Removal of Phenolic Hydroxyl Groups in Lignin Model Compounds and Its Effect on Photostability

Holzforschung ◽  
2000 ◽  
Vol 54 (2) ◽  
pp. 127-132 ◽  
Author(s):  
Thomas Q. Hu ◽  
Graham R. Cairns ◽  
Brian R. James
Keyword(s):  
Hydrogen Transfer ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Whatman Filter Paper ◽  
Elemental Analyses ◽  
Catalytic Hydrogen ◽  
Lignin Model ◽  
Phenolic Hydroxyl Groups

Summary The phenolic hydroxyl groups in the lignin model compounds, 2-methoxy-4-propylphenol and 4-hydroxy-3-methoxyacetophenone, were removed by first converting the hydroxyl groups to the trifluoromethanesulfonates (triflates) and then cleaving the triflate substituents via catalytic hydrogen transfer. The products, 1-methoxy-3-propylbenzene and 3-methoxyacetophenone, were characterized by 1H and 13C NMR, mass spectrometry and elemental analyses. The effect of the removal of the phenolic groups on the photostability of the model compounds was evaluated by impregnating the compounds into Whatman filter paper sheets, and subjecting them to an accelerated yellowing experiment in a UV chamber. The removal of the phenolic groups resulted in a significant yellowing inhibition, with a higher photostabilizing effect than methylation or acetylation of the hydroxyl, particularly for the model compound without an α-carbonyl group.

Self-hydrogen transfer hydrogenolysis of β-O-4 linkages in lignin catalyzed by MIL-100(Fe) supported Pd–Ni BMNPs

2017 ◽  
Vol 19 (19) ◽  
pp. 4538-4543 ◽  
Author(s):  
Jia-wei Zhang ◽  
Guo-ping Lu ◽  
Chun Cai
Keyword(s):  
Hydrogen Transfer ◽  
Catalytic Performance ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Organosolv Lignin ◽  
Lignin Model ◽  
Intramolecular Transfer ◽  
Supported Pd

A MIL-100(Fe) supported Pd–Ni BMNP catalyst has been fabricated, and the catalyst exhibits superior catalytic performance toward intramolecular transfer hydrogenolysis of lignin model compounds and organosolv lignin.

scholarly journals Study of the Reactivity of Lignin Model Compounds to Fluorobenzylation Using 13C and 19F NMR: Application to Lignin Phenolic Hydroxyl Group Quantification by 19F NMR

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3211
Author(s):  
Esakkiammal Sudha Esakkimuthu ◽  
Nathalie Marlin ◽  
Marie-Christine Brochier-Salon ◽  
Gérard Mortha
Keyword(s):  
Reaction Medium ◽  
19F Nmr ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Nmr Analysis ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Wide Range ◽  
Lignin Model ◽  
13C And 19F Nmr

Lignin is an aromatic biopolymer derived from lignocellulosic biomass. Providing a comprehensive structural analysis of lignin is the primary motivation for the quantification of various functional groups, with a view to valorizing lignin in a wide range of applications. This study investigated the lignin fluorobenzylation reaction and performed a subsequent 19F-NMR analysis to quantify hydroxyl groups, based on a work developed two decades ago by Barrelle et al. The objectives were to check the assignments proposed in this previous study and to examine the reactivity of various types of lignin hydroxyls with the derivatization agent. Selected lignin model compounds containing phenolic and aliphatic hydroxyls were subjected to the fluorobenzylation reaction, and the obtained reaction medium was analyzed by 13C and 19F NMR spectroscopy. The model compound results showed that phenolic hydroxyls were totally derivatized, whereas aliphatic hydroxyls underwent minimal conversion. They also confirmed that 19F NMR chemical shifts from −115 ppm to −117.3 ppm corresponded to phenolic groups. Then, a 19F NMR analysis was successfully applied to Organosolv commercial lignin after fluorobenzylation in order to quantify its phenolic group content; the values were found to be in the range of the reported values using other analytical techniques after lignin acetylation.

Article

1998 ◽  
Vol 76 (5) ◽  
pp. 612-622
Author(s):  
Zhi-Hua Jiang ◽  
Dimitris S Argyropoulos
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Magnetic Resonance ◽  
Mannich Reaction ◽  
Phenolic Hydroxyl ◽  
Ambient Conditions ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
The Mannich Reaction

The reactivity of lignin model compounds under Mannich conditions with piperidine and formaldehyde was studied. The piperidinomethyl group was confirmed to be introduced quantitatively at sterically unhindered positions ortho to a phenolic hydroxyl when the substrate was allowed to react under ambient conditions. The sequential application of the Mannich reaction followed by quantitative 31P NMR on a variety of lignin samples allowed the amounts of various aromatic groups bearing free phenolic hydroxyls to be determined. More specifically, the technique allowed the quantification of para-hydroxyl phenols, catechols, guaiacols, and phenols bearing C5 or C6 substituents. The quantitative reliability of the technique was also examined with a series of dissolved kraft lignins, isolated at various degrees of delignification. The data were found to favourably compare to those obtained by permanganate oxidation.Key words: lignin, lignin model compounds, Mannich reaction, nuclear magnetic resonance (NMR), phenols, phosphorus, piperidine, quantitative analysis.

Solid-state 29Si NMR and FTIR analyses of lignin-silica coprecipitates

Holzforschung ◽  
2016 ◽  
Vol 70 (8) ◽  
pp. 709-718 ◽  
Author(s):  
Yohanna Cabrera ◽  
Andrés Cabrera ◽  
Flemming H. Larsen ◽  
Claus Felby
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Underlying Mechanism ◽  
Silica Particles ◽  
Agricultural Residues ◽  
Hydroxyl Groups ◽  
29Si Nmr ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model

Abstract When agricultural residues are processed to ethanol, lignin and silica are some of the main byproducts. Separation of these two products is difficult and the chemical interactions between lignin and silica are not well described. In the present study, the effect of lignin-silica complexing has been investigated by characterizing lignin and silica coprecipitates by FTIR and solid state NMR. Silica particles were coprecipitated with three different lignins, three lignin model compounds, and two silanes representing silica-in-lignin model compounds. Comparison of 29Si SP/MAS NMR spectra revealed differences in the distribution of silanol hydroxyl groups among different coprecipitates. These differences are dependent on the lignin type. The results are interpreted that the underlying mechanism of the interactions is the formation of hydrogen bonds between lignin aliphatic hydroxyl or carboxyl groups and the silanols, but not a condensation of the silica-in-lignin among the silica particles and not the formation of C-O-Si bonds.

Infrared spectra of lignin model compounds and of lignins from Eucalyptus regnans

1966 ◽  
Vol 19 (12) ◽  
pp. 2285 ◽  
Author(s):  
AJ Michell
Keyword(s):  
Solid State ◽  
Infrared Spectra ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Model Compounds ◽  
Eucalyptus Regnans ◽  
Lignin Model Compounds ◽  
Solvent Dependence ◽  
Lignin Model ◽  
Stretching Vibrations

Infrared spectra in the O-H and C=O stretching regions of lignin model compounds and of lignins isolated in various ways from Eucalyptus regnans F. Muell. have been obtained for samples both in the solid state and in solution. The effects of solvents on the stretching vibrations of free and intramolecularly bonded hydroxyl groups have been examined for a number of the model compounds, including some in which the groups are subject to steric hindrance. The results have been used to interpret the O-H stretching frequencies of the lignins in the same solvents. In the lignin macromolecules all hydroxyl groups appear to be involved in hydrogen bonds, and the phenolic groups are sterically hindered.��� Different solvent effects have also been observed in model compounds between the C=O stretching frequencies of carboxyl groups and those of aldehyde, ketone, and ester groups. The solvent dependence of the 1665 cm-1 band in the lignin spectra supports its assignment to a conjugated aldehyde or ketone group, but the dependence of the 1725 cm-1 band suggests that both carboxyl and carbony1 groups may contribute to the band envelope.

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