Addition reaction

Addition of chlorine to ethylene

An addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one .

Addition reactions are limited to chemical compounds that have multiply-bonded atoms, such as molecules with carbon-carbon double bonds, i.e., alkenes, or with triple bonds, i.e., alkynes. Also included are molecules containing carbon - hetero double bonds like those with carbonyl (C=O) groups or those with imine (C=N) groups.

There are two main types of polar addition reactions electrophilic addition and nucleophilic addition One non-polar addition reaction exists as well called free radical addition.

Addition reactions general overview. Top to bottom: electrophic addition to alkene, nucleophilic addition of nucleophile to carbonyl and free radical addition of halide to alkene

An addition reaction is the opposite of an elimination reaction. For instance the hydration reaction of an alkene and the dehydration of an alcohol are addition-elimination pairs. Addition reactions are also encountered in polymerizations and called addition polymerization.

Addition-elimination reaction

In the related Addition-elimination reaction an addition reaction is followed by an elimination reaction. In the majority of reactions it involves addition of nucleophiles to carbonyl compounds in what is called nucleophilic acyl substitution .

Other addition-elimination reactions are the reaction of an aliphatic amine to an imine and an aromatic amine to a Schiff base in alkylimino-de-oxo-bisubstitution. The hydrolysis of nitriles to carboxylic acids is also a form of addition-elimination.