SN2 Reaction
A single-step nucleophilic substitution in which bond formation and bond breaking occur simultaneously.
Formula / equation
rate = k[substrate][nucleophile]
Unit
L/(mol·s)
In depth
The nucleophile attacks from the side opposite the leaving group, passing through a trigonal bipyramidal transition state and inverting the configuration at carbon. Steric hindrance is decisive, so rate falls sharply from methyl through primary to secondary, and tertiary substrates do not react.
Examples in the real world
Bromomethane with hydroxide; the Walden inversion converting one enantiomer cleanly into the other.