Lignin, degradation products

Tsutsuki, K., Kondo, R. and Shiraishi, H. (1993). Composition of lignin-degradation products, lipids and opal phytoliths in a peat profile accumulated since 32,000 years B.P. in Central Japan. Soil Science and Plant Nutrition 39 463-474. 

However, in the light of the results presented herein, this cannot be stated unequivocally, otherwise it would follow that only guaiacyl type compounds would be obtained as softwood lignin degradation products. It has been found that the native lignin from the softwood white Scots pine also yields p-hydroxybenzaldehyde upon oxidation. Thus, it seems that either coniferyl alcohol is not the only lignin progenitor in woody tissues, or that this coniferyl compound is preceded in the process of... 

Lnndquist, K. The Separation of Lignin Degradation Products. Acta Chem. Scand. IS. 1316-1317 (1964). 

Aromatic compounds are present but do not constitute a predominant part of the molecule the polyphenollc and polyaromatic components are low in concentration and exhibit low degrees of substitution Aliphatic side chains are attached to the aromatic core, but due to the participation of lignin degradation products, aromatic moieties are more abundant... 

High-Performance Polymers from Lignin Degradation Products... 

In conclusion, DOM in water is a complex mixture of degraded moderate-sized biomolecules. As degradation proceeds in the aquatic environment, carbohydrates and lignin degradation products disappear within days to a few years. Only the carboxylated aliphatic alicyclic component persists for thousands of years in the marine environment (35) or in isolated lake environments like Big Soda Lake, Nevada. 

To our knowledge, the coumarone ketol (XXII) is the first crystalline dimeric lignin degradation product with two complete phenylpropane skeletons which has been reported in the literature 26). On the basis of the model experiments discussed above, the presence of the ketol side chain as well as the phenylcoumarone system in (XXII) indicates that the origin of the product is a sequence of three phenylpropane monomers (XXVIII) in lignin, involving a phenylcoumaran system carrying a gly-... 

Earlier research involving reaction conditions that led to only cyclohexyl derivatives has been followed by the ability to isolate and characterize relatively high yields of phenolic lignin degradation products under much milder conditions. This gives direct supporting evidence for the essentially aromatic nature of lignin. 

Under alkaline conditions isolating lignin degradation products which are essentially of a phenyl.ethyl rather than a phenylpropyl nature is structurally important and requires a lignin structure by which the 7-carbon may be removed as a result of a 0-7 carbon-carbon cleavage reaction, either by direct alkaline hydrolysis or alkali-catalyzed hydrogenolysis. 

Table III shows the results of such a study. The variation in the nature of the lignin degradation products with initial pH follows the same general pattern as observed using aspen wood—i.e., an increased percentage of the phenylpropane over the phenylpropanol derivative in acid medium and the almost sole production of phenylethane products under alkaline conditions. The total yield of identified products, based on original Klason lignin, is significantly less than that for aspen (Table I).

We now wish to report our results on isolating lignin-derived dimers by alkaline hydrogenation and to propose mechanisms for their formation. In addition, we will present some information on the (NMR) spectra of these and related compounds this technique has been useful for analyzing the structure of lignin degradation products and related synthetic materials. 

The spent bleach liquors are complicated mixtures of reaction products, only some of which have been identified. A simple classification according to the type of compounds present has been made in Table 8-4. As can be seen, lignin degradation products dominate in the spent liquors from chlorination and alkali extraction. Because of extensive demethylation of lignin, considerable amounts of methanol are present in the chlorination liquors. The amount of low molecular chlorinated aromatics is very low, but since the most toxic compounds are included in this fraction, clarification of its complicated composition has been the subject of intensive research. 

Kleen, M. and Gellerstedt, G., Influence of inorganic species on the formation of polysaccharide and lignin degradation products in the analytical pyrolysis of pulps. J Analytical Appl Pyrolysis 1995, 35 (1), 15-41. 

Fig. 4.7.6. Influence of film thickness (A = 0.25 pm, B - 1.0 pm) on the retention of beech wood pyrolysis products. Column medium, chemically bonded OV-1701. Peaks labeled with letters are carbohydrate-derived products numbered peaks correspond to lignin degradation products (see Table 4.7.1)...

A lignin sample free of contaminants not chemically bonded to lignin such as carbohydrates, extractives, and monomeric, dimeric, and oligomeric lignin degradation products... 

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