Amination
Encyclopedia
Amination is the process by which an amine
group is introduced into an organic molecule
. Enzymes which catalyse
this reaction, are termed aminases. This can occur in a number of ways including reaction with ammonia
or another amine
such as an alkylation
, reductive amination
and the Mannich reaction
. For example, -COOH --> -CONH2.
Alkylation is the addition of an alkyl group where acylation is the addition of an acyl
group (-COCH3). Acylation has two steps; Acylation (the addition of an acylium ion) and then reduction. Reduction can often happen more than once.
and the organic compound as the electrophile
. However, this sense of reactivity may be reversed for some electron-deficient amines, including oxaziridine
s, hydroxylamine
s, oxime
s, and other N–O substrates. When the amine is used as an electrophile
, the reaction is called electrophilic amination. Electron-rich organic substrates that may be used as nucleophiles for this process include carbanion
s and enolates.
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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
group is introduced into an organic molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
. Enzymes which catalyse
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
this reaction, are termed aminases. This can occur in a number of ways including reaction with ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
or another 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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
such as an alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
, reductive amination
Reductive amination
Reductive amination is a form of amination that involves the conversion of a carbonyl group to an amine via an intermediate imine...
and the Mannich reaction
Mannich reaction
The Mannich reaction is an organic reaction which consists of an amino alkylation of an acidic proton placed next to a carbonyl functional group with formaldehyde and ammonia or any primary or secondary amine. The final product is a β-amino-carbonyl compound also known as a Mannich base...
. For example, -COOH --> -CONH2.
Alkylation is the addition of an alkyl group where acylation is the addition of an acyl
Acyl
An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids.In organic chemistry, the acyl group is usually derived from a carboxylic acid . Therefore, it has the formula RCO-, where R represents an alkyl group that is...
group (-COCH3). Acylation has two steps; Acylation (the addition of an acylium ion) and then reduction. Reduction can often happen more than once.
Electrophilic Amination
Most commonly, amination reactions involve the use of the amine as the nucleophileNucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
and the organic compound as the electrophile
Electrophile
In general electrophiles are positively charged species that are attracted to an electron rich centre. In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile...
. However, this sense of reactivity may be reversed for some electron-deficient amines, including oxaziridine
Oxaziridine
An oxaziridine is an organic molecule that features a three-membered heterocycle containing oxygen, nitrogen, and carbon.-History:Oxaziridine derivatives were first synthesized in the mid 1950s by Emmons and subsequently by Krimm and Horner and Jürgens...
s, hydroxylamine
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
s, oxime
Oxime
An oxime is a chemical compound belonging to the imines, with the general formula R1R2C=NOH, where R1 is an organic side chain and R2 may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds...
s, and other N–O substrates. When the amine is used as an electrophile
Electrophile
In general electrophiles are positively charged species that are attracted to an electron rich centre. In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile...
, the reaction is called electrophilic amination. Electron-rich organic substrates that may be used as nucleophiles for this process include carbanion
Carbanion
A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid.where B...
s and enolates.