Studies on the dehydrogenative polymerization of monolignol β-glycosides: Part 5. UV spectroscopic monitoring of horseradish peroxidase-catalyzed polymerization of monolignol glycosides

Holzforschung ◽  
2008 ◽  
Vol 62 (5) ◽  
Author(s):  
Yuki Tobimatsu ◽  
Toshiyuki Takano ◽  
Hiroshi Kamitakahara ◽  
Fumiaki Nakatsubo
Keyword(s):  
Horseradish Peroxidase ◽  
Uv Spectroscopy ◽  
Oxidative Polymerization ◽  
Quinone Methide ◽  
Hydroxyl Groups ◽  
Aryl Ether ◽  
Spectroscopic Monitoring ◽  
Phenolic Hydroxyl Groups ◽  
Dehydrogenation Polymer

Abstract Horseradish peroxidase (HRP)-initiated dehydrogenative polymerizations of guaiacyl (G) and syringyl (S)-type monolignol γ-O-glucosides, isoconiferin (iso-G) and isosyringin (iso-S), which contain a hydrophilic glucosyl unit on γ-position of coniferyl alcohol (G-alc) and sinapyl alcohol (S-alc), respectively, were monitored by UV spectroscopy to study the formation of dehydrogenation polymer (DHP, lignin polymer model) in a homogeneous aqueous phase. During homopolymerization of iso-S, a new absorbance band at 325 nm (A 325) rapidly increased in intensity and then gradually disappeared, whereas such stable changes in absorbance were not observed during homopolymerization of iso-G. During polymerization of iso-S, A 325 rapidly disappeared when an acid, nucleophile or reductant was added to the reaction mixture, indicating that A 325 can be attributed to S-type quinone methide intermediates (QMs). Similar to iso-S polymerization, temporary absorbance at 328 nm was observed during conventional polymerization of S-alc. We interpret this observation as follows: S-type QMs accumulated in the reaction mixture and the progress of subsequent DHP formation during oxidative polymerization of iso-S or S-alc was hindered. UV monitoring of iso-G and iso-S copolymerization revealed that the presence of iso-G promoted the disappearance of A 325. Furthermore, S-type QMs generated in situ by iso-S polymerization disappeared more rapidly after guaiacol addition than after 2,6-dimethoxyphenol addition. The following mechanism for copolymerization of iso-G and iso-S can be proposed: G-type precursors with phenolic hydroxyl groups react readily by nucleophilic addition with the α-C of S-type QMs, and the molecular chains of DHPs increase via non-cyclic α-aryl ether bonds.

Studies on the dehydrogenative polymerization of monolignol β-glycosides. Part 6: Monitoring of horseradish peroxidase-catalyzed polymerization of monolignol glycosides by GPC-PDA

Holzforschung ◽  
2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Yuki Tobimatsu ◽  
Toshiyuki Takano ◽  
Hiroshi Kamitakahara ◽  
Fumiaki Nakatsubo
Keyword(s):  
Horseradish Peroxidase ◽  
Reaction System ◽  
Water Soluble ◽  
Quinone Methide ◽  
Efficient Production ◽  
Hydroxyl Groups ◽  
Photodiode Array Detection ◽  
Dehydrogenative Polymerization

Abstract Horseradish peroxidase (HRP)-catalyzed dehydrogenative polymerization of guaiacyl (G) and syringyl (S)-type monolignol γ-O-glucosides, isoconiferin (iso-G) and isosyringin (iso-S), which contain a hydrophilic glucosyl unit on γ-position of coniferyl alcohol and sinapyl alcohol, respectively, was monitored by gel permeation chromatography coupled with photodiode array detection (GPC-PDA). Contrary to the conventional dehydrogenative polymerization of monolignols, the polymerization of the glycosides produces water-soluble synthetic lignins (DHPs) in a homogeneous aqueous phase. Taking advantage of this unique reaction system, the method was developed to follow the changes of molecular weights in the course of DHP formations. Moreover, PDA detection permits determination of oligomeric S-type quinone methide intermediates (QMs) formed as stable transient compounds during polymerization of iso-S. A detailed comparison of the polymerization profiles revealed entirely different behaviors of G- and S-type monomers. The data strongly support the view that the low reactivity of oligomeric S-type QMs impedes the formation of DHPs from S-type monomers. In copolymerization of G- and S-type monomers, it is conceivable that G-type phenolic hydroxyl groups serve as good nucleophilic reactants to scavenge S-type QMs resulting in efficient production of DHPs. As a consequence, the present approach can be a powerful tool to study the in vitro dehydrogenative polymerization providing further mechanistic insights into lignin polymerization in vivo.

Preparation of a Larch Bark-Based Composite and its Properties

2011 ◽  
Vol 183-185 ◽  
pp. 2005-2009
Author(s):  
Lu Wang ◽  
Shu Jun Li ◽  
Pei Pei Liu ◽  
Guang Shou Feng ◽  
Hao Zhong
Keyword(s):  
Moisture Absorption ◽  
Renewable Resource ◽  
Molar Ratio ◽  
Total Phenolic ◽  
Hydroxyl Groups ◽  
Fossil Energy ◽  
Whole Process ◽  
Swelling Rate ◽  
Phenolic Hydroxyl Groups

With the depletion of fossil energy, biology material is getting more and more attention. Bark, as a kind of renewable resource, need to be utilized urgently and reasonably. The larch bark was very extensive in northeast and the use of larch bark is limited to make tannin. However, the whole process produced much bark residue, which could not be utilized effectively. In this paper, based on the content of total phenolic hydroxyl groups, the in-situ synthesis reaction of the larch bark with formaldehyde was performed in different ratios. FTIR analysis was adopted to characterize the synthesized products. After air-drying, the synthesized product was pressed into a bark-based composite under pressure of 10~25 MPa. The effect of pressure and molar ratio of phenols and formaldehyde on the properties of the composite were analyzed. These results indicate that, pressure and molar ratio were both vital factors. The composite with higher molar ratio of phenol and formaldehyde had better abilities of anti-moisture, but the molar ratio of 1:2 made the strongest composite. With the increasing of pressure, the hardness of the composite was greater. For the composite made under 20 MPa and the molar ratio of 1:2, its hardness was 23.41 MPa and its max load was 415.83N. Its thickness and diameter swelling rate of moisture absorption in 12 d was 1.87% and 0.68%.

Laccase-Catalyzed Dyeing and Finishing of Textiles with Gallic Acid

2013 ◽  
Vol 631-632 ◽  
pp. 608-612
Author(s):  
Sha Sha Sun ◽  
Ren Cheng Tang
Keyword(s):  
Gallic Acid ◽  
Oxidation Product ◽  
Functional Performance ◽  
Hydroxyl Groups ◽  
Aromatic Rings ◽  
Vis Spectroscopy ◽  
Phenolic Hydroxyl Groups ◽  
Rhus Vernicifera ◽  
Dyed Fabrics

Laccase from Rhus vernicifera was applied to catalyze the polymerization of gallic acid (GA) as a way of “in situ” dyeing and finishing for wool, silk, nylon, cotton and viscose fabrics. The laccase-catalyzed polymerization of GA was confirmed by the results of UV-vis spectroscopy and differential thermal analysis. The adsorption of the GA oxidation product on the fibers contributed to the color effect and functional performance of treated fabrics. The dyed fabrics exhibited gray colors with pale to medium shades, depending on fiber categories. All the dyed fabrics showed significantly enhanced UV protection performance and antioxidant activity, and the dyed wool and silk had obviously improved deodorizing ability. These improved functional properties were related to the increased quantity of aromatic rings, phenolic hydroxyl groups and carboxyl groups in the GA oxidation product adsorbed by fibers.

scholarly journals Study on the cleavage of alkyl-O-aryl bonds by in situ generated hydroxyl radicals on an ORR cathode

RSC Advances ◽  
2017 ◽  
Vol 7 (81) ◽  
pp. 51419-51425 ◽  
Author(s):  
Lei Wang ◽  
Yongmei Chen ◽  
Shuangyan Liu ◽  
Haomin Jiang ◽  
Linan Wang ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Active Sites ◽  
Bond Cleavage ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups

˙OH selectively attacks the active sites opposite to phenolic hydroxyl groups and leads to bond-cleavage of ether bonds.

Reactivity of syringyl quinone methide intermediates in dehydrogenative polymerization. Part 2: pH effect in horseradish peroxidase-catalyzed polymerization of sinapyl alcohol

Holzforschung ◽  
2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Yuki Tobimatsu ◽  
Toshiyuki Takano ◽  
Hiroshi Kamitakahara ◽  
Fumiaki Nakatsubo
Keyword(s):  
Horseradish Peroxidase ◽  
Uv Spectroscopy ◽  
Ph Effect ◽  
Water Soluble ◽  
Quinone Methide ◽  
Photodiode Array Detection ◽  
Sinapyl Alcohol ◽  
Acidic Conditions ◽  
Dehydrogenative Polymerization ◽  
Catalyzed Polymerization

Abstract The solvent pH effect in the horseradish peroxidase (HRP)-catalyzed polymerization of sinapyl alcohol (S-alc) and analogously, sinapyl alcohol γ-O-glucoside (isosyringin, iso-S) was investigated particularly focusing on the behavior of syringyl-type quinone methide intermediates (S-type QMs) under acidic conditions. At first, the HRP-catalyzed polymerization of iso-S at pH 6.5–2.5, which produces water-soluble dehydrogenation polymer (DHP) intermediates in a homogeneous phase, was monitored by UV spectroscopy and gel permeation chromatography with photodiode array detection (GPC-PDA). Under acidic conditions at pH below 4.5, unstablilized S-type QMs from iso-S are rapidly quenched resulting in efficient productions of DHPs, although substantial loss of HRP activity and the resulting insufficient polymerization were inevitable at pH below 3.5. In addition, it was found that a small addition of guaiacyl-type comonomer (isoconiferin, iso-G) effectively promotes the polymerization of iso-S under acidic conditions, in which the comonomer serves as a radical mediator to facilitate the HRP-catalyzed oxidations of iso-S. Next, the HRP-catalyzed polymerization of S-alc at various pH values was conducted and the resulting DHPs were characterized by GPC and NMR measurements. The yields of isolated DHPs significantly increased as solvent pH decreased below 4.5. The structural analyses of the DHPs demonstrated that reaction selectivity of S-type QMs during the polymerization drastically changed at pH below 4.5: they react efficiently with water molecules as solvent leading to the formation of benzyl alcohol type β-O-4 substructures preferentially to the formation of α-O-aryl type substructures. Consequently, the data in this study demonstrated that acidic conditions at pH below 4.5 are favored in the dehydrogenative polymerization of S-alc from the viewpoint of the reactivity of S-type QMs.

Determination of Phenolic Hydroxyl Groups in Lignin by Combined Use of 1H NMR and UV Spectroscopy

Holzforschung ◽  
1999 ◽  
Vol 53 (5) ◽  
pp. 529-533 ◽  
Author(s):  
Eija Tiainen ◽  
Torbjörn Drakenberg ◽  
Tarja Tamminen ◽  
Kirsi Kataja ◽  
Anneli Hase
Keyword(s):  
Uv Spectroscopy ◽  
Spectroscopic Properties ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Model Compounds ◽  
H Nmr ◽  
Combined Use ◽  
Phenolic Hydroxyl Groups ◽  
The Difference

Summary Two independent spectroscopic methods are presented and compared for the quantitation of the phenolic hydroxyl groups in lignins. The combined information is used to further elucidate the character of the lignin samples examined. The UV method is based on the difference of the spectroscopic properties of the ionised and the nonionised phenol. The method using 1H NMR spectroscopy is based on the exchange of phenolic protons in D2O. The difference in integrated proton intensities in the sample dissolved in DMSO and the sample with additional 20% D2O is proportional to the phenolic protons. The method based on UV spectroscopy uses differences in the maxima close to 300 nm and 350 nm of the sample dissolved in alkali and the neutral sample. The results using the two independent methods are in agreement for milled wood lignin, for kraft lignin and for model compounds carrying one aromatic hydroxyl group. For modified lignins and for model compounds with more than one aromatic hydroxyl group, the UV method gives too low values for phenolic hydroxyl groups. The combined results obtained by the two methods however provide information of the total amount of the phenolic groups and of the nature of the phenolic structure formed by the lignin refining.

The Study on Nano-Silica Modified Phenolic Resin Used as the Magnesite-Carbon Brick Binder

2012 ◽  
Vol 535-537 ◽  
pp. 1529-1533
Author(s):  
Qing Ling Liao ◽  
Li Ming Zeng ◽  
Xuan Ke Li
Keyword(s):  
Phenolic Resin ◽  
Sol Gel ◽  
Sio2 Nanoparticles ◽  
Hydroxyl Groups ◽  
Sol Gel Process ◽  
High Bulk Density ◽  
Phenolic Hydroxyl Groups ◽  
High Bulk ◽  
Nanosized Silica

The modified phenolic resin was synthesized by sol-gel process using in-situ formed nanosized silica. The improved phenolic resin was characterized by IR and TG-DTA analyses .The results show that the interaction between SiO2 nanoparticles and phenolic resin lead to the decrease of concentration of phenolic hydroxyl groups, and introduce the impurity atom Si to the phenolic resin molecule chain, which promotes the heat resistance and stability of phenolic resin. The physicochemical property analyses show that the magnesite-carbon brick using this modified phenolic resin as binder possesses a low apparent porosity and a high bulk density and compression strength.

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

Sign in / Sign up

Export Citation Format

Share Document