The rate of an SN1 reaction depends on the concentration of

  • A. both the alkyl halide and the nucleophile
  • B. the alkyl halide only
  • C. the nucleophile only
  • D. the solvent only

Explanation

The slow, rate determining step is the ionisation of the alkyl halide into a carbocation and a halide ion, and the nucleophile is not involved until the fast second step, so it does not appear in the rate equation. This is why the reaction is called unimolecular. Detecting first order kinetics is the standard experimental evidence for the SN1 pathway.

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