Explain why the following systems are not aromatic?
Question:

Explain why the following systems are not aromatic?

(i)

(ii)

(iii)

Solution:

(i)

For the given compound, the number of π-electrons is six. But only four π-electrons are present within the ring. Also there is no conjugation of π-electrons within the ring and the compound is not planar in shape. Hence, the given compound is not aromatic in nature.

(ii)

For the given compound, the number of π-electrons is four.

By Huckel’s rule,

$4 n+2=4$

$4 n=2$

$n=\frac{1}{2}$

For a compound to be aromatic, the value of must be an integer (= 0, 1, 2…), which is not true for the given compound. Hence, it is not aromatic in nature.

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