Question

Which one is most reactive towards S_N1 reaction?

Options

• C₆H₅CH(C₆H₅)Br

• C₆H₅CH(CH₃)Br

• C₆H₅C(CH₃)(C₆H₅)Br

• C₆H₅CH₂Br

Answer 1

C₆H₅C(CH₃)(C₆H₅)Br

Explanation:

As we know that S_N1 reaction proceeds via formation of a carbocation intermediate.

Thus, the more stable the carbocation, the more reactive the aryl halide is toward the S_N1 reaction.

Here in this compound, +I effect of −CH₃ and delocalisation of +ve charge over the two phenyl rings reduce the magnitude of the positive charge on the carbon atom, making it the most stable carbocation.

Hence,

will undergo S_N1 faster.