Condensation of lignin

Condensation of Lignins with Formaldehyde. A sample of 10 grams of kraft lignin (45 meq. of OCH3) was dissolved in 50 ml. of IN sodium hydroxide, and commercial (35%) formalin was added, containing 120 mmoles of CH20. The solution was set aside at room temperature for... 

Studies conducted at Masonite Corporation and discussed earlier in this paper reveal that defibra-tion is indeed hydrolytic and produces furfural and mononuclear aromatics. Clearly, the elements of the polycondensation mechanism are available as described by Runkel and Wilke (11). Boehm (15), Klauditz and Stegmann (16), and Gupta et all fl7) go as far as to claim that the high lignin contents of Asplund and Masonite pulps are due to condensation of lignin at high temperatures. 

Gierer J, Petterson I (1977) Study on the condensation of lignins in alkaline media (2) Formation of stilbene and arylcoumaran structures through neighboring group participation reactions Can J Chem 55 593-599... 

Funaoka M, Kako T, Abe I (1990a) Condensation of lignin during heating of wood. Wood Sci Technol 24 277-288... 

Kondo, R. McCarthy, J.L. Condensation of lignins with coniferyl alcohol in alkaline aqueous solutions. J. Wood Chem. Technol. 1985, 5 (1), 37-52. 

J Gierer, I Pettersson. Studies on the Condensation of Lignins in Alkaline Media. Part II. The Formation of Stilbene and Arylcoumaran Structures through Neighbouring Group Participation Reactions. CanJ Chem 55(4) 593-599, 1977. 

J Gierer, O Lindeberg. Studies of the Condensation of Lignins in Alkaline Media. Part III. The Formation of StUbenes, Arylcoumarans and Diarylmethanes on Treatment of Spruce Wood Meal with Alkali and White Liquor in the Presence of Xylenols. Acta Chem Scand B33 5S0-5S2, 1979. 

The inability to solubilize aromatic components of suberin-enriched preparations by the methods used for lignin suggests that suberin structure is distinctly different from that of lignin, probably due to the aliphatic cross-linking and the higher degree of condensation present in suberin. 

The data presented in a recent communication by Freudenberg et al. (32) show that the methoxyl content of the dehydrogenation polymers of coniferyl alcohol do not change with condensation time. However, their reference to p-hydroxycinnamyl alcohols seems to indicate their appreciation of the significance of a p-hydroxyphenylpropane unit in the mechanism of lignin formation. 

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