Reagent For Oxidation Research Articles

Gated photochromic molecules with AIEgen: turn-on the photochromism with an oxidation reagent.

A couple of gated photochromic molecules TrPEP and TrPEPO with AIEgen have been rationally designed and synthesized. No photochromism is detected for TrPEP whilst TrPEPO shows obvious photochromic properties in the solution state. By adding equimolar H2O2 aqueous solution to the TrPEP solution, the photochromic properties would be quickly turned on. The oxidation reagent acts as a gate to switch the photochromic properties by switching the triphenylphosphine group to a triphenylphosphine oxide group. Both TrPE and TrPEO display typical AIE phenomena. Different intensive emission bands with the emission maxima of 500 nm and 455 nm are detected before (TrPEP) and after (TrPEPO) oxidization in solid states. Combining the AIEgens, photochromic ON/OFF states can be easily indicated by the different emission colors in the solid state. Single crystal analyses and TD-DFT calculations were carried out to further investigate the photophysical and photochromic properties of these compounds. These new triphenylethylene derivatives provide a new strategy to achieve gated photochromic materials with simple chemical structures and gate indicators.

Clock mediates liver senescence by controlling ER stress.

Accumulated evidence indicates that circadian genes regulate cell damage and senescence in most mammals. Endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) regulate longevity in many organisms. However, the specific mechanisms of the relationship between the circadian clock and the two stress processes in organisms are poorly understood. Here, we show that Clock-mediated Pdia3 expression is required to sustain reactive oxidative reagents and ER stress. First, ER stress and ROS are strongly activated in the liver tissue of ClockΔ19 mutant mice, which exhibit a significant aging phenotype. Next, transcription of Pdia3 is mediated by the circadian gene Clock, but this process is affected by the ClockΔ19 mutant due to the low affinity of the E-box motif in the promoter. Finally, ablation of Pdia3 with siRNA causes ER stress with sustained phosphorylation of PERK and eIF1α, resulting in exaggerated up-regulation of UPR target genes and increased apoptosis as well as ROS. Moreover, the combined effects result in an imbalance of cell homeostasis and ultimately lead to cell damage and senescence. Taken together, this study identified the circadian gene Clock as a regulator of ER stress and senescence, which will provide a reference for the clinical prevention of aging.

The Palladium Acetate-Catalyzed Microwave-Assisted Hirao Reaction without an Added Phosphorus Ligand as a "Green" Protocol: A Quantum Chemical Study on the Mechanism.

It was proved by our experiments that on microwave irradiation, the mono‐ or bidentate phosphorus ligands generally applied in the palladium(II)‐catalyzed P–C coupling reaction of aryl bromides and dialkyl phosphites or secondary phosphine oxides may be substituted by the excess of the >P(O)H reagent that exists under a tautomeric equilibrium. Taking into account that the reduction of the palladium(II) salt and the ligation of the palladium(0) so formed requires 3 equivalents of the P‐species for the catalyst applied in a quantity of 5–10%, all together, 15–30% of the P‐reagent is necessary beyond its stoichiometric quantity. In the coupling reaction of diphenylphosphine oxide, it was possible to apply diethyl phosphite as the reducing agent and as the P‐ligand. The reactivities of the diethyl phosphite and diphenylphosphine oxide reagents were compared in a competitive reaction. The mechanism and the energetics of this new variation of the Hirao reaction of bromobenzene with Y2P(O)H reagents (Y=EtO and Ph) was explored by quantum chemical calculations. The first detailed study on simple reaction models justified our assumption that, under the conditions of the reaction, the trivalent form of the >P(O)H reagent may serve as the P‐ligand in the palladium(0) catalyst, and shed light on the fine mechanism of the reaction sequence. The existence of the earlier described bis(palladium complex) {[H(OPh2P)2PdOAc]2} was refuted by high level theoretical calculations. This kind of complex may be formed only with chloride anions instead of the acetate anion. The interaction of palladium acetate and Y2P(O)H may result in only the formation of the [(HO)Y2P]2Pd complex that is the active catalyst in the Hirao reaction. The new variation of the Hirao reaction is of a more general value, and represents the greenest protocol, as there is no need for the usual P‐ligands. Instead, the >P(O)H reagent should be used in an excess of up to 30%. Hence, the costs and environmental burdens may be decreased.

Treatment of textile dyeing industry effluent using hydrodynamic cavitation in combination with advanced oxidation reagents

Treatment of textile dyeing industry (TDI) effluent was investigated using hydrodynamic cavitation (HC) and in combination with advanced oxidation reagents such as air, oxygen, ozone and Fenton’s reagent. Slit venturi was used as the cavitating device in HC reactor. The effects of process parameters such as inlet pressure, cavitation number, effluent concentration, ozone and oxygen flow rate, loading of H2O2 and Fenton’s reagent on the extent of reduction of TOC, COD and color were studied. Efficiency of the hybrid treatment processes were evaluated on the basis of their synergetic coefficient. It was observed that almost 17% TOC, 12% COD, and 25% color removal was obtained using HC alone at inlet pressure of 5bar and pH of 6.8. The rate of reduction of TOC and COD decreased with dilution of the samples. HC in combination with Fenton’s reagent (FeSO4·7H2O:H2O2 as 1:5) was most effective with reduction of 48%TOC and 38% COD in 15min and 120min respectively with almost complete decolorization (98%) of the TDI effluent. Whereas HC in combination with oxygen (2L/min) and ozone (3g/h) produced reduction of 48% TOC, 33% COD, 62% decolorization and 48% TOC, 23% COD, 88%, decolorization of TDI effluent respectively.

Heterocyclization of carboxy- and sulfonamides in the course of oxidative addition to unsaturated substrates

Formation of heterocyclic compounds in the course of oxidative addition of carboxamides and sulfonamides to alkenes and dienes is reviewed. Main attention is focused on reactions proceeding in the presence of halo-containing oxidative systems and reagents. Features of behavior of fluorine-substituted sulfonamides and carboxamides are discussed.

Cu(OAc)2 /TEMPO Cooperative Promoted Hydroamination Cyclization and Oxidative Dehydrogenation Cascade Reaction of Homopropargylic Amines.

A novel and efficient Cu(OAc)2 -catalyzed hydroamination cyclization and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidative dehydrogenation cascade reaction of homopropargylic amines has been developed. A library of 1,2-disubstituted pyrrole derivatives were obtained in good-to-high yields in one pot with no step-by-step feeding process. This reaction involved TEMPO playing dual roles as both an oxidative dehydrogenation reagent and a ligand. An insight into the reaction mechanism was obtained by using several analytical determination methods.

Front Cover: Dialkyl Dicyanofumarates as Oxidizing Reagents for the Conversion of Thiols into Disulfides and Selenols into Diselenides (Eur. J. Org. Chem. 46/2017)

Front Cover: Dialkyl Dicyanofumarates as Oxidizing Reagents for the Conversion of Thiols into Disulfides and Selenols into Diselenides (Eur. J. Org. Chem. 46/2017)

Peroxidase-based oxidative polymerization of monolignols

Oxidative polymerization of the monolignols (sinapyl alcohol [SA] and coniferyl alcohol [CA]) has been performed using enzyme-based biocatalysts. The oxidation of SA, CA, or an SA/CA mixture has been carried out using peroxidase enzyme–assisted H 2 O 2 / t -BHP (oxidation reagent). The reaction provided radicals with high reactivity, in turn yielding a variety of polymeric structures. The efficiency of the oxidative polymerization system has been evaluated in terms of substrate conversion. Also, the polymeric products were characterized with the gel permeation chromatography technique (GPC). Accordingly, optimum experimental parameters have been set up (e.g. temperature, type of peroxidase enzyme, and oxidation reagent). Under optimum conditions, a maximum of 90% of the SA was transformed to polymeric products with MW = 3188 Da, Mn = 1115 Da, and PD = 2.8. L'oxy polymérisation de monolignols (SA, alcool de sinapyle, et CA, alcool de coniféryle) a été réalisée en utilisant un biocatalyseur enzymatique. Ainsi, SA, CA et un mélange de ces deux composés ont été oxydés par une peroxydase utilisant H 2 O 2 / t -BHP comme agent oxydant. La réaction fournit des produits radicalaires de haute réactivité, qui conduisent finalement à une structure polymérique. L‘efficacité de ce système d'oxy-polymérisation a été évaluée en terme de niveau de conversion. Les polymères produits sont caractérisés par analyse en CG. Une optimisation a été conduite en faisant varier des paramètres tels que la température, le type de peroxydase et la nature de l'agent oxydant. Dans les conditions optimales, un maximum de 90% de SA est transformé en polymère de MW = 3188 Da, Mn = 1115 Da et DP = 2.8.

Isolation and Characterization of Cellulose from Different Fruit and Vegetable Pomaces.

A new fractionation process was developed to achieve valorization of fruit and vegetable pomaces. The importance of the residues from fruits and vegetables is still growing; therefore; the study presents the novel route of a fractioning process for the conversion of agro-industrial biomasses, such as pomaces, into useful feedstocks with potential application in the fields of fuels, chemicals, and polymers. Hence, the biorefinery process is expected to convert them into various by-products offering a great diversity of low-cost materials. The final product of the process is the cellulose of the biofuel importance. The study presents the novel route of the fractioning process for the conversion of agro-industrial biomasses, such as pomaces, into useful feedstocks with a potential application in the fields of fuels, chemicals, and polymers. Therefore the aim of this paper was to present the novel route of the pomaces fraction and the characterization of residuals. Pomaces from apple, cucumber, carrot, and tomato were treated sequentially with water, acidic solution, alkali solution, and oxidative reagent in order to obtain fractions reach in sugars, pectic polysaccharides, hemicellulose, cellulose, and lignin. Pomaces were characterized by dry matter content, neutral detergent solubles, hemicellulose, cellulose, and lignin. Obtained fractions were characterized by the content of pectins expressed as galacturonic acid equivalent and hemicelluloses expressed as a xyloglucan equivalent. The last fraction and residue was cellulose characterized by crystallinity degree by X-ray diffractometer (XRD), microfibril diameter by atomic force microscope (AFM), and overall morphology by scanning electron microscope (SEM). The hemicelluloses content was similar in all pomaces. Moreover, all the materials were characterized by the high pectins level in extracts evaluated as galacturonic acid content. The lignins content compared with other plant biomasses was on a very low level. The cellulose fraction was the highest in cucumber pomace. The cellulose fraction was characterized by crystallinity degree, microfibril diameter, and overall morphology. Isolated cellulose had a very fine structure with relatively high crystalline index but small crystallites.

Application of Response Surface Methodology for Optimization of Treatment for an Aged Landfill Leachate Using Fenton's Oxidation Reagent

Abstract Landfill leachates can contain organic pollutants that may have an adverse impact on water bodies receiving the leachates unless some form of treatment reduces the pollutants to acceptable levels (often measured as biochemical oxygen demand and chemical oxygen demand [COD]). Age of the landfill can dictate treatment methods with younger landfill leachates that are often being treated using cheaper biotreatment processes and older landfills often requiring chemical and/or physical treatment due to the biorecalcitrance of the organics in these older landfill leachates. Fenton's reagent oxidation is a process with potential to significantly reduce COD from landfill leachates. Fenton's reagent oxidation reactions were carried out at room temperature (20 ± 5°C) and atmospheric pressure. Experiments were conducted by adding the necessary amount of FeSO4•7H2O and 30% (w/w) H2O2 to the leachate. Samples of reaction mixture were collected at specified times for COD analysis; 6 N sodium hydroxide solution ...

Pyrazine Radical Cations as a Catalyst for the Aerobic Oxidation of Amines

An efficient and green synthetic method for the preparation of N,N‐disubstituted tetramethylpyrazinium radical cations was developed, which does not require any solvent or strong alkylating agents. The investigation by UV/Vis and electron paramagnetic resonance (EPR) spectroscopy proved the stability of the prepared radical cation. Moreover, it was shown for the first time that the prepared N,N‐disubstituted tetramethylpyrazine can act as a powerful metal‐free catalyst for the selective oxidative homocoupling of amines to the corresponding imines under solvent‐free conditions. Furthermore, oxygen or even air can be employed as an efficient oxidative reagent.

A comparatively optimization of dosages of oxidation agents based on volatile solids and dry solids content in dewatering of sewage sludge

Organic content of sludge is a major factor influencing its dewaterability. Conditioning sewage sludge with oxidation reagents (Fenton's reagent or Fe2+/persulfate) can effectively improve sludge dewaterability. In traditional conditioning process of sewage sludge, the optimization of conditioner dosage were commonly based on volume of sludge (referred as mg/L) or mass of dry solid (DS) of sludge (referred as mg/g DS). However, inconsistency of the oxidation dose mode existed for different sewage sludge sources. In this study, sludge samples of different volatile solids (VS) contents were used to derive optimal dosages of Fenton's reagent and Fe2+/persulfate, using the response surface methodology (RSM). For the case of Fenton's reagent, the optimal dosages of Fe2+ and H2O2 were 107–110 mg/g VS and 86–88 mg/g VS, respectively. For Fe2+/persulfate, the optimal dosages of Fe2+ and persulfate were 49 mg/g VS and 269–271 mg/g VS, respectively. The optimal dosages of the oxidation reagents based on VS contents were proved to be consistent and effective for different sewage sludge with different organic matter contents from different wastewater treatment plants (WWTPs). In contrast, the optimal dosages of oxidation reagents, based on DS, fluctuated significantly for different sludge sources. Furthermore, sewage sludge dewaterability was significantly related to the degradation and the content of loosely bound extracellular polymeric substances (LB-EPS) in the organic matters of conditioned sludge (R2 > 0.9, p < 0.01). Thus, the improvement of sludge dewaterability could be related with the destruction of the VS in sludge with the conditioners of oxidant reagent. It indicated that optimization of oxidation reagent based on VS content is more plausible than that of based on DS content for different sewage sludge with different organic matter contents.

False-negative results in the immunoassay analysis of drugs of abuse: can adulterants be detected by sample check test?

Background The dilution or adulteration of urine is a serious problem in drugs of abuse testing. Tests to identify adulteration are currently available. This study investigated the ability of the CEDIA® sample check to detect adulteration. Methods Eight different drugs of abuse were added to a urine sample obtained from a healthy, drug-free subject: 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), 3,4-methylenedioxyamphetamine, benzoylecgonine, D-amphetamine sulphate, ethyl-D-glucuronide, morphine sulphate, oxazepam, (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol. Urine samples were diluted to yield three samples of drugs of abuse concentrations close to general cut-offs as used in methadone treatment centres, by health authorities for psychological tests and in traffic medicine. Aspirin, citric acid, CrO3, H2O2, soap, sodium metaborate, vitamin C were added in three, HCl and NaOH in one, and NaN3 in two concentrations. All samples were measured with commercially available immunological assays shortly after sample preparation and 24 h later. All samples were further analysed with the CEDIA® sample check reaction which may identify adulteration. Results Oxidizing reagents (H2O2 or CrO3) are most effective in interfering in the measurement of benzoylecgonine, EDDP, ethyl-D-glucuronide and morphine sulphate. The measurement of (-)-11-nor-9-carboxy-Δ9-tetrahydrocannabinol is affected by many adulterants. Adulteration with HCl and NaOH was identified with the sample check reaction. NaN3 generated false negative results for a number of drugs of abuse. Conclusions Urine samples with drugs of abuse concentrations above cut-offs can be successfully tampered with adulterants in a way which cannot be detected with the CEDIA® sample check assay.

Microwave‐assisted degradation of chitosan with hydrogen peroxide treatment using Box‐Behnken design for enhanced antibacterial activity

SummaryLow molecular mass (MM) chitosan with high degree of deacetylation (DDA) has excellent bioactivity including antioxidant, antibacterial and encapsulation properties. In this work, to reduce the MM of chitosan, microwave‐assisted heating treatment (MAHT) conditions were investigated using three factors at three levels Box‐Behnken design (BBD). Microwave heating (MH) time, H2O2 concentration and solid‐to‐liquid ratio significantly affected the DDA and MM of chitosan. The antibacterial activities of chitosan before and after degradation were investigated based on minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The results showed that a second‐order polynomial equation fitted the observed values using multiple regression analysis and had a high coefficient of determination (R2 = 0.9591 and 0.9161 for the DDA and MM of chitosan, respectively). An optimisation study was performed using Derringer's desirability function methodology, and the optimal conditions were 80‐s MH time, 1.5% H2O2 concentration and 1:40 solid‐to‐liquid ratio. The MIC and MBC of chitosan before and after degradation against Escherichia coli and Salmonella typhimurium were 0.031 and 0.063 mg mL−1, and 0.25 and 0.125 mg mL−1, respectively. The optimised DDA and MM of chitosan were 90.58 ± 2.04% and 124.25 ± 14.36 kDa, respectively, which significantly reduces the use of oxidant reagent.

Dialkyl Dicyanofumarates as Oxidizing Reagents for the Conversion of Thiols into Disulfides and Selenols into Diselenides

Aliphatic and aromatic thiols react smoothly with dialkyl dicyanofumarates in CH2Cl2 at room temperature to give the corresponding disulfides in excellent yields. Aliphatic 1,2‐, 1,3‐, and 1,4‐dithiols afford cyclic disulfides. Analogous reaction courses were observed for selenols, and the required diselenides also formed in nearly quantitative yields. In all of the reactions, dialkyl dicyanosuccinates formed as 1:1 mixtures of diastereoisomers as the only other product. Cysteamine (2‐mercaptoethylamine) behaved differently; the Michael addition of the primary amine group led to the complete consumption of the dicyanofumarate, and the formation of the disulfide containing an enamine moiety occurred without the formation of dicyanosuccinate.

Hydrogen Peroxide‐Induced Oxidative Dimerization of Wittig Reagents: Improving the Selectivity, Yield and Expanding to the Aryl System

AbstractUnder the protection of nitrogen, the use of THF as best solvent can increase the yield or stereoselectivity of the H2O2 induced oxidation of Wittig reagents to give the corresponding dimerization products (trans‐alkenes) as the major or only product in better to good yields up to 98 %. This reaction can be expanded to the aryl system in the yield up to 94 % for homo‐coupled dimers or 58 % for cross coupled dimers. This result will expand the synthetic application scope of Wittig reagents and H2O2.

Structure and thermoelectric properties of Cs-Bi-Te alloys fabricated by different routes of reduction of oxide reagents

Cesium-bismuth-telluride polycrystalline materials were fabricated using a cost-effective method based on a reduction of oxide reagents, leading to a production of a material with good thermoelectric properties. Several samples with various initial stoichiometry were prepared by melting of oxide powders at 1050 °C, quenching, milling to powders and then reducing in pure hydrogen at 400 °C. Another concept was to obtain the CsBi4Te6 material without a melting stage. Composition of the samples was analyzed by the XRD and EDX methods. The sample with 96% of CsBi4Te6 phase was obtained in a way of reduction of oxide reagents. Thermoelectric properties of fabricated samples were also investigated.

Versatile Dual Photoresponsive System for Precise Control of Chemical Reactions.

A versatile method for photoregulation of chemical reactions was developed through a combination of near-infrared (NIR) and ultraviolet (UV) light sensitive materials. This regulatory effect was achieved through photoresponsive modulation of reaction temperature and pH values, two prominent factors influencing reaction kinetics. Photothermal nanomaterial graphene oxide (GO) and photobase reagent malachite green carbinol base (MGCB) were selected for temperature and pH regulation, respectively. Using nanocatalyst- and enzyme-mediated chemical reactions as model systems, we demonstrated the feasibility and high efficiency of this method. In addition, a photoresponsive, multifunctional "Band-aid"-like hydrogel platform was presented for programmable wound healing. Overall, this simple, efficient, and reversible system was found to be effective for controlling a wide variety of chemical reactions. Our work may provide a method for remote and sustainable control over chemical reactions for industrial and biomedical applications.

A new oxidative reagent synthesis and its applications: Tetrakis-(2,4,6-trimethylpyridine)silver(I) dichromate (T-TMPSDC)

Tetrakis -(2,4,6-trimethylpyridine)silver(I) dichromate (T-TMPSDC) was easily synthesized by addition of 2,4,6-trimethylpyridine to an aqueous precipitation of silver dichromate and characterized thoroughly, using spectroscopic and others analytical methods such as FT-IR, 1 H NMR, 13 C NMR, DTA, SEM-EDS and XRD. When T-TMPSDC was used as an oxidative reagent, it showed selectivity in the oxidation of primary, secondary and benzylic alcohols to their corresponding carbonyl compounds in presence of benzylic carbons and arenes such as tetraline, anthracene and phenanthrene.

Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials

AbstractThe extraction of gold from ores and electronic waste is an important topic worldwide, as this precious metal has immense value in a variety of fields. However, serious environmental pollution and high energy consumption due to the use of toxic oxidation reagents and harsh reaction conditions is a well‐known problem in the gold industry. Herein, we report a new chemical method based on the combined use of N‐bromosuccinimide (NBS) and pyridine (Py), which has a greatly decreased environmental impact and reagent cost, as well as mild reaction requirements. This method can directly leach Au0 from gold ore and electronic waste to form AuIII in water. The process is achieved in a yield of approximately 90 % at room temperature and a nearly neutral pH. The minimum dose of NBS/Py is as low as 10 mm, which exhibits low toxicity towards mammalian cells and animals as well as aquatic creatures. The high leaching selectivity of Au over other metals during gold leaching is demonstrated, showing that this method has great potential for practical industrial application towards the sustainable refining of gold from ores and electronic waste.