Question

On the basis of molecular orbital treatment of various aromatic compounds, it has been observed that an aromatic compound must fulfill 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 p-orbital 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 an odd number of pair of $\pi$ - electrons , $(4n+2)\pi$ - electrons, where n is an integer. Which of the following structures is not
aromatic?

• A. I& II
• B. II&IV
• C. IV
• D. All the four

Answer 1

The correct option is D All the four

All given compounds contain 4n pi electrons so they all are not aromatic. For aromatic, the compound should have (4n+2) pi electrons. But none of them have this much of electron in their molecule.