Which of the followig is not aromatic?

Options

A.
B.
C.
D.

Answer

4

Explanation

In compound (1), each N has alone pair of electrons providing a total of six `e^(-)s` and an empty p orbital on each B can overlap with any of the adjacent N atoms. Thus, thecompound has `6pi` delocalized `e^(-)s` Similarly in compound (2), the empty p orbital on B can overlap with any of the adjacent p atomic orbital on C atoms giving `6pi` delocalized `e^(-)s` in compound (4), similar overlap is possible but the number of `pie^(-)s` is only four which is not Hyckel number.