Question

Which of the following halides will be most reactive in $S_{N}2$ reaction and $S_{N}1$ reaction, respectively?

• A. I, II
• B. II, I
• C. I, III
• D. III, I

Answer 1

The correct option is C

I, III

(I) $\Rightarrow 1^{\circ }$ Allylic halide and less steric hindrance, hence $S_{N}2$.

(III) $\Rightarrow 3^{\circ }$ Allylic halide, most stable carbocation ion and hence $S_{N}1$.