Question

Which of the following compound is not aromatic?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

(a) 1,3-cyclobutadiene is a cyclic, planar conjugated molecule having 4 $\pi$-electrons. Therefore, it is not an aromatic compound.

(b)
Pyridine is a cyclic, planar conjugated molecule having 6 $\pi$-electrons. Therefore, it is an aromatic compound.
(Here lone pair of electrons of $N$ are not involved in delocalisation.)

(c)
Furan is a cyclic, planar conjugated molecule having 6 $\pi$-electrons. Therefore, it is an aromatic compound.

(d)
Thiophene is a cyclic, planar conjugated molecule having 6 $\pi$-electrons. Therefore, it is an aromatic compound.

Hence option (a) is correct.