Which of the following compounds is aromatic?

From the 4n+2 rule, it must be either option 2 or 4. The answer given in my book is option 4. Why? I think It might be due to one being planar and the other not, but to me both seem to be planar. Is there a way to check if one is planar or not?


1 Answer 1


Number 2 is not aromatic because transannular $\ce{C-H}$ interactions cause the molecule to be non-planar although it satisfies $4n+2$. This problem was solved by the synthesis of number 4, which, while a little less than planar but rigid, displays aromatic properties (NMR, etc., Ref 1).


  1. E. Vogel, H. D. Roth, "The Cyclodecapentaene System," Angew. Chem. Int'l. Ed. 1964, 3(3), 228-229 (DOI: https://doi.org/10.1002/anie.196402282).
  • 2
    $\begingroup$ Yeah, there was also analogous ether IIRC. $\endgroup$
    – Mithoron
    Dec 13, 2017 at 0:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

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