Reagent For Oxidation Research Articles

Unveiling the high-temperature dielectric response of text {Bi}_{0.5}text {Na}_{0.5}text {TiO}_{3}

Understanding the physics behind changes in dielectric permittivity and mechanical response with temperature and frequency in lead-free ferroic materials is a fundamental key to achieve optimal properties and to guarantee good performance in the technological applications envisaged. In this work, dense text {Bi}_{0.5}text {Na}_{0.5}text {TiO}_{3} (BNT) electroceramics were prepared through solid-state reaction of high-grade oxide reagents, followed by sintering at high temperature (1393 K for 3 h). In good agreement with previous reports in the literature, the thermal behaviour of dielectric response from these BNT materials showed the occurrence of a high-temperature diffuse-like permittivity peak, whose origin has been so far controversial. Thermally stimulated depolarization current, impedance and mechanical spectroscopies measurements were here conducted, over a wide range of temperature and frequency, to get a deep insight into the mechanism behind of this event. The approach included considering both as-sintered and reduced BNT samples, from which it is demonstrated that the broad high-temperature dielectric peak originates from interfacial polarization involving oxygen vacancies-related space-charge effects that develop at the grain-to-grain contacts. This mechanism, that contributes to the anomalous behavior observed in the mechanical response at low frequencies, could also be responsible for the presence of ferroelastic domains up to high temperatures.

Pretreatment of diesel-contaminated hydrophobic soil using surfactant and sodium hexa-metaphosphate (Na-HMP) to improve infiltration of aqueous phase remedial agents in unsaturated soil

The remediation of diesel-contaminated hydrophobic soil is difficult due to the inability of aqueous phase remedial agents to infiltrate the soil. This novel laboratory study enhanced the gravity-driven infiltration of water and oxidant solution into the hydrophobic soil by pretreatment. For this purpose, the hydrophobic soil was pretreated (partially liquid saturating) using 0.1% sodium hexa-metaphosphate (Na-HMP) and 0.5% alpha olefin sulfonate (AOS). The diesel-contaminated soil (34,167 ± 560 mg TPH/kg) was partially saturated with 0.5 pore volumes of Na-HMP and surfactant mixture solution. The infiltration experiment of the pretreated soil was conducted by pouring a solution (water/oxidant) provided from the Marriott reservoir over the digital balance. This study did not observe any natural infiltration of water or oxidant reagent into the diesel-contaminated soil. After the pretreatment, the cumulative infiltration of water to the pretreated soil increased to 5.17 cm after 40 min. The natural infiltration occurred due to the dispersion of soil particles and reduction of hydrophobicity by the Na-HMP and AOS, respectively. Widened soil pores were observed after pretreatment using the scanning electron microscopy (SEM) analysis. The infiltration of 5% Na2S2O8 solution was 5.80 cm after 40 min when the diesel-contaminated soil was pretreated with 0.1% Na-HMP and 0.5% AOS. Pretreatment using Na-HMP and AOS can enhance the remediation of highly hydrophobic and low-permeability soils. This finding can provide an insight into enhancing the soil remediation efficiency by increasing the gravity-driven uniform delivery of the remediation agent into the undisturbed soil. Graphical abstract

Evaluation of the Synthetic Scope and the Reaction Pathways of Proton-Coupled Electron Transfer with Redox-Active Guanidines in C-H Activation Processes.

Proton‐coupled electron transfer (PCET) is currently intensively studied because of its importance in synthetic chemistry and biology. In recent years it was shown that redox‐active guanidines are capable PCET reagents for the selective oxidation of organic molecules. In this work, the scope of their PCET reactivity regarding reactions that involve C−H activation is explored and kinetic studies carried out to disclose the reaction mechanisms. Organic molecules with potential up to 1.2 V vs. ferrocenium/ferrocene are efficiently oxidized. Reactions are initiated by electron transfer, followed by slow proton transfer from an electron‐transfer equilibrium.

Biocatalytic Strategy for Grafting Natural Lignin with Aniline.

This paper presents an enzyme biocatalytic method for grafting lignin (grafting bioprocess) with aniline, leading to an amino-derivatized polymeric product with modified properties (e.g., conductivity, acidity/basicity, thermostability and amino-functionalization). Peroxidase enzyme was used as a biocatalyst and H2O2 was used as an oxidation reagent, while the oxidative insertion of aniline into the lignin structure followed a radical mechanism specific for the peroxidase enzyme. The grafting bioprocess was tested in different configurations by varying the source of peroxidase, enzyme concentration and type of lignin. Its performance was evaluated in terms of aniline conversion calculated based on UV-vis analysis. The insertion of amine groups was checked by 1H-NMR technique, where NH protons were detected in the range of 5.01–4.99 ppm. The FTIR spectra, collected before and after the grafting bioprocess, gave evidence for the lignin modification. Finally, the abundance of grafted amine groups was correlated with the decrease of the free –OH groups (from 0.030 to 0.009 –OH groups/L for initial and grafted lignin, respectively). Additionally, the grafted lignin was characterized using conductivity measurements, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD-NH3/CO2) and scanning electron microscopy (SEM) analyses. The investigated properties of the developed lignopolymer demonstrated its disposability for specific industrial applications of derivatized lignin.

Rutheniumethynyl-Triarylamine Organic-Inorganic Mixed-Valence Systems: Regulating Ru-N Electronic Coupling by Different Aryl Bridge Cores.

Four rutheniumethynyl-triarylamine complexes 1-4 with different aryl bridge cores were prepared. The solid structures of complexes 2-4 were fully confirmed by X-ray single-crystal diffraction analysis. Two consecutive one-electron oxidation processes of complexes 1-4 were attributed to the ruthenium and nitrogen centers, as revealed by cyclic voltammetry and square-wave voltammogram. Results also showed decreasing potential difference ΔE of complexes 1, 3, and 4, with the largest value for 2. Upon chemical oxidation of complexes 1-4 by 1.0 eq oxidation reagents FcPF6 or AgSbF6 , the mixed-valence complexes, except for 2+ , show characteristic broad NIR absorptions in the UV-vis-NIR spectroscopic experiments. NIR multiple absorptions were assigned to NAr2 →RuCp*(dppe) intervalence charge transfer (IVCT) and metal-to-ligand charge transfer transitions by TDDFT calculations. Coupling parameter (Hab ) from Hush theory revealed that increasing electronic communication in 1+ , 3+ , and 4+ . Electron density distribution of the HOMO for neutral molecules (1, 3, and 4) and spin density distribution of the corresponding single-oxidized states (1+ , 3+ , and 4+ ) increases progressively on the bridge as the size of the aromatic system increases, proving incremental contributions from bridge cores during oxidation.

Novel Si(II)+ and Ge(II)+ Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction

Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of <0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4–, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4–, Cp*Ge:+B(SiCl3)4–, and [Cp(SiMe3)3Ge:+]B(SiCl3)4–.

Base-Mediated Oxidative Degradation of Secondary Amides Derived from p-Amino Phenol to Primary Amides in Drug Molecules

One of the most common functional groups encountered in drug molecules is the amide, and the most common degradation pathway for amides is base-mediated hydrolysis to its constituent amine and carboxylic acid. Herein, we report for the first time, a base-mediated oxidative degradation pathway of secondary amides to primary amides. This transformation also represents a novel synthetic methodology, reported for the first time in this work, in transforming secondary amides to primary amides without using any oxidative reagents. The introduction of this mechanism into the pharmaceutical literature is important given that the mechanism and required reactants are present to carry out the chemistry in dosage forms.

An in-house UV-photolysis setup for the rapid degradation of both cationic and anionic dyes in dynamic mode through UV/H2O2-based advanced oxidation process

ABSTRACT A simple in-house UV-photolysis setup was utilised in dynamic mode for the degradation of cationic (methylene blue, rhodamine B and crystal violet) and anionic (congo red, methyl orange and acid red 27) dyes using H2O2 as an oxidising reagent. The methodology was optimised by using methylene blue and acid red 27 as representatives of cationic and anionic dyes, respectively. The optimisation process involved the study of the following critical parameters: concentration of dye and H2O2 and sample flow rate for achieving complete and instantaneous degradation of dye. Using the experimental conditions established during optimisation, at a concentration of H2O2 (0.03% (v/v) dye concentration of 50 µg mL−1 and a sample flow rate of 6 mL min−1, it was possible for complete degradation (>99%) of dye compounds. TOC and COD values of treated samples were decreased to about 79% and 91%, respectively after second UV-photolysis/H2O2 treatment indicating the considerable degradation of dyes was occurred during UV-photolysis process. In addition, studies on the effect of various ions Na+, K+, Ca2+, Mg2+, Fe3+, Cl−, NO3 −, SO4 2-, PO4 3- and CO3 2- that are normally present in dye effluents were carried out and the results indicated that these ions had no significant effect on the degradation efficiency of dyes. The developed procedure was finally applied to real textile wastewater which was degraded very effectively (>99%) indicating that the developed UV-photolysis setup has high potential for commercial scale applications.

Symmetrical dimethylation of H4R3: A bridge linking DNA damage and repair upon oxidative stress

The DNA lesions caused by oxidative damage are principally repaired by the base excision repair (BER) pathway. 8-oxoguanine DNA glycosylase 1 (OGG1) initiates BER through recognizing and cleaving the oxidatively damaged nucleobase 8-oxo-7,8-dihydroguanine (8-oxoG). How the BER machinery detects and accesses lesions within the context of chromatin is largely unknown. Here, we found that the symmetrical dimethylarginine of histone H4 (producing H4R3me2s) serves as a bridge between DNA damage and subsequent repair. Intracellular H4R3me2s was significantly increased after treatment with the DNA oxidant reagent H2O2, and this increase was regulated by OGG1, which could directly interact with the specific arginine methyltransferase, PRMT5. Arginine-methylated H4R3 could associate with flap endonuclease 1 (FEN1) and enhance its nuclease activity and BER efficiency. Furthermore, cells with a decreased level of H4R3me2s were more susceptible to DNA-damaging agents and accumulated more DNA damage lesions in their genome. Taken together, these results demonstrate that H4R3me2s can be recognized as a reader protein that senses DNA damage and a writer protein that promotes DNA repair.

Formation of nitrophenolic byproducts in soils subjected to sulfate radical oxidation

Activated persulfate oxidation is an emerging technology with great prospects for soil remediation. For the first time, the present study demonstrated that application of this technology to soils with nitrite (NO2−) presence yielded nitrophenolic byproducts, including 3-nitrophenol, 4-nitrophenol, 2-hydroxy-5-nitrobenzoic acid, and 4-hydroxy-3-nitrobenzoic acid. Their yields were positively related to the contents of soil organic matter (SOM). Most of these byproducts were distributed in soil waters, suggesting that they are readily transported to other places, thus can contaminate a larger area. Nitrated byproducts presumably formed by oxidation of NO2− by SO4−, which generates NO2. This generated NO2 then reacted with phenolic moieties in SOM and was transformed to organic nitrogen. In addition, ammonia nitrogen in soils was oxidized by SO4− and contributed to the formation of nitrophenolic byproducts. Considering the omnipresence of nitrite and ammonia in subsurface soils, this study identified potential risks of persulfate use for in situ soil remediation. These results are relevant to devise strategies to avoid inappropriate use of oxidative reagents and the resulting formation of toxic byproducts.

Effect of Pre-reduction Degree on Softening Behavior of Simulant Sinter Iron Ore

Reduction test under load is normally applied to evaluate softening and melting behaviour of ferrous burdens at simulated condition in cohesive zone in blast furnace. Outcomes from this test are very complex because they depend on reduction degree, chemical composition, basicity, melts physical property, etc. One of the reasons to make complex this test is sample for the test provided as particle packed bed. In order to comprehend softening and melting behaviour of cohesive zone, focus on behaviour of single particle as a component of particle packed bed in this study. For simplification, a pre-reduced simulant sinter iron ore was prepared as single tablet sample. The samples were made from mixture of reagent oxides and they were pre-reduced to control their reduction degree to several reduction levels. The tablet sample was rapidly heated up to 900°C, and then gradually heated up with 10°C/min under inert gas atmosphere and 0.1 MPa load. Shrinkage degree of the sample was measured during the softening and melting test, and quenched sample was made at certain temperature when the sample shows a characteristic tendency. Cross-sectioning observation of the quenched sample provided mineral phases distribution in the tablet sample. The observation indicated that peripheral structure has a significant effect on deformation resistance. Especially in there, existence of molten slag phase could make easy to deform the sample particle shape, and metallic solid Fe phase helped to strengthen the particle’s deformation resistance.

Application of trityl moieties in chemical processes: part I

Triphenylcarbenium ions (trityl cations: [RPh]3C+) are broadly identified organic compounds, because of their several uses, such as protective group, a catalyst for C–C bond formation, dye chemistry, carbohydrate chemistry, oxidation and reduction reagent, polymer and peptide synthesis, chiral catalyst, activity-based probes, and photochemical reactions. Trityl cations have also been applied as neutral Lewis acids in different chemical reactions. Possibly, the trityl cation is most widely used in hydride abstraction reactions both in the study of mechanisms transformations (organometallic and organic) and in organic syntheses. Ph3C+ is also extensively applied as very efficient activators and as one-electron oxidants for olefin polymerization reactions. In this review, we explain applications of trityl moieties in chemical processes and synthesis.

Multistage Self-Assembly Strategy: Designed Synthesis of N-doped Mesoporous Carbon with High and Controllable Pyridine N Content for Ultrahigh Surface-Area-Normalized Capacitance

Nitrogen doping could improve the performance of carbon materials in electrocatalysis, CO2 adsorption, and energy storage. [1]However, the control of the doping type and the amount of nitrogen (N)-...

Metallic Pt and PtOx dual-cocatalyst-loaded WO3 for photocatalytic production of peroxydisulfate and hydrogen peroxide

Photocatalytic production of green oxidation reagents as an economical and environmental-friendly process is a promising strategy to replace the traditional production processes. In the present study, a series of 1.0 wt% Pt/WO3 photocatalysts with different surface chemical states of Pt were successfully fabricated. The different surface metallic Pt (Pt0) and oxidized Pt (PtOx) ratios on WO3 showed significant effects on the photocatalytic activities for strong oxidants of peroxydisulfate ( $$ {\text{S}}_{ 2} {\text{O}}_{8}^{2 - } $$ ) and hydrogen peroxide (H2O2) formations. It is proposed that surface Pt0 and PtOx functioned as reduction site for O2 reduction to H2O and oxidation site for H2O oxidation to H2O2, respectively, during the photocatalytic process. As a result, a higher surface composition of Pt0 prepared using photodeposition (PD) method led to the formation of higher amount of $$ {\text{S}}_{ 2} {\text{O}}_{8}^{2 - } $$ . On the other hand, PtOx-loaded WO3 using impregnation (IM) method showed significant formations of $$ {\text{S}}_{ 2} {\text{O}}_{8}^{2 - } $$ and H2O2 simultaneously. This work provided a new idea for the design of noble metal Pt-supported WO3 for efficiently photocatalytic generation of $$ {\text{S}}_{ 2} {\text{O}}_{8}^{2 - } $$ and H2O2.

Treatment Technology of Difficult-Biodegradable Printing and Dyeing Waste-Water

The pollution of printing and dyeing waste-water mainly comes from dyes. In the process of printing and dyeing, different dyeing processes produce different pollutants, resulting in the difference of their properties. The treatment of printing and dyeing waste-water, according to the difference of technical principles, mainly includes seven treatment technologies: physical method, biochemistry method, physical chemistry method, ozone oxidation method, Fenton reagent oxidation method, photocatalytic oxidation method and wet (catalytic) oxidation method. Different treatment methods are used for waste-water with different properties and concentrations. Biochemical decomposition of organic matter in waste-water by microbial metabolism is a common method for the treatment of printing and dyeing waste-water.

Prussian blue/PVDF catalytic membrane with exceptional and stable Fenton oxidation performance for organic pollutants removal

Catalytic membranes as heterogeneous advanced oxidation microreactors are appealing for persistent organic pollutants (Pops) treatment. Constructing a robust catalytic membrane with highly active sites for instantaneous and standing mineralization of flowing Pops are challenging in its practical application. Herein, we enable in-situ growth and firm enchasing of Prussian blue (PB) micro-crystals in the micro-clusters of Polyvinylidene fluoride (PVDF) membrane, where active sites are fully exposed for oxidant reagent and target contaminants. The designed PB@PVDF catalytic membrane demonstrates exceptional efficiency for instantaneous degradation of recalcitrant organic molecules e.g. bisphenol A, methylene blue, rhodamine B as well as humic acid. The membrane maintains high removal efficiency above 99% for MB with a constant flux of 300 L m−2 h−1 during a long-term (24 h) cross-flow test. Both the enrichment of radials and pollutants in confined tortuous micro-pores and prompt flowing away of degraded products lead to the superior catalytic activity of heterogeneous Fenton reactors.

The bZIP Transcription Factor AflRsmA Regulates Aflatoxin B1 Biosynthesis, Oxidative Stress Response and Sclerotium Formation in Aspergillus flavus.

Fungal secondary metabolites play important roles not only in fungal ecology but also in humans living as beneficial medicine or harmful toxins. In filamentous fungi, bZIP-type transcription factors (TFs) are associated with the proteins involved in oxidative stress response and secondary metabolism. In this study, a connection between a bZIP TF and oxidative stress induction of secondary metabolism is uncovered in an opportunistic pathogen Aspergillus flavus, which produces carcinogenic and mutagenic aflatoxins. The bZIP transcription factor AflRsmA was identified by a homology research of A. flavus genome with the bZIP protein RsmA, involved in secondary metabolites production in Aspergillus nidulans. The AflrsmA deletion strain (ΔAflrsmA) displayed less sensitivity to the oxidative reagents tert-Butyl hydroperoxide (tBOOH) in comparison with wild type (WT) and AflrsmA overexpression strain (AflrsmAOE), while AflrsmAOE strain increased sensitivity to the oxidative reagents menadione sodium bisulfite (MSB) compared to WT and ΔAflrsmA strains. Without oxidative treatment, aflatoxin B1 (AFB1) production of ΔAflrsmA strains was consistent with that of WT, but AflrsmAOE strain produced more AFB1 than WT; tBOOH and MSB treatment decreased AFB1 production of ΔAflrsmA compared to WT. Besides, relative to WT, ΔAflrsmA strain decreased sclerotia, while AflrsmAOE strain increased sclerotia. The decrease of AFB1 by ΔAflrsmA but increase of AFB1 by AflrsmAOE was on corn. Our results suggest that AFB1 biosynthesis is regulated by AflRsmA by oxidative stress pathways and provide insights into a possible function of AflRsmA in mediating AFB1 biosynthesis response host defense in pathogen A. flavus.

Characterization of cannonball jellyfish (Stomolophus sp. 2) blue protein: a pH-stable pigment.

Pigments are present in a broad variety of terrestrial and aquatic organisms. The cannonball jellyfish (Stomolophus sp. 2) is an important fishery resource in the northwest of Mexico and is processed to be traded and consumed as seafood. During the process, water with a soluble blue pigment and other compounds are discarded to the environment. In this work, we present some properties of the blue pigment from Stomolophus sp.2 (S2bp), to decide if it could be considered as a potential value-added waste and avoid the blue proteinaceous pigment wastewater. S2bp was purified to homogeneity and had a molecular mass of 28.0kDa; this protein exhibited a ʎmax at 650nm, contained Zn2+ and Cu2+ metal ions, and was stable from 10 to 50°C and in a pH range of 3.0 to 13.0 for 1h. It had halotolerant characteristics maintaining the blue coloration in a broad range of ionic strength (0-4M NaCl) and showed changes in ʎmax with chaotropic salts. In addition, S2bp was stable in the presence of organic acids and EDTA and in zwitterionic, anionic, and nonionic detergents at critical micellar concentration. However, oxidant reagents like NaClO and H2O2 decrease the coloration. These results show that the jellyfish pigment is a stable protein which makes it an alternative pigment for the food industry.

Oxidation of Thiol Using Ionic Liquid-Supported Organotelluride as a Recyclable Catalyst

Organotellurium compounds are known to be useful oxidation reagents. For developing a recoverable and reusable reagent, this paper describes the use of an ionic liquid (IL) support for the organotellurium reagent and its application as a recyclable catalyst for thiol oxidation. We have successfully prepared a novel diphenyl telluride derivative 5 bearing an imidazolium hexafluorophosphate group in its structure. It is found that the IL-supported diphenyl telluride 5 efficiently catalyzed the aerobic oxidation of various thiols in [bmim]PF6 solution under photosensitized conditions to provide the corresponding disulfides in excellent yields. The product can be isolated by simple ether extraction. The IL-supported catalyst 5 remaining in the ionic liquid phase can be reused for five successive runs while retaining high catalytic activity (97% yield even in the fifth run).

A dimeric stilbene extract produced by oxidative coupling of resveratrol active against &lt;em&gt;Plasmopara viticola&lt;/em&gt; and &lt;em&gt;Botrytis cinerea&lt;/em&gt; for vine treatments

Aim: Stilbenes are a group of polyphenols that contribute to the defense mechanisms of grapevine under stress conditions. The main active compounds are oligomeric stilbenes. The sourcing of such compounds is limited by plant raw material availability. In order to overcome this limitation, we proceeded to hemisynthesis of oligomeric stilbenes from natural resveratrol by oxidative coupling using metals. The reaction mixture and the obtained pure compounds were tested for their antimicrobial activity in vitro against P. viticola and B. cinerea, and compared with that of resveratrol and grapevine cane extract.Methods and results: Hemisynthesis was achieved in methanol using silver acetate (AgOAc) as oxidative coupling reagent. Four main compounds were obtained in the reaction mixture: δ-viniferin, parthenostilbenin B, oxistilbenins A and B. Results demonstrate the ability of oxidative coupling reaction to produce potent inhibitors of P. viticola and B. cinerea. The reaction mixture is enriched in antimicrobial compounds with high potency as it is at least eight times more active than grapevine cane extract against P. viticola. In addition, this reaction mixture reveals a high fungitoxicity against B. cinerea in contrast to the grapevine extract.Conclusion: The present findings indicate that metals could be used for producing highly antimicrobial compounds from natural resveratrol.Significance and impact of the study: In this study, a method to produce active dimeric stilbenes to protect grapevine was developed based on botanical ingredients. The combination of natural extracts, rich in resveratrol, and metals such as copper may be used as alternatives to Bordeaux mixture and chemical fungicides to protect crops.