Question

Question 13.12 Explain why the following systems are not aromatic?

(i)


(ii)


(iii)

Class XI Hydrocarbons Page 397

Answer 1

conditions of aromaticity are :
1. it should be planer. means all carbon atoms are sp² hybridized .
2. it contains (4n + 2) π electrons .


(i) This molecule is not a planar molecule because of the presence of one sp³ hybridized carbon atom. it contains six π-electrons = (4×1+2)π electrons , follow huckel number of electrons but it's π- electron cloud doesn't surround all the carbon atoms of the rings .
that's why it is non - aromatic compound.


(ii) This is not planar because of the presence of one sp³ hybridized carbon atom. moreover , it contains only 4π electrons ≠ (4n + 2)π electrons , doesn't follow the Hukel's number of electrons. Thus, the molecule is not aromatic . hence, it is non- aromatic compound.

(iii) this molecule is non- aromatic because of the 8π electrons ≠(4n + 2)π electrons . also it doesn't a planar compound( because it is like tub-shaped ). hence, it is non - aromatic compound .