Comparative kinetics of the induced radical autocondensation of polyflavonoid tannins. III. Micellar reactions vs. cellulose surface catalysis

✍ Scribed by E. Masson; A. Pizzi; A. Merlin

• Book ID: 102654997
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 708 KB
• Volume: 60
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19960606)60:10<1655::aid-app18>3.0.co;2-3

✦ Synopsis

Cellulose surface catalysis of the induced autocondensation of tannins has been found to occur also for the radical mechanism of the reaction. Equally effective in accelerating pyran ring opening of polyflavonoids by radical mechanisms appears to be the presence of any substance leading to micellar structures in the tannin solution. Thus, soaps and synthetic and natural polymeric colloids have been found to accelerate the reaction. The micellar effect is distinct and different from the surface catalysis of the process induced by cellulose. Amorphous and crystalline cellulose appear to differ somewhat as regards the extent of catalytic activation. As for ionic mechanisms, also for catalyzed radical mechanisms, procyanidins invert their favorite reaction of cleavage of the interflavonoid bond to favor, instead, pyran ring opening. This inversion of the favorite reaction is induced both by the presence of cellulose and by the level of the micellar state of the reaction.