Lignin alkaline hydrogenation

The Structure of Dimers from the Alkaline Hydrogenation of Lignin... 

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. 

In summary, we have isolated and identified two dimeric compounds from the alkaline hydrogenation of sugar maplewood lignin—namely, 1,2-(4,4 -dihydroxy-3,3, 5,5 -tetramethoxydiphenyl)-ethane (I) l,2-(4,4 -... 

It appears justifiable to propose mechanisms for the formation of the monomeric and dimeric products of the alkaline hydrogenation of lignin. 

The isolation of 2,2 -dihydroxy-3,3 -dimethoxy-5,5 -dialkylbiphenyls from both neutral (IS) and alkaline hydrogenation supports Pew s proposal that the biphenyl structure is of considerable importance in lignin... 

Coniferaldehyde structures are the major leucochromophore present in spruce lignin. These end groups are also present to a large extent in unbleached mechanical pulps and are responsible for a major portion of the absorption of UV-radiation above 350 nm. Mild sulfite treatment leads to a considerable reduction in the content of coniferaldehyde structures. After bleaching of mechanical and chemimechanical pulps with alkaline hydrogen peroxide, coniferaldehyde structures are to a large extent eliminated and they cannot be considered to be major contributor to the photo-... 

Lee, D.Y. and Sumimoto, M., "Mechanochemistry of Lignin. V. An Intensive Chromophore in Mechanical Pulps Bleached With Alkaline Hydrogen Peroxide", Hokforschmg, 1991, 45 (Supplement), 15. 

Bhattacharya A, Schuerch C (1960) Lignin from the alkaline hydrogenation of sugar maple-wood III Chromatographic separation of higher molecular weight fractions and a structural study TAPPI 43 840-844... 

Corbett JF (1966) The chemistry of hydroxyquinones. Part I. The reaction of 2-hydroxybenzoquinones with alkaline hydrogen peroxide. J Chem Soc (C) 2308-2311 Corbett JF, Fooks AG (1967) The chemistry of hydroxy-quinones. Part III. The reactions of 2,5-dihydroxy-benzoquinones with alkali. J Chem Soc (C) 1909-1913 Dence CW (1971) Halogenation and nitration. In Sarkanen KV, Ludwig CH (eds) Lignins. 

M.B. Hocking and J.P. Crow, On the Mechanism of Alkaline Hydrogen Peroxide Oxidation of the Lignin Model p-Hydroxyacetophenone. Can. J. Chem. 72, 1137-1142 (1994). 

G Gellerstedt, HL HardeU, and EL Lindfors. The Reactions of Lignin with Alkaline Hydrogen Peroxide. Part fV. Products from the Oxidation of Quinone Model Compounds. Acta Chem. Scand. B 34 669-673, 1980. 

Mechanical pnlps are bleached with as little dissolved organic matter as possible either reductively with dithionite (Y) (hydrosulfite) or oxidatively with alkaline hydrogen peroxide (P). This so-called lignin retaining bleaching cannot produce a completely white fiber since trace amounts of chromophoric structures seem to be either inaccessible or nnreactive to the bleaching agent. 

R Agnemo, G Gellerstedt. The reactions of lignin with alkaline hydrogen peroxide. Part 11. Eactors influencing the decomposition of phenolic structures. Acta Chem Scand B33 337-342, 1979. 

S Omori, CW Dence. The reactions of alkaline hydrogen peroxide with lignin model dimers. Part 2. Gnaiacylglycerol-P-gnaiacyl ether. Wood Sci Technol 15 113-123, 1981. 

G Gellerstedt, R Agnemo. The reactions of lignin with alkaline hydrogen peroxide. Part... 

Alkaline Hydrogen Peroxide as a Lignin-Retaining Bleaching Agent..443... 

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