Answer: Only substrate concentration.
- A Both substrate and nucleophile concentration
- B Only nucleophile concentration
- C Only substrate concentration
- D Temperature only
Correct answer: C. Only substrate concentration
Explanation: SN1 is a two-step reaction; the slow step is formation of the carbocation (involves only the substrate), so rate = k[substrate].
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.