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 ^[1]. 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.^[2]

Base catalysed Mannich reactionv forming 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 reaction to form enals and enones.

References

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