Substitution Reaction
A reaction in which one atom or group in a molecule is replaced by another.
Formula / equation
R–X + Y → R–Y + X
Unit
Dimensionless
In depth
Substitution is the dominant mode for saturated compounds and aromatic rings, which have no pi bond available for addition. It proceeds by nucleophilic, electrophilic or free-radical pathways depending on the substrate and the attacking species, and each pathway has its own characteristic kinetics.
Examples in the real world
CH₄ + Cl₂ → CH₃Cl + HCl under UV light; the nitration of benzene to nitrobenzene.