Stereochemistry of S N 2 Reaction Inversion of Configuration
Proof of Inversion of Configuration at a Chiral Center
Acetate Approaches from 180 o Behind Leaving Group
Inversion on a Ring is often more Obvious: Cis Trans
Substrate Reactivity Since the energy of the transition state is significant in determining the rate of the reaction, a primary substrate will react more rapidly than secondary (which is much more rapid than tertiary).
Hammond’s Postulate Related species that are close in energy are close in structure. In an endothermic reaction, the transition state is similar to the product in structure and stability. In an exothermic reaction, the transition state is similar to the reactant in structure and stability. i.e. the structure of the transition state resembles the structure of the most stable species.
Endo- transition state looks like product Exo- transition state looks like reactant