nucleophilic substitution

Nucleophilic substitution is a type of chemical reaction where an atom, ion, or group within a molecule is replaced by another. In this process, a nucleophile, which is an electron-rich species, attacks a substrate molecule. The nucleophile provides the electron pair to form a new bond with the substrate, displacing an existing atom or group, known as the leaving group.1

A common mechanism for nucleophilic substitution at saturated carbon centers is the bimolecular mechanism. In this process, the nucleophile approaches the substrate from one side while the leaving group departs from the opposite side. This results in an inversion of the molecule's stereochemical configuration, much like an umbrella turning inside out. This reaction is considered synchronized, as the nucleophile's entry and the leaving group's departure happen simultaneously. The reaction rate typically depends on the concentrations of both the substrate and the nucleophile.2