Abstract
Reaction of a condensed flavonoid tannin, namely mimosa tannin extract with a hexamethylene diamine, has been investigated. For that purpose, catechin was also used as a flavonoid model compound and treated in similar conditions. Solid-state cross-polarisation/magic-angle spinning (CP-MAS) carbon 13 nuclear magnetic resonance (13C NMR) and matrix assisted laser desorption ionisation time of flight (MALDI-ToF) mass spectroscopy studies revealed that polycondensation compounds leading to resins were obtained by the reaction of the amines with the phenolic hydroxy groups of the tannin. Simultaneously, a second reaction leading to the formation of ionic bonds between the two groups occurred. These new reactions have been shown to clearly lead to the reaction of several phenolic hydroxyl groups, and flavonoid unit oligomerisation, to form hardened resins.
Highlights
Condensed polyflavonoid tannin extracts are mostly composed of flavan-3-ols repeating units and smaller fractions of polysaccharides and simple sugars [1]
Mimosa tannin (2 g) was mixed with 2 g of HMDA (70% solution in water) and 0.6 g of a 65 wt % aqueous solution p-toluenesulfonic acid
While some of the peaks obtained by MALDI-ToF in the products obtained by reactions at 185 ◦ C
Summary
Condensed polyflavonoid tannin extracts are mostly composed of flavan-3-ols repeating units and smaller fractions of polysaccharides and simple sugars [1]. The amination of the pyrogallol Bwith relative ease [14], mainly to prepare carbonized materials richer in nitrogen These amination ring by NH3/water is a regioselective amino-substitution of phenolic hydroxyl groups and proceeds reactions, notconditions appear towithout lead toa long oligomers to crosslinked resins. The aim richer of this was to obtain proceeds withinvestigated relative ease [14], mainly to prepare carbonized in work nitrogen These amination did initial not appear to lead to long andamines to crosslinked thermoset resinsreactions, having ahowever, very rapid gelling either (i) byoligomers using only and polyamines as resins.
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