JEE Chemistry 2025 Question with Solution

Given: Species $p$, $q$ and $r$ are to be compared for stability.

Find: The correct stability order.

The solution identifies stability using aromaticity, anti-aromaticity and resonance.

1. Species $p$ is cyclopropenyl anion. It has $4\pi$ electrons, so it is anti-aromatic and therefore highly unstable.
2. Species $q$ is cyclopentadienyl anion. It has $6\pi$ electrons, so it follows Hückel's rule $(4n+2)\pi$ and is aromatic, making it highly stable.
3. Species $r$ is treated as more stable than the anti-aromatic species, but less stable than the aromatic species, due to relative resonance considerations.

Hence, the stability order is: $q > r > p$ Therefore, the correct option is A.

Given: The three species/molecules $p$, $q$ and $r$ shown in the figure.

Find: Their decreasing order of stability.

Key idea: Aromatic compounds are especially stable because of cyclic conjugation and delocalized $\pi$ electrons satisfying Hückel's rule. Anti-aromatic compounds are destabilized, while non-aromatic compounds do not gain special aromatic stabilization.

From the extracted solution:

• $p$ is anti-aromatic with $4\pi$ electrons.
• $q$ is aromatic with $6\pi$ electrons.
• $r$ is placed between $q$ and $p$ in stability.

So the final order is: $q > r > p$ Thus, the correct answer is A.