What is the rate equation for an SN2 reaction?

In an SN2 reaction, the mechanism involves a nucleophile (Nu) attacking the electrophile (R-L), which is a substrate with a leaving group. The key characteristic of SN2 reactions is that they occur in a single concerted step where the nucleophile and the substrate interact directly, leading to the simultaneous bond formation and bond breaking.

The rate of an SN2 reaction is dependent on the concentrations of both the nucleophile and the substrate, as the reaction involves both species participating in the transition state. Therefore, the rate equation can be expressed as the product of the concentration of the nucleophile and the concentration of the substrate, multiplied by the rate constant (k), which is intrinsic to the reaction's conditions.

This rate law reflects the second-order nature of the reaction since it depends on two reactants, hence the rate equation is formulated as: rate = k[Nu][R-L]. This aligns perfectly with the properties of SN2 reactions, making option C the accurate description of the rate law for this type of reaction.