JEE Chemistry 2025 Question with Solution

Given: Four carbocations are shown.

Find: The most stable carbocation.

Carbocation stability increases when the positive charge is stabilized by resonance. A methoxy group $\text{-OCH}_3$ donates electron density by resonance, while a methyl group mainly provides weaker hyperconjugative or inductive effects.

From the solution, the benzylic carbocation with the most effective resonance stabilization is the structure corresponding to option D.

Therefore, the correct option is D.

Given: The structures differ by substituents on the benzene ring attached to a benzylic carbocation.

Find: Which substituted benzylic carbocation is most stable.

The solution states that carbocation stability depends on substitution, hyperconjugation, and especially resonance.

• Primary carbocations are less stable.
• Secondary carbocations are more stable than primary carbocations.
• Tertiary carbocations are more stable due to greater hyperconjugation.
• Resonance-stabilized carbocations can be more stable because the positive charge is delocalized.

Among the given structures, the methoxy-substituted benzylic carbocation is identified in the solution as the most resonance-stabilized species.

Hence, the most stable carbocation is option D.