Question

Which of the following statements best describes the relative rates of SN2 and E2 reactions?

A. The rates are equal because they are both bimolecular.

B. The relative rates of each depends only of the steric hinderance of the substrate and the nucleophile.

C. The relative rates of each depends on only the steric hinderance of the substrate and the nucleophile's ability to reach the antibonding orbital.

D. The relative rates are described by the probability of the nucleophle acting as a Lewis base relative to the probability of acting as a Bronsted-Lowry base.

E. No direct comparison can be made.

The answer key says D, but I don't understand why.

Answer 1

Ans D) The relative rates are described by the probability of the nucleophile acting as a lewis base relative to the probability of acting as a Bronsted Lowry base

Both SN2 and E2 reactions are bimolecular reactions , as their names suggest. These reactions occur in single step , and are hindered by the steric hinderance of the compound. So the relative rates of these reactions depend on their nucleophile that acts as a lewis base to donate its pair of electrons relative to acceptance of proton.