Which among the following halides will generate the most stable carbocation in Nucleophillic substitution reaction?
(A)(see structure)
(B)(see structure)
(C)(see structure)
(D)(see structure)✓ Correct
Answer: (D)
Solution
Carbocation stability rises with the extent of charge delocalization available to it. A simple allylic cation delocalizes over one double bond, and a mono-benzylic secondary cation delocalizes into one aromatic ring, but a diphenylmethyl cation, Ph2C+H, places the positive charge in conjugation with two benzene rings simultaneously. This dual resonance stabilization spreads the charge far more effectively than a single ring or a single alkene can, making the diphenylmethyl cation the most stable of the four, and its precursor halide the one that generates a carbocation most readily in nucleophilic substitution.
JEE Main · 2025 · 29 Jan 2025 · Shift 2 · Single correct option
