Question

Which of the following compound readily undergo both $S_{N}1$ and $S_{N}2$ reaction?

• A.
• B.
• C.
• D. None of the above

Answer 1

The correct option is B

(a) is primary alkyl halide which forms unstable carbocation so it does not undergo $S_{N}1$ reaction.

(c) has a large steric hindrance so back attack of nucleophile is difficult hence, it does not under $S_{N}2$ reaction.

Benzylic and allylic halides may undergo both $S_{N}1$ and $S{N}_2$ reactions.

Benzylic and allylic halides undergo $S_{N}1$ due to the formation of stable carbocation.

Benzylic and allylic halides undergo $S_{N}2$ because the electron deficient transition state is stabilised by the $\pi$ system in the molecule.