Carbonyl lignin structures containing

Because of the complexity of lignin structure, a number of the following lignin model compounds (containing phenolic and carbonyl functions) have been photolysed [33, 981, 2180] ... 

It should be noted that if the non-phenolic Ca-carbonyl compound contains an aromatic ring without Ca-carbonyl group (i.e., the structure should contain at least two aromatic rings), then the compound will be a substrate for lignin peroxidase and will be degraded according to the mechanisms discussed above. Degradation of this type of compounds can result, for example, in the formation of vanillin and vanillic acid derivatives (see compounds 7a and 8). As has been shown by Eriksson and coworkers... 

A typical Py-GC-MS trace from a wood sample (Figure 9) contains 50-100 individual peaks corresponding to at least that many products. The individual pyrolysis products include fiirans plus a variety of carbonyl compounds that are typical of polysaccharides, particularly cellulose and hemi-cellulose (42). In addition, many different lignin-derived phenols are obtained that, like the CuO reaction products, retain the methoxylation pattern of the parent structural units and carry diagenetic information on their side chains (43). Characteristic pyrolysis products of wood extractives such as resin acids also can be detected (44) thus, this analytical method is... 

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