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Reactions of a-substituted non-phenolic lignin model compounds under alkaline hydrolysis conditionsMirshokraie, S. Ahmad (Seyed Ahmad) January 1988 (has links)
Side-chain ether groups in lignin model compounds of the general structure 1-(3$ sp prime$,4$ sp prime$-dimethoxyphenyl)-1,2-diaryloxyethane exhibited hydrolytic cleavage (the extent depending on the substituents on the 1-aryloxy groups) in aqueous 2N NaOH at 150$ sp circ$C (i.e. under wood pulping conditions). The level of hydrolysis increased in phenylpropane models (i.e. with $ gamma$-CH$ sb2$OH). Thus the commonly accepted generalization that 1,2-diethers of 3$ sp prime$,4$ sp prime$-dimethyoxyphenylpropane are stable in hot alkali is valid only for 1-alkoxy compounds. The newly observed hydrolytic cleavage is influenced by a combination of steric effects, electronic effects and solubility parameters. These observations now make it possible to consider alkaline delignification in the light of gel-degradation theory. / A series of compounds of the general structure 1-(3$ sp prime$-4$ sp prime$,dimethoxyphenyl)-1-aryl-2-guaiacyloxyethane, where the 1-aryl group bore a hydroxy substituent, also exhibited alkaline hydrolysis, at 150$ sp circ$C, at the $ beta$-carbon. The extent was greater when the 1-aryl group bore an $o$-OH than when it bore a $p$-OH. Thus, the reaction was assisted by the nucleophilic attack of the $o$-phenoxide anion on the $ beta$-carbon. / A relatively high release of guaiacol occurred on treatment of 1-(3$ sp prime$,4$ sp prime$-dimethoxyphenyl)-1-thio-2-guaiacyloxyethane with 2N NaOH at 150$ sp circ$C, and the yield of guaiacol was increased when the terminal sidechain carbon bore a $-$CH$ sb2$OH group. Analogous $ alpha$-thioaryl and $ alpha$-thioalkyl compounds also exhibited greater ether cleavage than their oxy counterparts. The hydrolysis of the $ beta$-guaiacyl group was also enhanced by the presence of $ alpha$-seleno-containing groups.
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Improved pulping efficiency in C4H-F5H transformed poplarHuntley, Shannon Kelly 11 1900 (has links)
Changes in wood chemistry could have significant impact on both environmental and economic
aspects of the pulp and paper industry. Consequently, a considerable amount of effort has been
devoted to altering lignin content and/or modifing lignin monomer composition, a cell wall
component whose removal is a major part of the chemical pulping process. Analysis of poplar
transformed with a cinnamate 4-hydroxylase (C4H):ferulate5-hydroxylase (F5H) construct
confirmed significant increases in the mole percent syringyl lignin in transgenic lines. Further,
this study demonstrated significant increases in pulping efficiency from greenhouse grown
transgenic trees. Compared to wild-type pulp, decreases of 23 kappa units (residual lignin) and
increases of >20 ISO brightness units were observed in tree lines exhibiting high syringyl
monomer concentrations (93.5% mol S). These changes were associated with no significant
change in total lignin content or observed phenotypic differences in the trees. Additionally,
pulp yields were not affected by the enhanced removal of lignin.. Furthermore, transgenic lines
exhibit reduced fibre coarseness and increased cellulose viscosity. These results suggest that
C4H-F5H transformed trees could be used to produce pulp for paper with substantially less
severe delignification conditions (lower chemical loading or less energy), and that the pulp
produced is of comparable quality to that of the wild-type poplar. Consequently, the ecological
footprint left on the environment, measured by the amount of deleterious pulping by-products
released into the environment may be significantly reduced.
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The distribution of phenolic hydroxyl groups in the xylem tissue of softwoods /Yang, Juei-Mao January 1977 (has links)
No description available.
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High temperature steam hydrolysis of tulip poplarFieber, Catherine Ann 08 1900 (has links)
No description available.
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Recovery of byproducts in the formation of cellulose pulp by high pressure steam hydrolysis of hardwoodsMann, Timothy Marvin 05 1900 (has links)
No description available.
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The fractionation of lignocellulosicsBonanno, Michael Anthony 08 1900 (has links)
No description available.
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Chlorite delignification of spruce wood.Ahlgren, Per Arne January 1970 (has links)
No description available.
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The topochemistry of delignification reactions.Wood, John Russell. January 1972 (has links)
No description available.
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The distribution of lignin in aspen wood.Musha, Yoshinori. January 1970 (has links)
No description available.
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Physico-chemical mechanisms of delignificationKerr, Allan J. January 1974 (has links)
No description available.
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