Lignin phenolics oxidation

Organophilic polyphenolic materials for oil-based drilling fluids have been described [407], The additives are prepared from a polyphenolic material and one or more phosphatides. The phosphatides are phosphoglycerides obtained from vegetable oils, preferably commercial lecithin. Humic acids, ligno-sulfonic acid, lignins, phenolic condensates, tannins the oxidized, sulfonated, or sulfomethylated derivatives of these polyphenolic materials may serve as polyphenolic materials. 

MnP catalyzes hydrogen-peroxide-dependent oxidation of Mn to Mn, which in turn oxidizes phenolic components of lignin [102]. Oxidative demethylation, dechlorination, and decolorization of bleach plant effluent by the MnP of Phanerochaete chrysosporium has been demonstrated [103,104]. 

We found that when phenols (or lignins) are oxidized in alkaline media the initial step is a one-electron abstraction from the phenolic hydroxyl group forming a phenoxyl radical. We discovered an electrochemical method which allows us to determine roughly the free enthalpy of this particular reaction (phenol —> phenoxyl radical). This method has been... 

The phenolic hydroxyl and etherified benzyl alcohol group can be selectively oxidized by periodate [385] and 2,3-dichloro-5,6-dicyano-l, 4-benzoquinone (DDQ) [386], respectively. The periodate oxidation of guaiacyl and syringyl nuclei yields 0-quinones plus methanol and has been used to estimate the phenolic hydroxyl group content of lignin. DDQ oxidation has been applied to estimate the content of lignin-carbohydrate linkages [28]. 

Many past studies on the enzymes of lignin decomposition focused on phenol-oxidizing enzymes, such as laccase and peroxidase, produced by white-rot fungi. It is unlikely, however, that this type of activity is important in structural decomposition (33), although the enzymes may have some other role in lignin decomposition (28). 

Lignin Analysis. Lignin present in fulvic and humic acids from stream, foam, and foam-extract samples from Como Creek and the Suwannee River were oxidized to phenolic oxidation products by copper oxide oxidation via the method described by Hedges and Ertel (24). These phenolic oxidation products then were derivatized to trimethyl silyl derivatives for GC/MS analysis. 

The bulk chemical composition of seawater DOM (Table 8.8), however, is not consistent with a predominant riverine origin. In particular, seawater DOM is depleted in C and enriched in C and compared with most DOM discharged by rivers (with the Amazon being taken here as an example). Seawater DOM is also depleted in aromatic carbon (as measured by C NMR) and lignin phenol structural units (as determined by CuO oxidation), possibly as a consequence both of the low phenol content of marine plankton, and of selective alteration of aromatic carbon by photodegradation. Thus all evidence to date, including elevated total concentrations in surface marine waters (Fig. 8.19), indicates that seawater DOM is largely... 

Harkin, J. M. (1967) Lignin A natural polymeric product of phenol oxidation. In Taylor, W. L, and Battersby, A. R. (eds). Oxidative Coupling of Phenols, Marcel Dekker, New York. 

The reactions between lignin phenolic structures and oxygen have been the subject of numerous studies. In this work, the oxidation mechanisms, the detailed... 

G Strumila and H Rapson. Reaction products of neutral peracetic acid oxidation of model lignin phenols. Pulp Paper Can. 76 T276-T280, 1975. 

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