Reaction G Aldehyde-Amine Condensation

Aldehydes, particularly a,/Tunsaturatcd ones, react readily at low temperatures with amines to give polymeric high molecular mass, coloured products of unknown structure, called melanoidins. Heterocyclic ring systems, such as pyridines, pyrazines, pyrroles, and imidazoles, have been shown to be present. Melanoidins usually contain 3 4% nitrogen. 

The constitution of the melanoidins differs somewhat, depending on how they have been produced, for example  

2-oxopropanal + glycine high enolic hydroxyl and low ether content 

As the condensations proceed, higher molecular mass products are formed, long-period products being non-dialysable. 

Some work by Benzing-Purdie et al.69 bears on this, as can be seen from Table 2.3. The following comments are worth making  

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Reaction G Aldehyde-amine condensation and formation of heterocyclic nitrogen compounds... 

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