摘要:

Quinone methides prepared in situ from phenylcoumaran and ß-C-l lignin models which did not contain a ß-hydroxymethyl group, readily formed addition products with anthranol but not with anthrahydroquinone. For ß-aryl lignin models containing the hydroxymethyl group, the retro-aldol reaction (liberating formaldehyde) was so facile under the conditions used that stilbene formation from the quinone methide took precedence over adduct formation.

ISSN:0277-3813    

DOI:10.1080/02773818708085258

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Trimethylsilyl iodide (TMSiI) is a novel reagent to cleave ether bonds selectively under very mild reaction conditions. The authors applied the reagent for the cleavage of the arylglycerol- β -aryl ether bond using a guaiacylglycerol- β -guaiacylether as a model compound. Under the optimum conditions, the above ether bond was cleaved almost quantitatively, and the reaction mechanism turned out not to be direct cleavage proposed by Jung et al., but to be the iodination of the benzyl carbon followed by the formation of a α - β double bond and the cleavage of the β-aryl ether bond.

ISSN:0277-3813    

DOI:10.1080/02773818708085259

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

1H NMR spectral evidence for the occurrence of β-1 structures in lignins it presented. The number of β-1 side chains may be 1–2% in spruce lignin and perhaps as much as 5% in birch lignin.

ISSN:0277-3813    

DOI:10.1080/02773818708085260

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Four dimeric-type compounds (14,15,16, and17) that had been isolated earlier from the catalytic hydrogenolysis products of aspen poplar lignin have been synthesized for structural verification.

ISSN:0277-3813    

DOI:10.1080/02773818708085261

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The xylan fraction of Beech wood was analysed by Curie point pyrolysis gas chromatography mass spectrometry. Chlorinated methoxyphenols were detected among the pyrolysis products. These compounds are released from chlorolignin residues present in the xylan preparation. The chlorination must have occurred during delignification of the holocellulose with sodium chlorite.

ISSN:0277-3813    

DOI:10.1080/02773818708085262

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

High resolution solid state13C CP/MAS NMR has been used to study poplar wood samples before and after steam treatment. The principal structural components of wood have been characterized and the main effects of the rapid steam hydrolysis process (hydrolysis of the hemicelluloses, depolymerization of the lignin) were discussed. Evidence of molecular-level interactions between the principal components have been obtained from T1Hδ relaxation times of protons belonging to the corresponding species.

ISSN:0277-3813    

DOI:10.1080/02773818708085263

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Structural breakdown of the lignin in autohydrolysis-explodedPinus radiataand Eucalyptus regnans wood and in sugarcane bagasse has been examined using cross polarization magic angle spinning (CP/MAS)13C MMR spectroscopy. The alkali- and acetone-insoluble (i.e. residual) lignins have undergone substantial cleavage of the major (β-0-4) interunit linkage and are most likely mixtures of partly depolymerized and repolymerized lignin fragments. Correlations between residual lignin structure, breakdown of the lignocellulose structure and enzymatic digestibility of the cellulosic carbohydrate are proposed.

ISSN:0277-3813    

DOI:10.1080/02773818708085264

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Large additions of O2during the pretreatment of modified or industrial kraft pulp with NO2under conditions which favored an autocatalytic generation of NO2from produced and added HNO3led to a decreased viscosity after a subsequent oxygen bleaching, If the comparison was made at high kappa numbers. The difference was less apparent when the oxygen bleaching was extended. The yield of pulp at a given kappa number was reduced by large O2additions. An Increased yield of nitric acid contributed to these effects.

ISSN:0277-3813    

DOI:10.1080/02773818708085265

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The molecular weights of both the lignosulphonate and carbohydrate fractions leached from sulphite chemimechanical pulps Increased as the leaching proceeded. Lignosulphonate molecular weights rose from 11000 to 61000. Values for the carbohydrate fractions were lower, ranging from 6000 to 17000. For the lignin, the diameter of the equivalent sphere corresponding to the whole sample leached was considerably Higher then the medium-pore diameter of the fiber. This discrepancy Indicated that the lignosulphonate macromolecule in the fiber wall adopted a flat conformation.

ISSN:0277-3813    

DOI:10.1080/02773818708085266

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Different cellulose samples as well as lingo-cellulosic materials which had been pretreated by either organosolv or hydrothermolysis processes were tested as to their degradability by a crude cellulase preparation fromTrichoderma viride. The glucose concentrations in hydrolysate samples were determined by HPLC End-product inhibition of the cellulase complex by glucose and cellobiose was also studied, as were inhibitory effects caused by lignin- and hemicellulose-derived pretreatment side-products.

ISSN:0277-3813    

DOI:10.1080/02773818708085267

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor