Question

Which of the following will undergo a faster $S_{N}2$?

• A. I
• B. Neither I nor II
• C. Both undergo $S_{N}2$ at the same rate
• D. II

Answer 1

The correct option is D

II

For $S_{N}2$, the ideal substrates are primary or methyl halides (X = Cl, Br, I). Both have the same carbon skeleton. So the faster $S_{N}2$ will depend on the ability of the leaving group. Iodide is a much better leaving group than Chloride. Hence II.