Chemistry - GOC Question with Solution | TestHub

Question Explanation:

The question asks to identify which cyclic organic molecules are unstable at room temperature, specifically due to anti-aromaticity.

Concept:

This question is based on aromaticity, anti-aromaticity and Hückel's rule.

Solution:

Anti-aromatic compounds are planar, cyclic, fully conjugated systems with 4n pi electrons and are highly unstable at room temperature.

(2) Cyclobutadiene is anti-aromatic (4pi electrons, $\mathrm{n}=1$ ) and unstable.

(3) Cyclopentadienone is also anti-aromatic and unstable, acting as a 4pi electron system due to $\mathrm{C}=\mathrm{O}$ bond polarization.

Molecule (1) is non planar, non-aromatic and molecule (4) is aromatic and both are stable.