SN1 vs SN2 Reactions

Substitution Nucleophilic (SN) reactions are a fundamental part of organic chemistry. In this topic, we will explore the differences between SN1 and SN2 mechanisms, their stereochemistry, and the factors that influence them.

SN1 (Substitution Nucleophilic Unimolecular)

• Kinetics: 1st order (Rate = k[Substrate]).
• Mechanism: Two-step process forming a carbocation intermediate.
• Stereochemistry: Racemization (both retention and inversion).
• Substrate Reactivity: 3° > 2° > 1° > CH3X (due to carbocation stability).

SN2 (Substitution Nucleophilic Bimolecular)

• Kinetics: 2nd order (Rate = k[Substrate][Nucleophile]).
• Mechanism: Single-step concerted process without an intermediate.
• Stereochemistry: Complete inversion of configuration (Walden inversion).
• Substrate Reactivity: CH3X > 1° > 2° > 3° (due to steric hindrance).