Answer: C-F > C-Cl > C-Br > C-I.
- A C-F > C-Cl > C-Br > C-I
- B C-I > C-Br > C-Cl > C-F
- C C-Cl > C-F > C-Br > C-I
- D C-Br > C-I > C-F > C-Cl
Correct answer: A. C-F > C-Cl > C-Br > C-I
Explanation: Bond strength decreases as the halogen gets larger and its orbitals overlap less effectively with carbon: C-F is strongest and C-I is weakest.
SN2 proceeds in a single step with backside attack and inversion of configuration, while SN1 forms a planar carbocation intermediate first, leading to racemisation.
Concept context
Study carbon-halogen compounds: how they are made, how they react via SN1/SN2 and elimination, their stereochemistry, and their environmental impact.