In chemistry, nucleophilic displacement is a type of substitution reaction in which an incoming nucleophile displaces the leaving group. This type of reaction can either be uni- or bimolecular and it may take place with or without the assistance of a base.
Nucleophiles are reagents that have an affinity for electrons, and they react by picking up the electron density from one part of their molecule to another.
They will then donate this electron density to an electrophile as part of a substitution reaction. In order to determine the type of nucleophile that can react with a given electrophile, chemists use what is known as the nucleophilicity scale. This scale ranks different types of nucleophiles in terms of how electron-rich they are, and by extension how effective they will be at displacing other molecules from their chemical bonds.
The most reactive one (nucleophilic) on this chart is hydrogen cyanide (), while the least-reactive ones () include ammonium ion ().
The specific reactions shown below each represent an example where there are two possible products:
One involving substitution via single displacement
Another involving replacement reaction via double bond breakage followed by single bond formation.