Question

Which out of the following is aromatic hydrocarbon?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

It is a trick question that explicitly refers to "hydrocarbon." (B) and (D) are also aromatic but they are not hydrocarbons as they contain heteroatoms (O & N) respectively.

For a monocyclic compound to be aromatic, all the members of the cycle need to be planar - in most cases, $s{p}^2$ hybridized. Further, each atom of the ring should also have an empty pure-p orbital such that overall there are $4n+2$ electrons forming a delocalized electron cloud. Naphthalene clearly fits the bill here.

Cyclobutadiene is antiaromatic. It is not even stable and is incredibly hard to isolate.