due to carbon-carbon bond rotation) which is more stable. Thank you for bringing this to my attention!
Helpful really
Thank you! Question though, isn't
Cyclooctatetraene in question 5 tub-shaped and thus non-aromatic?
Hi Erik, you are correct. That's an excellent catch. Cyclooctatetraene is nonaromatic because it is not fully planar (tub-shaped as you mentioned). It appears to be planar by the standard hybridization argument, but the single bonds can distort the geometry away from planarity making the molecule more stable (because it lacks the increase in energy caused by antiaromaticity). I was unaware of this. The main takeaway is to be wary of the sigma bonds in larger cyclic structures. They may adopt a nonplanar structure (due to carbon-carbon bond rotation) which is more stable. Thank you for bringing this to my attention!
@@chemtutorderek870 Thank you! Good to know and thanks for the excellent description, a great help for exams.