What is the Difference Between SN1 and SN2 Reactions?

The main difference between SN1 and SN2 reactions lies in the timing of the bond-forming and bond-breaking steps. Both reactions are nucleophilic substitution reactions, but they proceed through different mechanisms:

SN1 Reaction

• Unimolecular reaction
• Two-step mechanism
• Carbocation is formed as an intermediate part of the reaction
• Favored by weak nucleophiles, primary and secondary alkyl halides, and polar protic solvents
• Results in a mixture of R and S products due to the planar nature of the carbocation and attack from either side

SN2 Reaction

• Bimolecular reaction
• One-step mechanism
• No carbocation is formed during the reaction
• Favored by strong nucleophiles, methyl and primary alkyl halides, and polar aprotic solvents
• Results in inversion of configuration, as the nucleophile and leaving group are on opposite sides of the carbon

In summary, SN1 reactions involve a sequential two-step process, forming a carbocation intermediate, while SN2 reactions involve a single concerted step with no carbocation formation. The factors that favor each reaction, such as nucleophile strength, substrate structure, and solvent properties, also differ.

Comparative Table: SN1 vs SN2 Reactions

Here is a table comparing the differences between SN1 and SN2 reactions:

SN1 and SN2 reactions are both nucleophilic substitution reactions, but they differ in their mechanisms, rate-determining steps, rate laws, nucleophiles, and stereochemistry.