Reagent For Oxidation Research Articles

ChemInform Abstract: o‐Iodoxy Benzoic Acid—Mediated Synthesis of 3,5‐Diarylisoxazoles and Isoxazole‐3‐carboxylic Acids.

Abstractvia oxidative cyclization of α,β‐unsaturated ketoximes (I) or (III), resp., using IBX as efficient, environmentally friendly and nontoxic oxidation reagent

Lewis acid catalysis and Green oxidations: sequential tandem oxidation processes induced by Mn-hyperaccumulating plants.

Among the phytotechnologies used for the reclamation of degraded mining sites, phytoextraction aims to diminish the concentration of polluting elements in contaminated soils. However, the biomass resulting from the phytoextraction processes (highly enriched in polluting elements) is too often considered as a problematic waste. The manganese-enriched biomass derived from native Mn-hyperaccumulating plants of New Caledonia was presented here as a valuable source of metallic elements of high interest in chemical catalysis. The preparation of the catalyst Eco-Mn1 and reagent Eco-Mn2 derived from Grevillea exul exul and Grevillea exul rubiginosa was investigated. Their unusual polymetallic compositions allowed to explore new reactivity of low oxidative state of manganese-Mn(II) for Eco-Mn1 and Mn(IV) for Eco-Mn2. Eco-Mn1 was used as a Lewis acid to catalyze the acetalization/elimination of aldehydes into enol ethers with high yields; a new green and stereoselective synthesis of (-)-isopulegol via the carbonyl-ene cyclization of (+)-citronellal was also performed with Eco-Mn1. Eco-Mn2 was used as a mild oxidative reagent and controlled the oxidation of aliphatic alcohols into aldehydes with quantitative yields. Oxidative cleavage was interestingly noticed when Eco-Mn2 was used in the presence of a polyol. Eco-Mn2 allowed direct oxidative iodination of ketones without using iodine, which is strongly discouraged by new environmental legislations. Finally, the combination of the properties in the Eco-Mn catalysts and reagents gave them an unprecedented potential to perform sequential tandem oxidation processes through new green syntheses of p-cymene from (-)-isopulegol and (+)-citronellal; and a new green synthesis of functionalized pyridines by in situ oxidation of 1,4-dihydropyridines.

UV/persulfate and UV/hydrogen peroxide processes for the treatment of salicylic acid: effect of operating parameters, kinetic, and energy consumption

Two advanced oxidation processes (AOPs), based on UV light irradiation with potassium persulfate (UV/KPS) and with hydrogen peroxide (UV/H2O2), were employed for the treatment of salicylic acid (SA) in aqueous media. The influence of operating parameters, initial pH and concentration of the oxidant reagents, was investigated. Under the optimum conditions of pH 6 and [KPS] = 1,000 mg/L for UV/KPS and pH 4 and [H2O2] = 140 mg/L for UV/H2O2, about 94 and 98% SA degradations were achieved after 60 min treatments. Total organic carbon removal was also obtained as 80% and 87%, respectively, after 150 min. Rate of SA degradation in these processes obeys pseudo-first-order kinetic. For UV/KPS process, the role of active radicals was studied using ethanol and tert-butyl alcohol radical scavengers, indicating the contribution of hydroxyl and sulfate radicals in the degradation of about 56% and 44%, respectively. The electrical energy consumption, for nearly complete degradation of SA, was evaluated and the preference was shown in comparison with previous works.

Direct conversion of alcohols to α-chloro aldehydes and α-chloro ketones.

Direct conversion of primary and secondary alcohols into the corresponding α-chloro aldehydes and α-chloro ketones using trichloroisocyanuric acid, serving both as stoichiometric oxidant and α-halogenating reagent, is reported. For primary alcohols, TEMPO has to be added as an oxidation catalyst, and for the transformation of secondary alcohols (TEMPO-free protocol), MeOH as an additive is essential to promote chlorination of the intermediary ketones.

ChemInform Abstract: Continuous‐Flow Synthesis of Functionalized Phenols by Aerobic Oxidation of Grignard Reagents.

Phenols are important compounds in chemical industry. An economical and green approach to phenol preparation by the direct oxidation of aryl Grignard reagents using compressed air in continuous gas-liquid segmented flow systems is described. The process tolerates a broad range of functional groups, including oxidation-sensitive functionalities such as alkenes, amines, and thioethers. By integrating a benzyne-mediated in-line generation of arylmagnesium intermediates with the aerobic oxidation, a facile three-step, one-flow process, capable of preparing 2-functionalized phenols in a modular fashion, is established.

Ester Hydrolysis of Polysorbate 80 in mAb Drug Product: Evidence in Support of the Hypothesized Risk After the Observation of Visible Particulate in mAb Formulations

An observation of visible particulate matter was made during formulation development of a mAb and investigations initiated to understand the colloidal instability of the formulation. It was observed that there was a loss of polysorbate in the IgG formulation and concurrent hydrolysis of polysorbate 80 (PS80) into fatty acid, polyethylene glycol (PEG), and pegylated sorbitan in the presence of mAb A. This observation was confirmed with two other mAb development programs (mAb B and mAb C) that used PS80 and formed particulate, but was absent in any placebo sample tested. Comparative analysis to acid, base and esterase hydrolysis, and exposure to the oxidation reagents Iron(II) and tert-Butyl hydroperoxide demonstrates that the observed reaction is reproduced by a biologic (enzymatic) mechanism. Monooleates of PS80, including the sorbitan and PEG oleates, are hydrolyzed first, showing a slower reaction with higher-order oleates. This leads to a change in the composition of the formulation over time where PS85 becomes the predominant component of the original surfactant remaining in solution. Data suggest that there is a lipid-specific mechanism rather than a general biologic hydrolysis mechanism that hydrolyzes oleate esters of PS80 increasing the risk that colloidal IgG particles will form in mAb drug product.

Efficient and robust superparamagnetic copper ferrite nanoparticle-catalyzed sequential methylation and C–H activation: aldehyde-free propargylamine synthesis

We have described a method for oxidative cross-coupling reactions between N-alkyl anilines and terminal alkynes forming N-aryl-N-methylpropargylamines. Superparamagnetic CuFe2O4 nanoparticles were employed as efficient and robust catalyst. The optimum conditions involved the use of tert-butyl hydroperoxide (TBHP) as oxidant and methylating reagent in dimethylacetamide (DMA) solvent at 140 °C. The two-step reaction, methylation and C–C cross-coupling, proceeds efficiently and has high selectivity, and good conversions were achieved in short reaction times. Preliminary mechanistic investigation was conducted. The CuFe2O4 nanoparticles could be facilely separated from the reaction mixture by magnetic decantation and could be reused several times with only a slight decrease in catalytic activity.

ChemInform Abstract: Gold‐Catalyzed Alkynylation: Acetylene‐Transfer Instead of Functionalization

AbstractReview: 89 refs.

Highly selective acetoxylation of sulfonamides via using phenyliodine(III) diacetate

A highly efficient acetoxylation reaction of N-aryl-arylsulfonamides has been developed, presumably proceeding via the selective functionalization of N-aryl C–H bonds. A stoichiometric amount of PhI(OAc)2 was generally employed as the oxidation reagent, and various para-acetoxylated sulfonamide derivatives had been generated in excellent yields. This chemistry endowed an economic synthesis of valuable acetoxylated sulfonamides through direct C–O bond formation processes.

S4-1 CO-CBS system for regulating tenuous balance between nadph and persulfides in cancer

Heme oxygenase-1/CO protects cancer cells from oxidative stress, but the gas-responsive signaling mechanisms remain unknown. Here we show using metabolomics that CO-sensitive methylation of PFKFB3, an enzyme producing fructose 2,6-bisphosphate (F-2,6-BP), serves as a switch to activate phosphofructokinase-1, a rate-limiting glycolytic enzyme. Stress-induced CO inhibits cystathionine beta-synthase (CBS), and thereby modulate methylation of many proteins including PFKFB3, an switching enzyme determining the balance of glucose metabolism between glycolysis and pentose phosphate pathway. In several different cancer cell lines derived from human, PFKFB3 is asymmetrically di-methylated at R131 and R134 through modification by protein arginine methyltransferase-1. HO-1 induction or CO results in reduced methylation of PFKFB3 in varied cancer cells to suppress F-2,6-BP, shifting glucose utilization from glycolysis toward pentose phosphate pathway. Loss of PFKFB3 methylation depends on the inhibitory effects of CO on heme-containing cystathionine beta-synthase (CBS). CBS modulates remethylation metabolism, and increases NADPH to supply reduced glutathione, protecting cells from oxidative stress and anti-cancer reagents. Once the methylation of PFKFB3 is reduced, the protein undergoes polyubiquitination and is degraded in proteasomes. CBS knockdown in HCT116 cells stimulates cancer cell proliferation, so far as seen in a hepatic metastatic model of the cancer xenografts. Under the given condition, tumors increased GSH levels but with decreasing glutathione S-sulfonate, a product derived from GSS − in vivo. These results suggest that the CO/CBS determines the balance between NADPH and endogenous persulfides, and CBS-sensitive PFKFB3 methylation 1 determines directional glucose utilization to ensure resistance against oxidative stress for cancer cell survival.

Thermodynamic Simulation of the Oxidation Processes of Ag<sub>2</sub>Se by NaNO<sub>2</sub>

The thermodynamic simulation of the oxidation processes of silver selenide by reagents such as NaNO2, NaNO3 and NaOH during their heat treatment has been conducted. Gibbs energy of silver selenide oxidation reactions has been estimated. It is shown as a reagent–oxidant of silver selenide it is rationally to use a mixture of sodium nitrite and sodium hydroxide. Oxidation of silver selenide during heat treatment together with sodium nitrite and sodium hydroxide is accompanied by the formation of soluble compounds such as Na2SeO3 and Na2SeO4, silver being passed in the metallic state. Separation coefficients characterizing oxidation efficiency and the level of selenium transfer in soluble compounds were estimated. Using the data the separation method of materials containing selenides by means of their sintering with sodium-containing reagents is proposed. The method is based on the transfer of selenium in the water-soluble compounds followed by leaching, precious metals being the elemental state. The products obtained are suitable for the production of selenium and precious metals by traditional technologies.

O-Iodoxy Benzoic Acid–Mediated Synthesis of 3,5-Diarylisoxazoles and Isoxazole-3-carboxylic Acids

A new, convenient, ecofriendly synthesis of 3,5-diarylisoxazoles is reported from α,β-unsaturated ketoximes. Similarly, a novel synthesis of isoxazole carboxylic acids is also reported. Both the methods use efficient, environmentally friendly, and nontoxic iodoxybenzoic acid (IBX) as an oxidative cyclizing reagent. Easy procedure, environmentally benign reaction conditions, and nontoxicity are advantages to the methodology.

Development of Binderless Fiberboards from Steam-exploded and Oxidized Oil Palm Wastes

Binderless fiberboards were made from oil palm (Elaeis guineensis) empty fruit bunches with two treatments: steam explosion and Fenton reagent oxidation. Fiberboards were prepared with a targeted density of 1.20 g/cm3 and a thickness of 4 mm. A factorial experimental design 22 with two center repetitions and one repetition was applied for each treatment. The oil palm waste was oxidized with Fenton reagent using a H2O2/Fe2+ ratio of 2%/0.2% to 4%/0.4% and a pressing temperature of 170 to 190 °C. Steam explosion was carried out at a severity factor of 3.5 to 4.0 at the same pressing temperature. Both treatments were examined under two major response variables: mechanical properties (modulus of rupture, MOR, and modulus of elasticity, MOE) and physical properties (thickness swelling, TS, and water absorption, WA). Steam-exploded samples developed better physico-mechanical properties than those that underwent Fenton reagent oxidation. The best results were obtained from fiberboards treated with the highest steam explosion design conditions (severity 4 and pressing temperature 190 °C) to give optimum values of MOE 3100.09 MPa, MOR 28.49 MPa, TS 11.80%, and WA 22.74%. Binderless fiberboards made from steam explosion-treated pulp satisfied favorably well the Colombian Standard NTC 2261.

Lignite oxidative desulphurization

AbstractThe process of lignite desulphurization via its treatment by an oxidant (air or air–steam mixture) has been studied. The research objective was useful determination of steam application in oxidative lignite desulphurization. It has been proved that the water steam should be included in the oxidant composition to increase the hydrogen sulphide and combustible constituent content in the gases obtained during the processes under research. The impact of factors which affect the reactions between solid (in our case – lignite) and gaseous reagent (oxidant, i.e. air and or air–steam mixture) upon the research process has been investigated, if these reactions occur in the kinetic area. Such factors are linear rate of oxidant movement and coal grain size. The values of oxidant movement linear rate and coal grain size, which the reaction transfer from pyrite sulphur and organic content of lignite from diffusion into kinetic area occurs by, have been determined. Under these “transfer” conditions, the values of coefficients of oxidant mass transfer (β, m/s) as well as Sherwood criteria and boiling layer differences have been calculated.

Continuous‐Flow Synthesis of Functionalized Phenols by Aerobic Oxidation of Grignard Reagents

AbstractPhenols are important compounds in chemical industry. An economical and green approach to phenol preparation by the direct oxidation of aryl Grignard reagents using compressed air in continuous gas‐liquid segmented flow systems is described. The process tolerates a broad range of functional groups, including oxidation‐sensitive functionalities such as alkenes, amines, and thioethers. By integrating a benzyne‐mediated in‐line generation of arylmagnesium intermediates with the aerobic oxidation, a facile three‐step, one‐flow process, capable of preparing 2‐functionalized phenols in a modular fashion, is established.

Continuous‐Flow Synthesis of Functionalized Phenols by Aerobic Oxidation of Grignard Reagents

Phenols are important compounds in chemical industry. An economical and green approach to phenol preparation by the direct oxidation of aryl Grignard reagents using compressed air in continuous gas-liquid segmented flow systems is described. The process tolerates a broad range of functional groups, including oxidation-sensitive functionalities such as alkenes, amines, and thioethers. By integrating a benzyne-mediated in-line generation of arylmagnesium intermediates with the aerobic oxidation, a facile three-step, one-flow process, capable of preparing 2-functionalized phenols in a modular fashion, is established.

Bromide-bromate Couple of Varying Ratios for Bromination, Vicinal Functionalisation and Oxidation in a Clean Manner

The review highlights applications of bromide-bromate couple in organic synthesis. The couple having 5:1 mole ratio of bromide to bromate is useful for preparation of dibromo derivatives from alkenes/alkynes. The 2:1 couple affects substitution with high bromine atom efficiency. Vicinal functionalization of olefins has also been studied. The 1:8 bromide-bromate couple has proved promising in several oxidation reactions, the performance exceeding that of bromate alone. This reagent was also the most effective for deiodination of styrene-based iodohydrins with concomitant rearrangement by a novel pathway. In all the cases the reagents were activated through in situ acidification. The 5:1 reagent is obtained as intermediate during liquid bromine manufacture and the other reagents were prepared from it using ClO-. Liquid bromine could be avoided in the product life cycle. Keywords: Bromide-bromate couples, direct preparation from bromine intermediate, In situ activation, reagents for green bromination and oxidation, regeneration and reuse.

Texture etching of monocrystalline silicon surface with sodium hypochlorite

Silicon etching in alkaline solutions has been employed for many years, in the fabrication of solar cells. Surface texturisation of crystalline silicon was performed by using different etching solutions. Recently, a strong oxidising reagent NaOCl has been used successfully by several authors to texture the silicon surface. In this work, the effect of the etching parameters such as solution composition on the silicon surface morphology is studied. The surface of etched samples was analysed by scanning electron microscopy (SEM), spectrophotometry and secondary ion mass spectroscopy (SIMS). The results clearly show that the presence of ethanol in the solution leads to the formation of pyramids, while its absence induces the formation of nanostructures (nanowire or nanoneedle).

Screening of elemental impurities in commercial detonation nanodiamond using sector field inductively coupled plasma-mass spectrometry

The quantitation of 55 elemental impurities in 15 commercial samples of detonation nanodiamond (DND), micron-sized diamond of high pressure/high temperature synthesis and detonation synthesis soot (DS) was achieved using a direct sector field ICP-MS analytical method. A set of 23 elements contributing more than 99.8 mass % of all impurities was selected and used as markers for the evaluation of DND purity. Obtained data were evaluated to identify important information on possible sources of nanodiamond contamination during purification, disaggregation, solubilisation or stabilisation of suspensions. Distinctive groups of elements (including Cr, Mn and S; Mo, W, V and Ti; Na, B and Si; Ca and Mg) occurring at elevated levels in DND can be readily visualised using radar plots, and can be related to the detonation synthesis (construction materials of explosion chamber, admixture in coolant, detonator type) and/or purification processes (type of oxidation process and reagents). The contaminant profile for each respective DND can be also considered as a fingerprint, characteristic for every producer and technology used. Results obtained also highlight how DND can be considered as effective collectors of various inorganic impurities from chemical reagents, glassware, sonotrode and other materials used during processing, including disaggregation and stabilisation of suspensions.

Synthesis of Microwires of Polypyrrole via Chemical Polymerization using Track Etch Membrane as Template

Low dimensional structures of conducting polymers, particularly polypyrrole, have attracted a great attention of researchers and engineers in recent years because of their diverse potential application on account of their unique properties of large aspect ratio, good electrical conductivity, environmental stability and biocompatibility. The present work describes synthesis of polypyrolle microwires by template assisted chemical polymerization at room temperature using FeCl3 as an oxidant. In this technique, the track etch membrane used as a template was fitted between two chambers in a chemical cell in such a way that the template acts as a separating wall between the chambers. One chamber was filled with an aqueous monomer pyrrole solution and other was filled with oxidant reagent of ferric chloride. Chemical polymerization takes place within the pores of the template as the monomer and the oxidant reagent diffuse towards each other, react to yield the conductive polymer which grows as microstructure in the shape of pores of host template. Synthesized samples have been characterized by Scanning Electron Microscopy (SEM), which reveals that the morphology of the microwires matches with the morphology of pores as mould in host template. Diameter, orientation and direction of growth of microwires were almost uniform because of the confined growth of microwires in the ordered and symmetric pores of TEM template. Conductivity of polypyrrole microwires was estimated equal 20.152 S/m form current-voltage characteristics measured using a two-probe-method.