question_answer 1)

Explain why the following systems are not aromatic? (i) (ii) (iii)  

Answer:

(i) Due to the presence of \[s{{p}^{3}}\] -hybridized carbon, the system is not planar. It contains six \[\pi \]-electrons but the system is not fully conjugated since all the six \[\pi \]-electrons do not form a single cyclic electron cloud. Therefore, it is not an aromatic compound. (ii) \[(4n+2)\]\[\pi \] -electron (Huckels rule) is not applicable. It contains only four electrons and dueto the presence of a \[s{{p}^{3}}\] -carbon, the system is not planar. Therefore, the system is not aromatic. (iii) It is a non-planar system having eight \[\pi \]-electrons. It does not contain a planar cyclic cloud having \[(4n+2)\]\[\pi \]-electrons. Therefore, the molecule is not aromatic.