(a) Addition reaction
- Occurs when two reactants react to form one product.
- Involves compounds with multiple bonds (unsaturated). The reaction results in breaking of one pi (π) bond to form two sigma (σ) bonds.
(b) Substitution reaction
- Involves replacing one atom or group with another.
(c) Elimination reaction
- Involves the elimination of two neighbouring atoms from saturated molecules, with the formation of multiple bonds.
- The reverse of addition reaction.
- Occurs at the transition stage of a reaction involving carbocation.
- Occurs when a single reactant reorganises the bonds or atoms.