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-F = C-Cl = C-Br = C-I
- D C-Cl < C-F < C-Br < C-I
Correct answer: A. C-F < C-Cl < C-Br < C-I
Explanation: Bond length increases as the halogen gets larger: C-F is shortest and C-I is longest.
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.