Reagent For Oxidation Research Articles

On mechanism of reduction on DME of some compounds with local anesthetic activity N-oxides containing tertiary amine

It has been shown for the first time the obtaining of N-oxides of dymedrol (DMD) and bupivacaine (BVK). Bupivacaine is a local anesthetic of amide group. Dymedrol (diphenhydramine hydrochloride) is an antihistamine that reduces the effects of natural chemical histamine in the body. The N-oxides of DMD and BVK are formed during chemical oxidation with potassium peroxymonosulfate (KPMS). The first step was investigation of the optimal conditions for oxidation reaction to reach the maximum yield of final products (N-oxides). The investigated conditions were pH, time of oxidation and ratio of reagents. The needed time for oxidation of DMD and BVK is 10 min. At least two-fold excess of KPMS must be in the solution in recount to analyte concentration, but not higher than 10 -4 M. The maximum concentration of BVK and DMD N-oxides was obtained in weakly basic medium (pH 8.5–9.3). The second step was optimization of conditions for polarographic reduction of BVK and DMD N-oxides on the dropping mercury electrode (DME). The best medium for electrochemical reduction was the medium of phosphate buffer solution with pH in the range 5–6. On polarogramms it was observed only one irreversible peak in full pH range studied. The rate of electrochemical reaction is diffusion-controlled with weak adsorption of BVK, other local anesthetics (LA) (lidocaine, mepivacaine and trimecaine) and DMD N-oxides on DME surface confirmed by studying of effect of scan rates on polarogramms characteristics. The reduction potentials of peak linearly depend on solution pH. Thus, the electrochemical reduction of LA and DMD N-oxides includes protonation reaction stage. Based on literature survey and our calculations it was suggested that reduction mechanism of BVK and DMD N-oxides consist in monoelectron transfer resulting in anion-radical formation proceeding one proton adjunction. Keywords : polarography, N-oxides, local anesthetics, dymedrol, bupivacaine.

Ruthenium-catalyzed ortho-selective CAr-H amination of heteroaryl arenes with di-tert-butyldiaziridinone.

Application of an oxidative amination reagent (di-tert-butyldiaziridinone) to the Ru3(CO)12-catalyzed ortho-selective CAr-H amination reaction is described. This strategy shows good functional group compatibility with various phenyl-substituted N-heterocycles, including biologically active substrates, thus providing synthetic potential for this methodology. Mechanistic studies showed that the reaction process involves an octahedral ruthenium species, and the carbon monoxide ligand plays a crucial role in the C-H activation.

Asparagine as a Green Organocatalyst for the Synthesis of 2-Aminothiazoles

In this research, an efficient method for the one-pot synthesis of 2-aminothiazoles via the reaction of thiourea with methylcarbonyls in the presence of iodine as an oxidant reagent has been developed using asparagine as a green organocatalyst at 80 °C in DMSO solvent. Advantages of this efficient method include greener and cleaner conditions, easy isolation of products, higher purity and excellent yield of products, and convenient manipulation.

Palladium-catalyzed microwave-assisted Hirao reaction utilizing the excess of the diarylphosphine oxide reagent as the P-ligand; a study on the activity and formation of the “PdP2” catalyst

Abstract The microwave-assisted Hirao reaction of bromobenzene and diarylphosphine oxides was performed at 120 °C using triethylamine as the base, and 5% of palladium acetate as the catalyst in ethanol. 5% Excess of the >P(O)H reagent served as the reducing agent, while another 10% as the preligand (in the >POH tautomeric form). It was found that the P–C coupling reaction was significantly faster with (2-MeC6H4)2P(O)H (A) and (3,5-diMeC6H3)2P(O)H (B), than with Ph2P(O)H (C) and (4-MeC6H4)2P(O)H (D). Moreover, species A and B could be applied as selective P-ligands in the reaction of bromobenzene with C or D. Dependence of the effectiveness of “PdP2” catalysts with diarylphosphine oxide preligands on the methyl substituents followed a reversed order as the reactivity of the diarylphosphine oxide species in the P–C coupling itself. Formation of the “PdP2” catalyst from palladium acetate and diarylphosphine oxide has never been studied, but now it was evaluated by us at the B3LYP level of theory applying 6-31G(d,p) for C,H,P,O and SDD/MW28 for Pd including the explicit-implicit solvent model. The novel mechanism requiring three equivalents of the >P(O)H species for each of the palladium acetate molecule was in agreement with the preparative experiments. The ligation of palladium(0) with different P(III) species comprising the >POH form of the >P(O)H reagent was also studied, and the critical role of the steric hindrance on the ligation, and hence on the activity of the “PdP2” catalyst was substantiated. Last but not least, the influence of the Me substituents in the aromatic ring of the P-reagents on the energetics of the elemental steps of the Hirao reaction itself was also evaluated.

Silica-supported ceric ammonium nitrate (CAN): a simple, mild and solid-supported reagent for quickest oxidative aromatization of Hantzsch 1,4-dihydropyridines

An efficient and environmentally benign methodology for the oxidative aromatization of 1,4-dihydropyridines to their corresponding pyridine derivatives is developed. The oxidative aromatization of 1,4-dihydropyridines was explored using silica-supported ceric ammonium nitrate as catalyst in CH3CN with or without sonication at room temperature. This supported catalyst acts as a more efficient oxidising reagent and offers several advantages over other reported reagents in terms of reaction time and yields. The supported reagent is found to be more efficient and selective when compared with its unsupported form. The Belousov–Zhabotinskii reaction was not observed in present reaction. The dealkylation observed in case of 4-n-alkyl/n-alkenyl with other oxidising agents is also not observed in the present case.

Oxidative modification of graphite felts for efficient H2O2 electrogeneration: Enhancement mechanism and long-term stability

Hydrogen peroxide (H2O2) is considered to be an environmentally friendly chemical and the production methods of H2O2 based on the oxygen reduction reaction (ORR) in the electrochemical system can achieve in-situ generation. The yield of H2O2 is highly dependent on cathode materials. However, the commercial graphite felts (GFs) have a low electrocatalytic activity, which greatly limits its wide-spread application. Here, three kinds of methods (H2O2 oxidation, Fenton reagent oxidation and electrochemical oxidation) were used to modify GFs as the cathode for electrochemical H2O2 production. Characterized by SEM, contact angle and XPS, the morphology and surface physicochemical properties after modification were considerably changed. After modification, the surface of GFs was etched, and some oxygen-containing functional groups (OGs) especially COOH appeared on the surface, leading to the improvement of the surface hydrophilic and the electrocatalytic activity for ORR. The H2O2 production of three GFs at 90min were 18.67mg/L, 32.13mg/L and 37.47mg/L, respectively, compared to only 3.24mg/L by the original GFs. Additionally, the long-term stability of modified GFs were studied and the mechanism of the decreased stability was proposed. After 10 consecutive cycles, the H2O2 production of three modified GFs decreased by 42.29%, 61.24% and 58.19%, respectively. SEM, contact angle and XPS showed that the surface of the GFs was etched more, and the COOH content of all three materials significant decreased.

A Vacuum-Free Method for Producing Cubic Titanium Carbide in the Plasma of Low-Voltage Direct-Current Arc Discharge

The results of a study on the production of cubic titanium carbide in direct-current arc discharge plasma initiated in open air are presented. A feature of the method is its implementation without the use of gas or liquid protective media preventing the oxidation of products and initial reagents with air oxygen. According to the X-ray diffraction data, graphite gC, hexagonal titanium α-Ti, and cubic titanium carbide TiC are identified in the composition of the powder product. The TiC particles are represented by objects with a regular characteristic cut and sizes from units to tens of micrometers.

Electrochemical synthesis of polypyrrole in powder form

Novel approach to synthesis of conjugated oligomers/polymers is proposed. This approach combines all advantages of electrochemical methods: variation of the oxidation potential in wide range with high precision, direct control of the process rate and product yield, variation of both the doping anion/cation nature and the composition of polymerization medium, absence of chemical oxidative reagents in reaction mixture. Contrary to the conventional use of this synthetic method, it has been exploited in our study for generation of polymeric products outside the electrode surface. This goal has been implemented via oxidation of the monomer at porous electrode with simultaneous pumping of the polymerization medium (monomer in background electrolyte solution) through porous electrode with a certain rate. It leads to electrochemical generation of active intermediates (cation radicals) at the electrode surface with their recombination and subsequent accumulation of the products not only as film on the electrode surface but also as a colloid in solution outside the porous medium. Since this reaction path toward bulk solution products should evidently be favored by slow steps in the course of the polymer formation, this approach has been tested for pyrrole oxidation (both in its pure monomer solution and in the presence of the bromide redox mediator) since this monomer is known of its high rate of polymer chain formation.

Unsubstituted metallophthalocyanine catalysts for the removal of endocrine disrupting compounds using H2O2 as oxidant

Advanced oxidation processes have become increasingly important to treat non-biodegradable compounds entering environmental waters. In recent decades, water-soluble metallophthalocyanines have been shown to catalyse H2O2-containing oxidation reactions through the production of unique reactive species, nucleophilic metal-peroxo complexes. Few reports in the literature have examined water insoluble metallophthalocyanines (MPc). The oxidative catalytic activity of water insoluble manganese- and iron-phthalocyanine (MnPc, FePc) at pH7 has been shown through the decolourisation of methylene blue and removal of bisphenol A. These studies expand on this previous study, exploring the catalytic activity of a range of metallophthalocyanines catalysts under both acidic and neutral conditions. FePc, while only active under neutral conditions, was the best performing catalyst. This activity was significantly improved upon by the addition of acetonitrile as a co-solvent, as well as increasing the ratio of H2O2 to catalyst. MnPc was catalytically active at both pH3 and 7. FePc and MnPc catalysts showed the ability to remove bisphenol A in the presence of dam water. Reaction rates were reduced for bisphenol A removal with FePc as a catalyst but were unchanged in the presence of MnPc. The removal of 17β-estradiol, estrone, and coumestrol was successfully demonstrated, with greater than 96% removal of all tested EDC's achieved. This is the first reported study showing the removal of the phytoestrogen, coumestrol. Even though considerably lower concentrations of costly catalysts and oxidation reagents were used in our work, the removal extent of EDC's by the MPc-catalysed oxidation reactions achieved here compares favourably with literature.

TITRIMETRIC ASSAY OF SOME ANTIHISTAMINE DRUGS WITH PYRIDINIUM FLUORO CHROMATE (PFC) REAGENT

In the present paper, simple, convenient accurate, precise and cost effective titrimetric (Visual volumetric) method has been reported for the estimation of some antihistamine drugs e.g. Cyproheptadine hydrochloride (CPH), Fexofenadine hydrochloride (FFH), Promethazine hydrochloride (PMH) and Pheniramine maleate (PM) in pure form and in their pharmaceutical preparations such as Ciplactin (Tab), Allegra (Tab), Phenergan (Tab and Inj) and Avil (Tab and Inj) with Pyridinium fluoro chromate (PFC) reagent. The principle of this method is based on the fact, that each pharmaceutical drug consists of certain organic functional group which on oxidation by a known excess of potassium iodate in sulphuric acid medium followed by iodometric titration in presence of reagent Pyridinium fluoro chromate (PFC) establishes stoichiometric relationship between drug molecule and an oxidising reagent Pyridinium fluoro chromate (PFC).Different results obtained for each drug during experiment, has been validated by different statistical parameters such as percentage error, standard deviation (SD) and coefficient of variation (CV).Results obtained from these statistical parameters proves the accuracy and precision of adopted method.

A Two-Step Oxidative Cleavage of 1,2-Diol Fatty Esters into Acids or Nitriles by a Dehydrogenation-Oxidative Cleavage Sequence.

Dehydrogenative oxidation of vicinal alcohols catalyzed by a commercially 64 wt.% Ni/SiO2 catalyst leads to the formation of α-hydroxyketone. This first step was developed without additional solvent according to two protocols: "under vacuum" or "with an olefin scavenger". The synthesis of ketols was carried out with good conversions and selectivities. The recyclability of the supported nickel was also studied. Acyloin was then cleaved with oxidative reagent "formic acid/hydrogen peroxide", which is cheap and can be used on a large scale for industrial oxidation processes. The global yield of this sequential system was up to 80 % to pelargonic acid and azelaic acid monomethyl ester without intermediate purification. By treating the acyloin intermediate with hydroxylamine, nitriles were obtained with a good selectivity.

SYNTHESIS AND CYTOTOXICITY OF POLYHYDROXYLATED CHOLESTEROL DERIVATIVES

Eight polyhydroxylated cholesterol derivatives (1-8) were prepared from cholesterol, using oxidative reagents as SeO2, OsO4/NMO, HCOOH/H2O2 and BH3/ H2O2. Their structures were elucidated by using physical methods including NMR 1D and 2D. These compounds were evaluated against two cancer cell lines (Hep-G2, T98). Compounds 2, 4 and 8 inhibits human hepatocellular carcinoma cell line (Hep-G2) with IC50 4.69, 4.98 and 2.89 µg/mL, respectively. In addition, compound 8 exhibited strong cytotoxicity against T98 cell line (glioblastoma) with IC50 = 2.28 μM.

Synthesis and Characterizations of (CoxMg(2-x))SiO₄ Forsterite Ceramic Pigments from Mirror Waste.

Ceramic pigments have been widely used in a variety of industries because of their excellent properties, such as high thermal stability, low-cost productions, and simple manufacturing processes. Re-use of mirror waste, which consists of silicon dioxide greater than 70%, is a method that can reduce raw materials cost. In this work, ceramic pigment with forsterite structure, Mg2SiO4, was synthesized via conventional solid state reaction by using mirror waste as a precursor. Solid solutions of Co-doped forsterite pigment, CoxMg(2−x)SiO4 where x = 0.02–1.6, were calcined at 1000 °C for 2 h. The calcined powders were characterized by X-ray diffraction technique (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectrophotometer, and color measurement (CIEL*a*b*). XRD results confirmed that forsterite phase was found as a main phase in the ceramic powder. However, the forsterite phase decreased with increased concentration of Co to x = 0.8–1.6. This could be because of the solubility limit of Co in solid solution. In addition, the use of mirror waste as a raw material was able to reduce calcination temperature compared to the use of oxide reagents. Color measurements or CIEL*a*b* color space of forsterite pigments were located in red-blue quadrant for Co-doped pigment.

One-pot synthesis of highly fluorescent amino-functionalized graphene quantum dots for effective detection of copper ions

In this work, a green and simple one-pot route was developed for the synthesis of highly fluorescent amino-functionalized graphene quantum dots (a-GQDs) via hydrothermal process without any further modification or surface passivation. We synthesized the a-GQDs using glucose as the carbon source and ammonium as a functionalizing agent without the use of a strong acid, oxidant, or other toxic chemical reagent. The as-obtained a-GQDs have a uniform size of 3–4 nm, high contents of amino groups, and show a bright green emission with high quantum yield of 32.8%. Furthermore, the a-GQDs show effective fluorescence quenching for Cu2+ ions which can serve as effective fluorescent probe for the detection of Cu2+. The fluorescent probe using the obtained a-GQDs exhibits high sensitivity and selectivity toward Cu2+ with the limit of detection as low as 5.6 nM. The mechanism of the Cu2+ induced fluorescence quenching of a-GQDs can be attributed to the electron transfer by the formation of metal complex between Cu2+ and the amino groups on the surface of a-GQDs. These results suggest great potential for the simple and green synthesis of functionalized GQDs and a practical sensing platform for Cu2+ detection in environmental and biological applications.

Effect of Fenton-like oxidation reagent on hydrophobicity and floatability of chalcopyrite and molybdenite

A fundamental study is provided in this work to understand the effect of Fenton-like reagent made by the addition of FeSO4 in H2O2 aqueous solution on surface hydrophobicity and floatability of chalcopyrite (CuFeS2) and molybdenite (MoS2). Contact angle measurements were performed to assess the surface hydrophobicity. The contact angle results showed that Fenton-like reagent could alter the surface hydrophobicity of chalcopyrite at lower concentration of H2O2 aqueous solution compared to that of using H2O2 aqueous solution. On the other hand, molybdenite surface remained hydrophobic after the oxidation treatments using Fenton-like reagent and H2O2 aqueous solution. Surface characterizations using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) shows that the chalcopyrite surface covered with a thicker layer of oxidation products after the oxidation treatment using Fenton-like reagent, indicating a stronger surface oxidation. Flotation results were in agreement with contact angle results, showing that Fenton-like reagent could depress the floatability of chalcopyrite at lower concentration of H2O2 aqueous solution. On the other hand, molybdenite recovery remained high under various oxidation treatments owing to low surface oxidation.

Synthesis and glutathione reductase inhibitory properties of 5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one's aryl Schiff base derivatives.

Glutathione reductase (GR) is responsible for the existence of the reduced glutathione (GSH) molecule, a crucial antioxidant against oxidative stress reagents. The antimalarial activities of some redox active compounds are attributed to their inhibition of antioxidant flavoenzyme GR, and inhibitors are therefore expected to be useful for the treatment of malaria. In this work, a fast and effective synthesis and the GR inhibitory properties of 5-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one's aryl Schiff base derivatives are reported. For this aim, the triazol nucleus was obtained, which was substituted with identical groups: ester, hydrazide, and Schiff base system at the N-2 and N-4 nitrogen atoms. The majority of the reactions were carried out by utilizing both microwave and conventional methods in order to compare their yields and reaction times. Beside this, the occuring E/Z geometrical isomers from the CN double bond and the cis/trans amide conformers at the CONH single bond were studied. In the biological activity section of this work, it was found that all synthesized compounds have better inhibitory activity than N,N-bis(2-chloroethyl)-N-nitrosourea against GR; especially, two molecules, 6e and 6f, are the best among them. The evidence indicates that these Schiff base derivatives, with triazole ring, are strong GR inhibitors and novel antimalaria candidates.

Effect of Oxidation Agents on Photo-Decolorization of Vitamin B<sub>12</sub> in the Presence of ZnO/UV-A System

The aim of this work was to apply the many various oxidation agents namely H2O2, K2S2O8 and Fe2+ on the aqueous solution of vitamin B12 with the presence of ZnO. The results indicated that the use of the mixture of H2O2 and K2S2O8 in suspension of vitamin B12 and ZnO gave a maximum efficiency percentage about 95.85% in 12 min; it was higher than that without the addition of oxidation reagent 79.33% in the same time. The obtained results demonstrated that the activation energy for this photoreaction without the addition of oxidation agent was more than that the apparent activation energy value with the used mixture of H2O2 and K2S2O8. The thermodynamic study showed that both reactions were endothermic, less-random and non-spontaneous. The ΔH# with the oxidant agents (31.43 kJ mol-1) is less than that without using oxidant agents (35.81 kJ mol-1). Moreover, the addition of series of oxidant agent solution to vitamin B12 solution led to change the photocatalytic activity for decolorization of vitamin B12 in suspension solution of ZnO, and was found the activity sequence as follows: (H2O2 + K2S2O8) > (H2O2 + Fe(II)) (Fenton reaction) > (H2O2) > (K2S2O8) > (without the oxidation agents) > (K2S2O8 + Fe(II)) > Fe(II).

Protective effects of cichoric acid on H2O2-induced oxidative injury in hepatocytes and larval zebrafish models

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease with a broad spectrum of liver injury. Oxidant stress is believed to be the pathogenesis of NAFLD as the “second hit”. Hydrogen peroxide is widely used as an oxidant reagent to induce the oxidant injury of cells and larval zebrafish. Recently, cichoric acid is being studied extensively for its obesity attenuating, hepatic steatosis reduction and anti-oxidant effects. In this study, to identify whether CRA could protect the H2O2 induced oxidant injury via anti-oxidant impact by using L02 and HepG2 hepatocytes as in vitro and larval zebrafish as in vivo injury models, and evaluated the protective and anti-oxidant effects of CRA by pretreated it on both in vitro and in vivo models. CRA was found to reduce the production of ROS and MDA, activate the anti-oxidant enzymes SOD and GSH-px, and pathways Keap1-Nrf2 and HO-1. These results demonstrated that CRA might protect the liver injury by its anti-oxidant effect, which could be a potential therapeutic agent of NAFLD.

Revealing the architecture of protein complexes by an orthogonal approach combining HDXMS, CXMS, and disulfide trapping.

Many cellular functions necessitate structural assemblies of two or more associated proteins. The structural characterization of protein complexes using standard methods, such as X-ray crystallography, is challenging. Herein, we describe an orthogonal approach using hydrogen-deuterium-exchange mass spectrometry (HDXMS), cross-linking mass spectrometry (CXMS), and disulfide trapping to map interactions within protein complexes. HDXMS measures changes in solvent accessibility and hydrogen bonding upon complex formation; a decrease in HDX rate could account for newly formed intermolecular or intramolecular interactions. To distinguish between inter- and intramolecular interactions, we use a CXMS method to determine the position of direct interface regions by trapping intermolecular residues in close proximity to various cross-linkers (e.g., disuccinimidyl adipate (DSA)) of different lengths and reactive groups. Both MS-based experiments are performed on high-resolution mass spectrometers (e.g., an Orbitrap Elite hybrid mass spectrometer). The physiological relevance of the interactions identified through HDXMS and CXMS is investigated by transiently co-expressing cysteine mutant pairs, one mutant on each protein at the discovered interfaces, in an appropriate cell line, such as HEK293. Disulfide-trapped protein complexes are formed within cells spontaneously or are facilitated by addition of oxidation reagents such as H2O2 or diamide. Western blotting analysis, in the presence and absence of reducing reagents, is used to determine whether the disulfide bonds are formed in the proposed complex interface in physiologically relevant milieus. The procedure described here requires 1-2 months. We demonstrate this approach using the β2-adrenergic receptor-β-arrestin1 complex as the model system.

Waste control by waste: efficient removal of bisphenol A with steel slag, a novel activator of peroxydisulfate

Activated persulfates are efficient reagents for oxidation of organic contaminants and water treatment. Various compounds are currently used to activate persulfates, but there is a need for cheap and efficient activators. Here, we report the first use of steel slag, an industrial solid waste, as a solid activator for peroxydisulfate activation. We tested this system for bisphenol A degradation. Results indicate that about 70% of bisphenol A can be removed within 1 h. Conditions were 50 μg/L of bisphenol A, 2 g/L of peroxydisulfate, 3 g/L of steel slag and temperature of 298 K. The components and surface morphology of unused and recycled steel slag were analyzed by X-ray diffraction and scanning electron microscopy, whereas the main reactive oxygen species were elucidated by using radical scavengers. Findings show that both base oxides and iron oxides are responsible for peroxydisulfate activation. A redox mechanism involving liquid and solid phases is proposed. Overall, this study reveals the successful recycling of steel slag to activate persulfates for water treatment, following the principle of ‘waste control by waste.’