1,721,253 research outputs found
Prodotti ad elevato valore aggiunto e nuovi materiali mediante ossifunzionalizzazione selettiva di biomasse
No full textChemistry and materials. Italic 4. Wood, 100 years of structural studies
No full textNonostante la prima caratterizzazione strutturale della lignina risalga al 1908 molto è ancora ignoto circa la struttura dei materiali lignocellulosici. Italic 4 ha dedicato una sessione agli avanzamenti nel settore, focalizzata principalmente sull’identificazione e caratterizzazione di interazioni supramolecolari in biopolimeri vegetali
Reactivity of phenolic and nonphenolic residual kraft lignin model compounds with Mn(II)-peroxidase from Lentinula edodes
No full textOn the role of 1-hydroxybenzotriazole as mediator in laccase oxidation of residual kraft lignin
No full textSINGLET OXYGEN IN THE PHOTODEGRADATION OF LIGNIN MODELS
No full textThe photochemical oxidation of lignin models in the presence of singlet
oxygen nas studied. The treatment of the non-phenolic beta-O-4 aryl
ether derivatives 6, 7, and 8 in the presence of both oxygen and Rose
Bengal gave products deming from a formal beta-C-O cleavage formation.
By this way the derivatives 12. 13, and 15 were obtained, The
photochemical oxidation of the phenolic beta-O-4 aryl ehter 9 gave the
same type of product confirming that, in this case, the presence of the
carbonyl group is not indispensable to have the cleavage reaction. The
use of the model compound 10 showed that. When the phenoxy part of the
molecule shows a lower reactivity towards singlet oxygen, the oxidation
of the phenol moiety to hydroquinone call occur. The photochemical
behaviour of these model compounds can be rationalised from a reaction
of singlet oxygen with the phenoxy part of the molecule. (C) 1997
Published by Elsevier Science Ltd
Tannins characterization by 31P-NMR
No full textTannins are secondary metabolites of plants employed as insect and parasite repellent to prevent plague tissues. This peculiarity is related to the inhibition of extracellular enzymes that occurs through the complexation of peptides by means of several cross linking hydrogen bond with their many phenolic functions. The characteristics of these interactions are not completely clear, as the structure of these heterogeneous polyphenols molecules. We developed a new analytical method for the structural characterization of tannins based on the 31P-NMR technique that allows both the quantitative and the qualitative characterisation of all labile OH groups present in tannins
Photodegradation of lignin: The role of singlet oxygen
No full textThe photochemical irradiation of some phenoxyacetophenone derivatives in
the presence of oxygen by using visible light did not produce any
decomposition product. In the presence of singlet oxygen, sensitized by
using Bengal Rose, decomposition products were obtained. The products
obtained were similar to those obtained by direct beta-C-O cleavage on
the substrate. In this case, the observed behavior can be explained
assuming an attack of singlet oxygen on a phenoxy part of the molecule
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