Which of the following halides will react most rapidly in a SN2 reaction?

Which of the following halides will react most rapidly in a SN2 reaction?

Explanation
  • SN2 reactions favor weaker C-X bonds, and iodine (I) has the weakest bond due to its large atomic size.
  • CH₃I reacts fastest because iodide is a better leaving group than Br, Cl, or F.