question_answer

Which one of the following is not aromatic?

A)  Cyclopentadienyl anion

B)  Cycloheptatrienyl cation

C)  Cyclooctatetraene

D)  Thiophene

Correct Answer: C

Solution :

 Cyclooctatetraene is not aromatic in nature. In cyclooctatetraene, delocalisation of\[\pi -\]electrons takes place but HuckeFs rule is not followed. According to HuckeFs rule, it should contains\[10\pi (4n+2)\] electrons but it contains only \[8\pi \] electrons. \[\pi \]electron \[(8)\ne (4n+2)=10\] (i.e., Huckel rule is not followed), hence it is not aromatic.