Southern Research Station

Title: Formaldehyde condensation products of model phenols for conifer bark tannins

Author: Hemingway, R.W.; McGraw, G.W.

Date: 1978

Source: Journal of Liquid Chromatography 1(2):163-179

Description: Gel permeation chromatograpy of the condensation products of phenols and formaldehyde proved effective in understanding the reactions of condensed tannins with formaldehyde. Rates of condensation of phloroglucinols, resorcinols, catechols, (+)catechin, and (-)epicatechin were examined to determine if methylol-tannins from southern pine bark could be prepared as resin intermediates. The phloroglucinols (models for the A-ring of pine bark tannins) were so much more reactive than were the resorcinols (models for the A-ring of wattle tannins), that preparation of methylol-tannins from pine bark tannins seems unlikely even though this approach has been applied successfully to synthesis of resins from wattle tannins. The methylol content of catechin-formaldehyde condensation products was very low. The catechol B-ring was unreactive under conditions in which condensations of pine bark tannins could be controlled. Although there is much less steric hindrance of the A-ring of (-)epicatechin than of (+)catechin, differences in the rates of condensati on of these isomers were not detected. GPC and H-NMR spectra of (+)catechin condensation products showed that a dimer formed rapidly and that further condensation occurred more slowly.

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Citation

Hemingway, R.W.; McGraw, G.W.  1978.  Formaldehyde condensation products of model phenols for conifer bark tannins.   Journal of Liquid Chromatography 1(2):163-179