In an SN2 reaction, which statement correctly describes the mechanism?

In an SN2 reaction, which statement correctly describes the mechanism?

• A. It proceeds via a carbocation intermediate.
• B. It proceeds via a concerted mechanism with backside attack and inversion.
• C. It requires a radical chain mechanism.
• D. It is a purely elimination process.

Answer: (C)

SN2 reactions proceed through a single, concerted step where the nucleophile attacks the carbon from the backside as the leaving group leaves. This backside approach creates a transition state in which new and old bonds are in the process of forming and breaking, and the stereochemistry at the carbon is inverted (Walden inversion). There is no discrete carbocation intermediate formed, so SN2 is not the same as an SN1 mechanism. It also does not rely on radical chemistry or a radical chain process, which would involve different reactive intermediates. Additionally, SN2 is not an elimination process; elimination pathways (like E2) remove atoms to form a double bond, whereas SN2 results in substitution by the nucleophile. The rate law reflects this bimolecular nature: the rate depends on both the substrate and the nucleophile, highlighting the concerted, one-step mechanism.

SN2 reactions proceed through a single, concerted step where the nucleophile attacks the carbon from the backside as the leaving group leaves. This backside approach creates a transition state in which new and old bonds are in the process of forming and breaking, and the stereochemistry at the carbon is inverted (Walden inversion). There is no discrete carbocation intermediate formed, so SN2 is not the same as an SN1 mechanism. It also does not rely on radical chemistry or a radical chain process, which would involve different reactive intermediates. Additionally, SN2 is not an elimination process; elimination pathways (like E2) remove atoms to form a double bond, whereas SN2 results in substitution by the nucleophile. The rate law reflects this bimolecular nature: the rate depends on both the substrate and the nucleophile, highlighting the concerted, one-step mechanism.