On the Significance of the Superoxide Radical () in Oxidative Delignification, Studied with 4-<i>t</i>-Butylsyringol and 4-<i>t</i>-Butylguaiacol. Part I. The Mechanism of Aromatic Ring Opening

Gierer, Josef; Yang, Erquan; Reitberger, Torbjörn

doi:10.1515/hfsg.1994.48.5.405

Cited by 53 publications

(22 citation statements)

References 18 publications

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“…In the absence of a stabilizing agent, transition metal catalyzed hydrogen peroxide decomposition leads to the generation of various oxidative species (Gratzl 1990). Recently, the reactions of these oxidative radical species with simple lignin model compounds have been studied and certain features of their specificity have been disclosed (Gierer et al 1992;Gierer et al 1994). However, the presence of these oxidative radicals makes it virtually impossible to ascertain the reaction mechanisms of hydrogen peroxide.…”

Section: Resultsmentioning

confidence: 99%

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Kadla¹,

Chang²,

Jameel³

1999

Holzforschung

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A technical pine kraft lignin was subjected to alkaline hydrogen peroxide oxidation in the presence of DTMPA and molecular oxygen at various temperatures. In the presence of DTMPA the lignin was found to undergo increasing levels of oxidation and degradation with increasing temperature. At 110°C over 80 % of the kraft lignin was degraded. Analyses of the degraded lignins indicated that both phenolic and nonphenolic lignin moieties were degraded. At 90°C the addition of molecular oxygen resulted in further lignin demethoxylation, but did not decrease the amount of phenolic hydroxyl groups or hydrogen peroxide consumed. In the absence of DTMPA the hydrogen peroxide was rapidly degraded, and accompanied by only minimal lignin oxidation.

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Section: Resultsmentioning

confidence: 99%

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Kadla¹,

Chang²,

Jameel³

1999

Holzforschung

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“…Besides their role in extending the kind and number of lignin units that can be oxidized by the action of laccase, natural mediators are important because ligninolytic enzymes have to act indirectly during the early phases of plant cell wall degradation due to size exclusion limitations (13,14). Other small molecular agents participating in lignin degradation and produced directly or indirectly by ligninolytic enzymes include manganic ion (Mn 3ϩ ) (24,27,50), the cationic radical of the fungal metabolite veratryl (3,4-dimethoxybenzyl) alcohol (26), and activated oxygen species such as the hydroxyl radical (HO ⅐ ) and superoxide anion radical (O 2 ⅐Ϫ ) (2,15,27). Except for O 2 ⅐Ϫ , all of these compounds are able to oxidize lignin units.…”

mentioning

confidence: 99%

“…However, the O 2 ⅐Ϫ produced by white-rot fungi (12) can participate in the production of H 2 O 2 via both dismutation ( (4). Furthermore, by reacting with phenoxyl radicals produced from lignin model compounds, it can result in oxidative degradation being favored over coupling reactions (15).…”

mentioning

confidence: 99%

Oxygen Activation during Oxidation of Methoxyhydroquinones by Laccase from Pleurotus eryngii

Guillén

Muñoz

Gómez-Toribio

et al. 2000

Appl Environ Microbiol

105

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Oxygen activation during oxidation of the lignin-derived hydroquinones 2-methoxy-1,4-benzohydroquinone (MBQH 2 ) and 2,6-dimethoxy-1,4-benzohydroquinone (DBQH 2 ) by laccase from Pleurotus eryngii was examined. Laccase oxidized DBQH 2 more efficiently than it oxidized MBQH 2 ; both the affinity and maximal velocity of oxidation were higher for DBQH 2 than for MBQH 2 . Autoxidation of the semiquinones produced by laccase led to the activation of oxygen, producing superoxide anion radicals (

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“…Less HOO -was produced in PMg(OH)2 bleaching than that in PNaOH bleaching (Yun and He 2013). Therefore, PMg(OH)2 bleaching produced less hydroquinone and quinone than that of PNaOH bleaching (Gierer et al 1994). Furthermore, PMg(OH)2 bleaching produced less oxygen and hydroxyl radicals than that of PNaOH bleaching, which meant that less new quinones had been produced (Agnemo and Gellerstedt 1979).…”

Section: Spectra Analysis Before and After Irradiationmentioning

confidence: 97%

Photo-induced Yellowing of Mg(OH)2-based Peroxide Bleached Deinked Pulp

Yun¹,

2017

BioResources

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The effects of ultraviolet (UV) irradiation on the changes in color and chemical structure of the surfaces of unbleached, PNaOH-, and PMg(OH)2-bleached deinked pulp (DIP) were studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of color changes in pulp surfaces during the photo yellowing was performed by measuring the brightness loss, post color (PC) number, and CIELAB parameters (L*, a*, b*, and ΔE*). The results showed that the pulp brightness loss, PC number, and chromatic aberration had a linear relationship with b*. During the UV irradiation, the pulp brightness loss, PC number, and chromatic aberration (ΔE*) increased quickly, and then the changes slowed down. After being irradiated with UV for 360 min, the band intensity of the pulps at 1729 cm -1 increased distinctively and a new band at 1674 cm -1 appeared. This indicated that p-quinone groups were produced during the irradiation process, thus resulting in paper yellowing. The band intensity at 1674 cm -1 of PMg(OH)2-bleached pulp was lower than that of PNaOH-bleached pulp, which indicated that the brightness stability of PMg(OH)2 pulp was better than that of PNaOH pulp.

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On the Significance of the Superoxide Radical () in Oxidative Delignification, Studied with 4-t-Butylsyringol and 4-t-Butylguaiacol. Part I. The Mechanism of Aromatic Ring Opening

Cited by 53 publications

References 18 publications

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Oxygen Activation during Oxidation of Methoxyhydroquinones by Laccase from Pleurotus eryngii

Photo-induced Yellowing of Mg(OH)2-based Peroxide Bleached Deinked Pulp

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