Question

Which of the following expressions is representative of the rate law for a $S_{N^2}$ reaction?

• A. Rate = $k$ [electrophile]
• B. Rate = $k$ [electrophile] [nucleophile]
• C. Rate = $k[nucleophile{]}^2$
• D. Rate = $k[electrophile{]}^2$

Answer 1

Answer: (B)

Rate = $k$ [electrophile] [nucleophile]

Nucleophilic substitution reactions which follow second order kinetics are called $S_{N}2$ reactions. The rate of a second-order reaction depends upon the concentrations of the both the reactants.

Thus rate $\alpha$ [electrophile][nucleophile]

or rate = k[electrophile][nucleophile]