Evidence for superoxide-radical anion, singlet oxygen and OH-radical intervention during the degradation of the lignin model compound (3-methoxy-4-hydroxyphenylmethylcarbinol)

2005 ◽  
Vol 169 (3) ◽  
pp. 271-278 ◽  
Author(s):  
P. Raja ◽  
A. Bozzi ◽  
H. Mansilla ◽  
J. Kiwi
Keyword(s):  
Singlet Oxygen ◽  
Radical Anion ◽  
Model Compound ◽  
Superoxide Radical ◽  
Oh Radical ◽  
Superoxide Radical Anion ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Radical Intervention

Photoinduced Superoxide Radical Anion and Singlet Oxygen Generation in the Presence of Novel Selenadiazoloquinolones (An EPR Study)

2010 ◽  
Vol 87 (1) ◽  
pp. 32-44 ◽  
Author(s):  
Zuzana Barbieriková ◽  
Maroš Bella ◽  
Juraj Kučerák ◽  
Viktor Milata ◽  
Soňa Jantová ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Superoxide Radical Anion ◽  
Oxygen Generation ◽  
Singlet Oxygen Generation

scholarly journals The Reactive Oxygen Species Singlet Oxygen, Hydroxy Radicals, and the Superoxide Radical Anion—Examples of Their Roles in Biology and Medicine

Oxygen ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 77-95
Author(s):  
Ruth Edge ◽  
T. George Truscott
Keyword(s):  
Reactive Oxygen Species ◽  
Singlet Oxygen ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Reactive Oxygen ◽  
High Energy ◽  
Oxygen Species ◽  
Superoxide Radical Anion ◽  
Hydroxy Radicals ◽  
Electronically Excited

Reactive oxygen species comprise oxygen-based free radicals and non-radical species such as peroxynitrite and electronically excited (singlet) oxygen. These reactive species often have short lifetimes, and much of our understanding of their formation and reactivity in biological and especially medical environments has come from complimentary fast reaction methods involving pulsed lasers and high-energy radiation techniques. These and related methods, such as EPR, are discussed with particular reference to singlet oxygen, hydroxy radicals, the superoxide radical anion, and their roles in medical aspects, such as cancer, vision and skin disorders, and especially pro- and anti-oxidative processes.

Radiolysis of Tertiary Butyl Hydroperoxide in Aqueous Solution. Reductive Cleavage by the Solvated Electron, the Hydrogen Atom, and, in Particular, the Superoxide Radical Anion

1990 ◽  
Vol 45 (10) ◽  
pp. 1425-1432 ◽  
Author(s):  
Shailesh Phulkar ◽  
Balijepalli Sethu Madhava Rao ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Hydrogen Atom ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Maximum Yield ◽  
Branching Ratio ◽  
Main Reaction ◽  
Oh Radical ◽  
Solvated Electron ◽  
Tertiary Butyl ◽  
Superoxide Radical Anion

The reactions of the solvated electron, the H atom, the OH radical and the superoxide radical anion with t-butylhydroperoxide (t-BuOOH) have been studied in aqueous solutions using γ-radiolysis and pulse radiolysis to generate these radicals.The solvated electron reacts rapidly with t-BuOOH (k=5 × 109dm3mol-1 s-1) yielding t-BuO· and ·OH in a ratio of 4:1. The yield of t-BuO· has been determined by measuring its fragmentation product, acetone.The H atom reacts more slowly with t-BuOOH (k=5 × 10 7 dm3 mol-1 s-1). There is very little H-abstraction from the methyl and the hydroperoxyl groups (about 3%), the main reaction again being the scission of the hydroperoxyl function with a branching ratio t-BuO·/·OH of about unity.The OH radical reacts with t-BuOOH considerably more slowly (k=8 × 10 7 dm3 mol-1 s-1) than with t-butanol (k=5 × 108 dm3 mol-1 s-1) with an approximate preference of 8:1 of abstracting a methyl hydrogen over a hydroperoxyl hydrogen atom. The carbon-centered radical undergoes γ-cleavage (k ≈ 102 s-1) thereby reforming an OH radical. The resulting chain reaction is rather short (maximum yield G(2-methyl-1,2-epoxypropane), 26 × 10-7 mol J-1 at low dose rate) due to H-abstraction at the hydroperoxyl function of t-BuOOH by the OH radical.The superoxide radical anion also reacts with t-BuOOH by cleaving the hydroperoxyl function. Its reactivity is, however, rather low (k=5 dm3 mol-1 s-1)

scholarly journals Revisiting the mechanism of β-O-4 bond cleavage during acidolysis of lignin VII: acidolyses of non-phenolic C6-C2-type model compounds using HBr, HCl and H2SO4, and a proposal on the characteristic action of Br− and Cl−

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Qiaoqiao Ye ◽  
Tomoya Yokoyama
Keyword(s):  
Model Compound ◽  
Bond Cleavage ◽  
Type Model ◽  
Enol Ether ◽  
Lignin Model Compound ◽  
Benzyl Cation ◽  
Acid Type ◽  
Unstable Compound ◽  
Lignin Model ◽  
Acidolysis Reaction

AbstractA non-phenolic C6-C2-type lignin model compound with the β-O-4 bond, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (I), was acidolyzed in aqueous 82% 1,4-dioxane containing HBr, HCl, or H2SO4 with a concentration of 0.2 mol/L at 85 ℃ to examine the differences between these acidolyses. Compound I primarily converted to an enol ether compound, 1-(2-methoxyphenoxy)-2-(3,4-dimethoxyphenyl)ethene (II), via the benzyl cation followed by acidolytic β-O-4 bond cleavage regardless of the acid-type, although the disappearance rates of compound I were remarkably different (HBr > HCl >> H2SO4). Acidolyses of compound II using these acids under the same conditions showed a similar tendency, but the rate differences were much smaller than in the acidolyses of compound I. Acidolyses of the α-methyl-etherified derivative of compound I (I-α-OMe) using these acids under the same conditions suggested that the formation rates of the benzyl cation from compound I-α-OMe (also from compound I) are not largely different between the acidolyses using these acids, but those of compound II from the benzyl cation are remarkably different. Acidolysis of the α-bromo-substituting derivative of compound I (I-α-Br) using HBr under the same conditions showed a characteristic action of Br¯ in the acidolysis. Br¯ adds to the benzyl cation generated from compound I or I-α-OMe to afford unstable compound I-α-Br, resulting in acceleration of the formation of compound II and of the whole acidolysis reaction.

scholarly journals Model compounds-based study on adsorption and dispersion properties of lignin-based superplasticizer

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098062
Author(s):  
Shuangping Ma ◽  
Qingjun Ding ◽  
Fen Zhou ◽  
Huaxiong Zhu
Keyword(s):  
Molecular Structure ◽  
Zeta Potential ◽  
Model Compound ◽  
Research Work ◽  
Structure Activity Relationship ◽  
Activity Relationship ◽  
Lignin Model Compound ◽  
Structure Activity ◽  
Lignin Model ◽  
Relationship Of

The chemical modifications of lignin-based superplasticizers have attracted extensive attentions during recent years. The comprehending of the structure-activity relationship of lignin-based superplasticizer is important to promote the modification and application research of lignin resources. However, lignin features complex and variable molecular structure, which is not conducive to study on structure-activity relationship of lignin-based superplasticizer as well as development and application of new lignin-based superplasticizer. However, the related research work can be simplified by selecting small molecular compound with appropriate molecular structure as the lignin model compound. This article intends to study the structure-activity relationship of lignin-based superplasticizer by using dihydroeugenol as the lignin model compound. Through the substitution of lignin by dihydroeugenol during the synthesis process, a model compound lignin-based superplasticizer (DAFS) was synthesized. The adsorption and dispersion properties of this superplasticizer and reference sample (LAFS) were investigated by fluidity test, Zeta-potential measurement, Total organic carbon analysis and others. The results suggest that the adsorption behavior of both DAFS and LAFS conformed to the Langmuir isotherms and Pseudo-second order kinetic. In cement paste, added with 1 g/L of LAFS and DAFS, Zeta potential were reduced from +3.5 to −15.2 mV and −18.7 mV, respectively. The substitution of lignin by dihydroeugenol has no significantly influence on the dispersive property, but differences on rheological properties which need to be optimized in the future. All the tests confirmed that dihydroeugenol is suitable to replace lignin on exploring the structure-activity relationship of lignin-based superplasticizer. This research work provides new insight on model study of lignin-based superplasticizer.

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