Which of the following compound is not aromatic?
In the option A ) cycloheptatrienyl anion has 8 pi electrons. Thus the number of pi electrons in cycloheptatrienyl anion is not equal to 2,6,10, 14 Hence, cycloheptatrienyl anion is not an aromatic compound. Hence, the correct option is option A ).
Can heterocycles be aromatic?
Heterocycles cyclic structures in which the ring atoms may include oxygen or nitrogen can also be aromatic. Pyridine, for example, is an aromatic heterocycle.