An addition reaction, in organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

, is in its simplest terms an organic reaction

Organic reaction

Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...

 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 bond

Double bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

s, i.e., alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

s, or with triple bond

Triple bond

A triple bond in chemistry is a chemical bond between two chemical elements involving six bonding electrons instead of the usual two in a covalent single bond. The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are...

s, i.e., alkyne

Alkyne

Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature...

s. Also included are molecules containing carbon—hetero double bonds like those with carbonyl

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....

 (C=O) groups or those with imine

Imine

An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base...

 (C=N) groups.

There are two main types of polar addition reactions: electrophilic addition

Electrophilic addition

In organic chemistry, an electrophilic addition reaction is an addition reaction where, in a chemical compound, a π bond is broken and two new σ bonds are formed...

 and nucleophilic addition

Nucleophilic addition

In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a π bond is removed by the creation of two new covalent bonds by the addition of a nucleophile....

. Two non-polar addition reaction exists as well called free radical addition

Free radical addition

Free radical addition is an addition reaction in organic chemistry involving free radicals. The addition may occur between a radical and a non-radical, or between two radicals....

 and cycloaddition

Cycloaddition

A cycloaddition is a pericyclic chemical reaction, in which "two or more unsaturated molecules combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity." The resulting reaction is a cyclization reaction.Cycloadditions are usually described by the...

s.
An addition reaction is the opposite of an elimination reaction

Elimination reaction

An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism...

. For instance the hydration reaction

Hydration reaction

In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group and a hydrogen cation are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous...

 of an alkene

Alkene

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...

 and the dehydration of an alcohol

Alcohol

In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 are addition-elimination pairs. Addition reactions are also encountered in polymerizations and called addition polymerization

Addition polymerization

Chain growth polymerization is a polymerization technique where unsaturated monomer molecules add on to a growing polymer chain one at a time...

.

Addition-elimination reaction

In the related Addition-elimination reaction an addition reaction is followed by an elimination reaction

Elimination reaction

An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism...

. In the majority of reactions it involves addition of poti to carbonyl compounds in what is called nucleophilic acyl substitution

Nucleophilic acyl substitution

Nucleophilic acyl substitution describes the substitution reaction involving nucleophiles and acyl compounds. Acyl compounds are carboxylic acid derivatives including esters, amides and acid halides...

.

Other addition-elimination reactions are the reaction of an aliphatic amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

 to an imine

Imine

An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base...

 and an aromatic amine to a Schiff base

Schiff base

A Schiff base, named after Hugo Schiff, is a compound with a functional group that contains a carbon-nitrogen double bond with the nitrogen atom connected to an aryl or alkyl group, not hydrogen....

 in alkylimino-de-oxo-bisubstitution

Alkylimino-de-oxo-bisubstitution

Alkylimino-de-oxo-bisubstitution in organic chemistry is the organic reaction of carbonyl compounds with amines to imines . The reaction name is based on the IUPAC Nomenclature for Transformations...

. The hydrolysis of nitrile

Nitrile

A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...

s to carboxylic acid

Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

s is also a form of addition-elimination.