Question

Cyclobutadiene is said to be :

• A. aromatic
• B. aliphatic
• C. anti-aromatic
• D. none of the above

Answer 1

The correct option is C anti-aromatic

According to Huckel's rule, if a cyclic, planar molecule has $(4n+2)$ $\pi$ electrons, it is considered to be aromatic.

Aliphatic compounds are chemical compounds belonging to the organic class in which the atoms are not linked together to form a ring. They are non-aromatic compounds.

Antiaromaticity is a characteristic of a cyclic molecule with a π electron system that has higher energy due to the presence of $4n\pi$ electrons in it.

Unlike aromatic compounds, which follow Hückel's rule ($[4n+2]\pi$ electrons) and are highly stable, antiaromatic compounds are highly unstable and highly reactive.

So, cyclobutadiene is anti-aromatic as it has $4$$\pi$ electrons. (Cyclic, planar)

Option C is correct.