Answer: 1° > 2° > 3°.
- A 3° > 2° > 1°
- B 1° > 2° > 3°
- C 2° > 1° > 3°
- D All are equal
Correct answer: B. 1° > 2° > 3°
Explanation: SN2 is hindered by steric bulk; primary haloalkanes have the least steric hindrance so they react fastest in SN2.
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.