Lignin functional groups

Argyropoulos, D. S., Bolker, H. L, Heitner, C., and Archipov, Y. P NMR spectroscopy in wood chemistry. Part V. Qualitative analysis of lignin functional groups. J. Wood Chem. Technol. 13(2),187-212 (1993). 

Quantitative Analysis of Lignin Functional Groups with NMR... 

Experiments were performed by varying both redox system concentration and reaction temperature (Table 1). Homopolymerization of vinyl acetate (Run VAO) was also carried out under the same experimental conditions in the absence of lignin. Moreover, in order to get an insight on the free-radical grafting mechanism, the polymerisation of vinyl acetate was performed under the same conditions in the presence of 2-methoxy-4-methylphenol (MAF), a model compound of lignin functional groups. 

Formation and Elimination of Multiple Bond Functionalities. Reactions that involve the formation and elimination of multiple bond functional groups may significantly effect the color of residual lignin in bleached and unbleached pulps. The ethylenic and carbonyl groups conjugated with phenoHc or quinoid stmctures are possible components of chromophore or leucochromophore systems that contribute to the color of lignin. 

Proton and carbon-13 nmr spectroscopy provides detailed information on all types of hydrogen and carbon atoms, thus enabling identification of functional groups and types of linkages ia the lignin stmcture. Detailed a ssignments of signals ia proton and carbon-13 nmr spectra have been pubHshed... 

Functional Group Analysis. The total hydroxyl content of lignin is determined by acetylation with an acetic anhydride—pyridine reagent followed by saponification of the acetate, and followed by titration of the resulting acetic acid with a standard 0.05 W sodium hydroxide solution. Either the Kuhn-Roth (35) or the modified Bethge-Liadstrom (36) procedure may be used to determine the total hydroxyl content. The aUphatic hydroxyl content is determined by the difference between the total and phenoHc hydroxyl contents. 

Common chemistries include tannins and lignins but also more modem polyacrylates and derivatives, which often act as carriers for specific functional groups and provide novel chemistry molecules. The polyacrylates may also be copolymerized, perhaps with maleates [maleic anhydride, cis-butenedioic anhydride (OCOCHrCHCO) is the usual starting point material], styrene (vinylbenzene, phenylethylene,... 

One solution to this problem is to create new copolymers of lignin which have the appropriate functional groups to perform effectively in a given environment. One such class of new materials with the right parts to function where anionics fail is the class of cationic polymers. Data from such a copolymer will now be presented. 

Functional food enhancers, 11 14 Functional food market, 17 674 Functional foods, 17 646 Functional fragrances, 18 361-364 Functional group analysis, for lignin, 15 10-12... 

Since lignin is not a uniform entity, chemical criteria for its characterization have centred around analytical detenninations of its functional groups, e.g. total hydroxyl content, phenolic hydroxyls (56), methoxyl and other ether groups, benzyl alcohol groups (7a), carbonyl groups (6), etc., and estimations of its content of special structural features, e.g. phenylcoumaran units (5), biphenylyl linkages (123), etc. 

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