Mannich base
Encyclopedia
A mannich base is a beta-amino
-ketone
, which is formed in the reaction of an amine
, formaldehyde
(or an aldehyde
) and a carbon acid . The Mannich base is an endproduct in the Mannich reaction
, which is nucleophilic addition reaction
of a non-enolizable
aldehyde and any primary or secondary amine
to produce resonance stabilized imine
(iminium ion or imine salt). The addition of a carbanion from a CH acidic compound (any enolizable carbonyl compound, amide, carbamate, hydantoin or urea) to the imine gives the Mannich base.
to form enals and enone
s.
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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
-ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
, which is formed in the reaction of an 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 Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.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,...
, formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
(or an aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
) and a carbon acid . The Mannich base is an endproduct in 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...
, which is nucleophilic addition reaction
Addition reaction
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....
of a non-enolizable
Enol
Enols are alkenes with a hydroxyl group affixed to one of the carbon atoms composing the double bond. Alkenes with a hydroxyl group on both sides of the double bond are called enediols. Deprotonated anions of enols are called enolates...
aldehyde and any primary or secondary 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 produce resonance stabilized 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...
(iminium ion or imine salt). The addition of a carbanion from a CH acidic compound (any enolizable carbonyl compound, amide, carbamate, hydantoin or urea) to the imine gives the Mannich base.
Reactivity
With primary or secondary amines, Mannich bases react with additional aldehyde and carbon acid to larger adducts HN(CH2CH2COR)2 and HN(CH2CH2COR)2. With multiple acidic hydrogen atoms on the carbon acid higher adducts are also possible. Ammonia can be split off in an elimination reactionElimination 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...
to form enals and enone
Enone
An enone is an unsaturated chemical compound or functional group consisting of a conjugated system of an alkene and a ketone. The simplest enone is methyl vinyl ketone or CH2=CHCOCH3....
s.