Illustrated Glossary of Organic Chemistry

Nucleophilic substitution: A substitution reaction in which the new group introduced into the molecule was a nucleophile in the reaction mechanism.

This S_N2 reaction is a nucleophilic substitution reaction. The new group (iodide ion; in red) was a nucleophile.


This S_N1 reaction is a nucleophilic substitution reaction. The new hydroxyl group is installed when the carbocation bonds to a nucleophile (water; in red).


This substitution reaction example is an electrophilic substitution reaction and not a nucleophilic substitution reaction because the new nitro group was installed when ⁺NO₂ (an electrophile; in blue) bonded with the benzene ring.