Final answer:
In SN2 reactions, substrates react faster when they are less sterically hindered, with methyl and primary substrates generally reacting faster than secondary, and tertiary substrates being the least reactive due to steric hindrance.
Step-by-step explanation:
Considering an SN2 reaction, the rate of the reaction is influenced by several factors including the structure of the substrate, the nucleophile, and the solvent. In SN2 reactions, the nucleophile attacks the substrate from the opposite side of the leaving group, displacing it in a single, concerted step.
This reaction mechanism is called bimolecular nucleophilic substitution, or SN2, because the rate-determining step involves two molecules—the nucleophile and the substrate.
The structure of the substrate plays a significant role in the rate of SN2 reactions. The reactivity order for SN2 reactions on different substrates is methyl > primary > secondary > tertiary. Tertiary substrates are generally not reactive in SN2 reactions due to steric hindrance that prevents the nucleophile from approaching the electrophilic carbon (tertiary carbon) effectively.
When comparing SN2 reaction rates, we must therefore look at the degree of substitution at the carbon bearing the leaving group. For example, a primary alkyl halide will generally react faster in an SN2 reaction than a secondary one, and a secondary will generally react faster than a tertiary alkyl halide due to less steric hindrance in the primary and secondary compared to the tertiary.
The correct answer is is: Write the Factors affecting the SN2 Reaction.