3
$\begingroup$

I have read that, cycloprop-2-ene-1-one is aromatic and cyclopent-2,4-dien-1-one is antiaromatic. Basically this is visualized by visualizing the resonance structures of this.

enter image description here

Similarly if I apply this concept in para benzoquinone, I get that it is antiaromatic because of 4 conjugated $\pi$ electrons. But many sites on net say it is not aromatic. Where am I going wrong ?

$\endgroup$
2
  • $\begingroup$ The concept is called resonance and the contributing structures are called resonance structures; they are not called resonating structures. $\endgroup$ Sep 11 at 8:14
  • $\begingroup$ link does this clears your doubt? $\endgroup$ Sep 11 at 11:20
2
$\begingroup$

Para-benzoquinone is antiaromatic, and tries to get out of antiaromaticity by disrupting the conjugation; i.e. lengthening the "single bonds" so that pi-overlap across these bonds is not very feasible. This effectively results in two seperate pi-bonds in the ring; hence the observed "non-aromaticity".

It does have antiaromatic characters though, in the sense that it is a strong oxidant, easily taking away two electrons from other molecules so that it can become the aromatic(6pi) hydroquinone diide anion.

$\endgroup$
1
  • $\begingroup$ Antiaromaticity is a purely hypothetical concept, such compounds cannot exist. By distorting the structure the symmetry of the molecule is reduced, therefore breaking degeneracy. A small distortion can lead to a significant change there, while overlap will probably be still very similar. $\endgroup$ Sep 11 at 8:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.