Question

On the basis of molecular orbital treatment of various aromatic compounds , it has been observed that an aromatic compound must fulfil the following theoretical requirements.a) It must have an uninterrupted cyclic cloud of $\pi$ - electrons above and below the plane of the molecule ( often called as $\pi$ - cloud). Let us look what does this mean?
i) For the $\pi$ - cloud to be cyclic, the molecule must be cyclic.
ii) For the $\pi$ - cloud to be uninterrupted, every atom in the ring must have a p- orbital. iii) For the $\pi$ -cloud to be formed ,each porbital must be able to overlap with the p-orbitals on either side of it. Therefore, the molecule must be planar .
b) The $\pi$ - cloud must contain and odd number of pair of $\pi$ - electrons , $(4n+2)\pi$- electrons, where n is an integer.
Cyclo- octatetraene is:

• A. aromatic
• B. non - aromatic due to (a) (ii)
• C. non- aromatic due to (a) (iii)
• D. non- aromatic due to (b)

Answer 1

The correct option is D non- aromatic due to (b)

As cyclo- octatetraene contains 8 $\pi$ electrons so it doesnt contain $(4n+2)\pi$- electrons.
So it is non aromatic.