Addition Reaction
A reaction in which two molecules combine to form a single larger product, with no atoms left over.
Formula / equation
A + B → AB
Unit
Dimensionless
In depth
Addition is characteristic of unsaturated compounds, where a pi bond is broken and two new sigma bonds are formed, always making the product more stable. Because nothing is eliminated, addition reactions are perfectly atom-economical, which is why they are preferred in green synthesis.
Examples in the real world
CH₂=CH₂ + Br₂ → CH₂BrCH₂Br, decolourising bromine water as the test for unsaturation.