JEE Chemistry 2025 Question with Solution

Given: Four halides are provided, and we must identify which one generates the most stable carbocation in a nucleophilic substitution reaction.

Find: The option that forms the carbocation with the greatest stability.

Carbocation stability depends mainly on delocalization and resonance stabilization.

From the solution text:

• the carbocation generated from option (4) is the most stable,
• because it is stabilized by resonance involving the phenyl rings,
• whereas the carbocations from options (1), (2), and (3) have less stabilization.

Thus, the halide in option D forms the most stable carbocation.

Therefore, the correct option is D.

Given: Stability of the intermediate carbocation determines which halide is favored for substitution through carbocation formation.

Find: Which structure gives the most stabilized carbocation after loss of $\text{Br}^-$.

A carbocation becomes especially stable when its positive charge can be delocalized by resonance.

Option D corresponds to a highly resonance-stabilized carbocation because the positively charged carbon is attached to phenyl groups, allowing extensive delocalization of charge into the aromatic rings.

The other options do not provide comparable resonance stabilization.

Therefore, the most stable carbocation is obtained from option D.