Illustrated Glossary of Organic Chemistry

Nucleophile (Nuc): A reactant that provides a pair of electrons to form a new covalent bond (i.e. a Lewis base). A nucleophile that shares an electron pair with a proton is usually called a Bronsted-Lowry base, or just a base.

Hydroxide ion as a nucleophile in an S_N2 reaction.


Chloride ion as a nucleophile in an S_N1 reaction.