Question 12
Explain why the following systems are not aromatic?
(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,
4n + 2 = 4
4n = 2
n = ½
For a compound to be aromatic, the value of n must be an integer (n = 0, 1, 2…), which is not true for the given compound. Hence, it is not aromatic in nature.
(iii) For the given compound, the number of π-electrons is eight. By Huckel's rule,
4n + 2 = 8
4n = 6
n = 3/2
For a compound to be aromatic, the value of n must be an integer (n = 0, 1, 2…). Since the value of n is not an integer, the given compound is not aromatic in nature.
