Search

The exhaustion of conventional light oils necessitates the shift towards unconventional sources such as biomass, heavy oil, oil shale, and coal. Non-catalytic thermal cracking by a free radical mechanism is at the heart of the upgrading, prior to refining into valuable products. However, thermal pyrolysis is hindered by the formation of asphaltenes, precursors to coke, limiting cracking, causing equipment fouling, and reducing product stability. Free radicals are inherently present in heavy fractions and are generated during thermal processes. This makes these reactive intermediates central to understanding these mechanisms and limiting coking. Electron spin resonance (ESR) spectroscopy facilitates such mechanistic studies. Over the past decade, there has been no review of using in-situ ESR for studying thermal processes. This work begins with a brief description of free radicals' chain reactions during thermal reactions and the wealth of information ESR provides. We then critically review the literature that uses ESR for mechanistic studies in thermal pyrolysis of biomass, heavy oil, shales, and coal. We conclude that limited literature exist, and more investigations are necessary. The key findings from existing literature are summarized to know the current state of knowledge. We also explicitly highlight the research gaps. [ABSTRACT FROM AUTHOR]

MXenes, a promising family of 2D transition metal carbides/nitrides, are renowned for their exceptional electronic conductivity and mechanical stability, establishing them as highly desirable candidates for advanced electromagnetic interference (EMI) shielding material. Despite these advantages, challenges persist in optimizing MXene synthesis methods and improving their oxidation resistance. Surface defects on MXenes significantly impact their electronic properties, impeding charge transport and catalyzing the oxidation process. In this study, a novel synthesis protocol derived from the conventional, minimally invasive layer delamination (MILD) method, is presented. Two additional steps are introduced aiming at enhancing process yield, addressing a crucial issue as conventional methods often yield high‐quality individual MXene flakes but struggle to generate sufficient quantities for bulk material production. This approach successfully yields Ti3C2Tx films with excellent conductivity (3973.72 ±121.31 Scm−1) and an average EMI shielding effectiveness (SE) of 56.09 ± 1.60 dB within the 1.5 to 10 GHz frequency range at 35% relative humidity (RH). Furthermore, this investigation delves into the long‐term oxidation stability of these films under varying RH conditions. These findings underscore the effectiveness of this innovative synthesis approach in elevating both the conductivity and EMI shielding capabilities of MXene materials. This advancement represents a significant step toward harnessing MXenes for practical applications requiring robust EMI shielding solutions. Additionally, insights into long‐term stability offer critical considerations for implementing MXenes in real‐world environments. [ABSTRACT FROM AUTHOR]

Introduction: Electrostatic binding of deoxyhemoglobin (Hb) to cytoplasmic domain of band 3 anion transport protein occurs as part of the glycolytic regulation in red blood cells (RBCs). Hb oxidation intermediates not only impact RBC's oxygenation but also RBC's membrane through the interaction with band 3. It is not known however whether these critical pathways undergo changes during the storage of RBCs. Methods and Results: Oxygen parameters of fresh blood showed a sigmoidal and cooperative oxygen dissociation curve (ODC) for the first week of storage. This was followed by a large drop in oxygen affinity (P50) (from 30 to 20 mmHg) which remained nearly unchanged with a slight elevation in Bohr coefficients and a significant drop in extracellular acidification rates (ECAR) at the 42-day storage. Oxidation of Hb increased with time as well as the formation of a highly reactive ferryl Hb under oxidative stress conditions. Ferryl Hb interacted avidly with RBC's membrane's band 3, but to lesser extent with old ghost RBCs. Discussion: The observed alterations in RBC's oxygen binding may have been affected by the alterations in band 3's integrity which are largely driven by the internal iron oxidation of Hb. Restoring oxygen homeostasis in stored blood may require therapeutic interventions that target changes in Hb oxidation and membrane changes. [ABSTRACT FROM AUTHOR]

Abstract MXenes, a promising family of 2D transition metal carbides/nitrides, are renowned for their exceptional electronic conductivity and mechanical stability, establishing them as highly desirable candidates for advanced electromagnetic interference (EMI) shielding material. Despite these advantages, challenges persist in optimizing MXene synthesis methods and improving their oxidation resistance. Surface defects on MXenes significantly impact their electronic properties, impeding charge transport and catalyzing the oxidation process. In this study, a novel synthesis protocol derived from the conventional, minimally invasive layer delamination (MILD) method, is presented. Two additional steps are introduced aiming at enhancing process yield, addressing a crucial issue as conventional methods often yield high‐quality individual MXene flakes but struggle to generate sufficient quantities for bulk material production. This approach successfully yields Ti3C2Tx films with excellent conductivity (3973.72 ±121.31 Scm−1) and an average EMI shielding effectiveness (SE) of 56.09 ± 1.60 dB within the 1.5 to 10 GHz frequency range at 35% relative humidity (RH). Furthermore, this investigation delves into the long‐term oxidation stability of these films under varying RH conditions. These findings underscore the effectiveness of this innovative synthesis approach in elevating both the conductivity and EMI shielding capabilities of MXene materials. This advancement represents a significant step toward harnessing MXenes for practical applications requiring robust EMI shielding solutions. Additionally, insights into long‐term stability offer critical considerations for implementing MXenes in real‐world environments.

Introduction: Electrostatic binding of deoxyhemoglobin (Hb) to cytoplasmic domain of band 3 anion transport protein occurs as part of the glycolytic regulation in red blood cells (RBCs). Hb oxidation intermediates not only impact RBC’s oxygenation but also RBC’s membrane through the interaction with band 3. It is not known however whether these critical pathways undergo changes during the storage of RBCs.Methods and Results: Oxygen parameters of fresh blood showed a sigmoidal and cooperative oxygen dissociation curve (ODC) for the first week of storage. This was followed by a large drop in oxygen affinity (P50) (from 30 to 20 mmHg) which remained nearly unchanged with a slight elevation in Bohr coefficients and a significant drop in extracellular acidification rates (ECAR) at the 42-day storage. Oxidation of Hb increased with time as well as the formation of a highly reactive ferryl Hb under oxidative stress conditions. Ferryl Hb interacted avidly with RBC’s membrane’s band 3, but to lesser extent with old ghost RBCs.Discussion: The observed alterations in RBC’s oxygen binding may have been affected by the alterations in band 3’s integrity which are largely driven by the internal iron oxidation of Hb. Restoring oxygen homeostasis in stored blood may require therapeutic interventions that target changes in Hb oxidation and membrane changes.

The first bentonite catalyst for oxidation of sulfides and oxidative coupling of thiols was fabricated. This novel catalyst was included natural bentonite, extracted cellulose from wheat wastes, and vanadium complex (Cell/Bent@V nanocomposite). It was characterized using SEM, TEM, ICP, AFM, XRD, XPS, and FT-IR. Further, oxidation of primary and secondary of alcohols were considered to show its catalytic potential for the various substrates. High yield, excellent conversion, and selectivity were observed for oxidation reactions catalyzed by Cell/Bent@V nanocomposite. Cel/Ben/V nanocomposite was shown the excellent stability and activity confirming by SEM, XRD, and FT-IR of recycled catalyst. Finally, the effect of ultrasonic irradiation instead of stirring on the oxidation reaction was evaluated. The high yields and conversions in the less times were observed.

Methods for carrying out coupling reactions in the chemistry of alkynes to form C–C bonds (oxidative dehydrocondensation reactions, Cadiot–Chodkiewicz reaction, and Sonogashira reaction) are analyzed and generalized. Protocols of synthesis of products of these reactions are also presented, including homogeneous and heterogeneous catalytic systems. In all cases, emphasis is placed on the kinetics and mechanisms of reactions with the discussion of the results of kinetic and spectrometric studies of the mechanisms of coupling reactions involving Cu(I, II, III), Au(I, III), Pd(0, I, II), and Fe (0, I, II, III) complexes. Particular attention is paid to the heterogeneous catalysis of oxidation reactions of alkynes with the participation of nanoparticles and nanoclusters of Pd, Au, Ag, and other metals. The nature of the intermediates containing these metals and the relationships between various oxidative and nonoxidative transformations of alkynes are discussed. [ABSTRACT FROM AUTHOR]

Polyethylene has become an integral part of our contemporary lives. The neoteric versatile nature of polyethylene is used in constructing various applications. Out of the plastic waste discarded, 60% of the plastic waste enters landfills. The polyethylene discarded in the soil and water on exposure to the environment forms macroplastics (>2.5 cm), mesoplastics (5 mm - 2.5 cm) and microplastics (<5 mm). Microplastics in the water and soil are observed to have lethal and ecotoxicological effects on aquatic and terrestrial organisms. They enter the food chain and permeate into the food that one eats. In order to address this impending concern, the present study aimed to treat plastics to form a degradable, safe and earthy material. The dissolved polyethylene was treated with starch and was made to react with oxidizing agents such as hydrogen peroxide, nitric acid and acetic acid to lower its inert ability to withstand its degradation. The effect of starch and oxidizing agents on dissolved low density polyethylene was subsequently analysed. The analysis of treated polyethylene showed a decrease in its crystallinity percentage by 6.19 and an increase in its functional groups on reaction with solvent trichloroethylene made to react with starch and oxidizing agents. In the present research, tests were conducted to obtain the various methods that can be utilized to reverse the inert ability of polyethylene. The prevailing recycling model that uses antioxidation techniques is counterproductive since it was found that such techniques appeared to make the polyethylene more resistant to further degradation. In this study, the polyethylene was dissolved in the solvents, such as xylene and trichloroethylene, to make the polyethylene more susceptible to reactants and hence a viable model for treating polyethylene. [ABSTRACT FROM AUTHOR]

The synthesis of imines denotes a cornerstone in organic chemistry. The use of alcohols as renewable substituents for carbonyl-functionality represents an attractive opportunity. Consequently, carbonyl moieties can be in situ generated from alcohols upon transition-metal catalysis under inert atmosphere. Alternatively, bases can be utilized under aerobic conditions. In this context, we report the synthesis of imines from benzyl alcohols and anilines, promoted by KOtBu under aerobic conditions at room temperature, in the absence of any transition-metal catalyst. A detailed investigation of the radical mechanism of the underlying reaction is presented. This reveals a complex reaction network fully supporting the experimental findings. [ABSTRACT FROM AUTHOR]

Graphene is one of the most auspicious constituents in nanotechnology. It provides the most accurate theoretical 2‐D depiction of catalytic sustenance. Its exceptional, physico‐chemical, and mechanical qualities make it distinctive and also able to create composite materials with novel capabilities. Although using graphene as a single‐layered sheet as a catalytic tool has not been documented yet, certain encouraging outcomes using few‐layer graphene have previously been attained. We will quickly go through the most pertinent synthetic methods for obtaining graphene and graphene based materials in this article. The composites of graphene are used in various catalytic reactions, including Coupling reactions, Aza‐Michael addition, Hydration, Oxidation, Esterification, Pechmann Condensation, Knoevenagel Condensation, Ring‐Opening Polymerization, Friedel‐Crafts Addition, Ring Opening of Epoxides and Decarboxylation have been catalysed by these expertly crafted and prepared graphene‐based catalysts. The graphene based composites allows for easy, recyclable, arnold transform, and environmentally friendly photocatalysis and also mild, precise, and super effective conversions and synthesis. [ABSTRACT FROM AUTHOR]

An easy-to-handle eosin Y-based heterogeneous photocatalyst was prepared by post-functionalization of a polydopamine-coated open cell polyurethane foam (PDA@PUF) via the silanization of the adhesive layer with 3-(triethoxysilyl)propan-1-amine (APTES) and the subsequent EDC-mediated coupling of the resulting amino-functionalized foam with eosin Y. The obtained macroscopic material, EY-APTES@PDA@PUF, showed good efficiency and excellent reusability, in an easy-to-carry "dip-and-play" mode for at least six runs as photocatalyst for the aerobic oxidation of 2-methyl-5-nitroisoquinolin-2-ium iodide to the corresponding isoquinolone. Subsequent investigation of the catalytic efficiency of EY-APTES@PDA@PUF for the oxidation of sulfides to sulfoxides, however, evidenced non-negligible eosin Y leaching, leading to a progressive deactivation of the catalytic foam in this case. Two alternative synthetic protocols for the preparation of the macroscopic photocatalyst were next explored to avoid eosin Y leaching. In both cases however, cycling tests also highlighted a progressive deactivation of the catalytic foams in sulfide-to-sulfoxide oxidation reactions. [ABSTRACT FROM AUTHOR]

In this article, we show that tribromide heterogenized on the surface of silica-coated magnetic nanoparticles modified with N2,N4,N6-tris(aminomethyl)-1,3,5-triazine-2,4,6-triamine [Fe3O4@SiO2-tris(triazine-triamine)-Br3] is a novel and efficient reusable nanocatalyst for the oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides using hydrogen peroxide as green oxidant. The structure of the as-fabricated Fe3O4@SiO2-tris(triazine-triamine)-Br3 was characterized by a series of spectroscopic techniques including FT-IR spectroscopy, SEM, TEM, EDX, VSM, XRD and TGA techniques. TEM and SEM analysis confirmed that the typical silica shell thickness was assessed to be around 20 nm. Recycling studies revealed that the Fe3O4@SiO2-tris(triazine-triamine)-Br3 could be easily recovered by a simple magnetic separation and recycled at least 6 times without deterioration in catalytic activity. [ABSTRACT FROM AUTHOR]

This report presents the development of an inexpensive mesoporous nanocatalyst i.e. silica coated N -doped carbon modified with ruthenium nanoparticles (Ru/RuO 2 @NSAC). The carbon and nanosilica components were derived from waste materials namely waste tea extract and rice husk respectively highlighting the sustainable approach to the synthesis process. The nanocatalyst was thoroughly characterized using various advanced techniques such as Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (P-XRD), Field emission gun-scanning electron microscopy (FEG-SEM), Energy dispersive X-ray analysis (EDX), High resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray resonance fluorescence (XRF) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). These characterizations provided comprehensive insights into the structural features of the nanocatalyst. XPS analysis confirmed the presence of both metallic ruthenium and Ru (IV) on the nanocatalytic support. The particle size of Ru/RuO 2 @NSAC was determined using Scherrer's equation and came out to be 21.37 nm. This nanocatalyst demonstrated remarkable performance as a robust heterogeneous catalyst for the oxidation of alkylarenes and alcohols to their corresponding carbonyl compounds. It exhibited excellent recyclability, maintaining its activity for up to five consecutive runs. Post-recycling, the catalyst was again characterized by P-XRD and FEG-SEM to ensure its structural integrity. Additionally, the antibacterial activity of Ru/RuO 2 @NSAC was evaluated against both Gram-positive and Gram-negative bacteria. A density functional theory study was also conducted to support the experimental findings, providing a theoretical basis for the observed catalytic behavior. [Display omitted] • Hydrothermal synthesis of Ru/RuO 2 @NSAC nanocatalyst using waste tea leaves, rice husk as activated carbon and SiO 2 sources. • Ru/RuO 2 @NSAC characterized by various spectroscopy techniques and showed excellent recyclability. • Activated carbon showed antimicrobial activity and a DFT study of Ru/RuO2@NSAC was conducted to analyze bonding parameters. [ABSTRACT FROM AUTHOR]

The article deals with the recycling issues of electric steelmaking dusts by thermodynamic extraction of iron, zinc and lead in order to reduce the impact on the environment and increase the industry resource base.The purpose of the research was to determine the influence of the quantitative content of low-calorie and high-calorie carbon on the processes of zinc oxide reduction in gas purification dust and its further sublimation using a vacuum in a closed system of a resistance heating furnace. Determined the dependence of the zinc extraction degree and the increase of iron oxides in the samples studied.

The peroxymonocarbonate anion, HCO4−, the covalent adduct between the carbon dioxide and hydrogen peroxide anion, effectively reacts with SO2 in the gas phase following three oxidative routes. Mass spectrometric and electronic structure calculations show that sulphur dioxide is oxidised through a common intermediate to the hydrogen sulphate anion, sulphur trioxide, and sulphur trioxide anion as primary products through formal HO2−, oxygen atom, and oxygen ion transfers. The hydrogen sulphite anion is also formed as a secondary product from the oxygen atom transfer path. The uncommon nucleophilic behaviour of HCO4− is disclosed by the Lewis acidic properties of SO2, an amphiphilic molecule that forms intermediates with characteristic and diagnostic geometries with peroxymonocarbonate. [ABSTRACT FROM AUTHOR]

VOx/SiO2 with different V/Si atomic ratios have been synthesized by hydrothermal method from alkoxides of vanadium and silicon compounds. The prepared samples are characterized by high specific surface area (300-700 m2/g), uniform nanodispersed distribution of vanadia in silica matrix, the absence of crystalline phases, and the absence of the band typical for V=O bond in the Raman spectra. High activity and selectivity of the synthesized catalysts in oxidation of methane to formaldehyde, oxy-dehydrogenation of propane and n-butane have been established. [ABSTRACT FROM AUTHOR]

Accurate calculation of rate constants for gas-phase OH-oxidation reactions of fluorinated compounds is crucial for the understanding of atmospheric processes that are subject of the Kigali Agreement. Here, we have determined two such rate constants for two hydrofluoroketones, HFK-447mcc and HFK-465mc. The calculations were performed with a cost-effective multiconformer transition state theory protocol coupled with the constrained transition state randomization sampling method. The calculated rate constants of k (HO • + HFK - 447 mcc) = 3.1 × 10 − 15 cm 3 molecule − 1 s − 1 and k (HO • + HFK - 465 mc) = 3.2 × 10 − 14 cm 3 molecule − 1 s − 1 at 298.15 K imply an atmospheric lifetime of 10 years and 1 year, respectively. To our knowledge, these rate constants have never been determined experimentally or theoretically, and the similarity between the ratios of these two rate constants and of the well-studied acetone and diethyl ketone suggest the validity of our approach toward obtaining accurate rate constants and branching ratios. [ABSTRACT FROM AUTHOR]

Todays, the heteroatom-doped mesoporous carbon resulting from Metal-Organic Framework (MOF) has attracted the substantial consideration in various filed especially in the heterogeneous catalytic protocols due to their adaptable features. These materials have a high Specific Surface Area (SSA), which offers copious activated sites for the catalytic activity. The mesoporous nature also simplifies the effectual mass transfer, thereby amplifying the overall catalytic procedure. In this study, a highly effective Zr@NC-T samples were synthesized via pyrolyzing a composite of g-C 3 N 4 and UiO-66. The mesoporous structure of Zr@NC-T, revealed a desired SSA varying from 591.38 to 404.26 m2.g−1 due to its surface defect and disorder. Among the synthesized catalysts, Zr@NC-700 (pyrolyzed at 700 °C) exposed preferred catalytic proficiency in the selective oxidation of BnOHs to BnCHO due to its higher surface defect which is caused the higher SSA and structure defect. Furthermore, the Zr@NC-700 catalyst as well proved the acceptable chemical stability due to its reusability. [Display omitted] [ABSTRACT FROM AUTHOR]

Partial oxidation of some organics is desirable in some scenarios for compensation of the heat required for pyrolysis, which, however, impacts not only composition of bio-oil but also possibly property of biochar. This was investigated herein by oxidative pyrolysis of poplar sawdust from 300 to 600 °C and further analysis of the pyrolytic products, especially biochar. The results showed that O 2 could oxidize some organics on surface of biochar, forming more volatiles below 400 °C. Above this temperature the excessive oxidation of the light and heavy organics with π-conjugated structures in bio-oil dominated, producing more gases. Weight loss of biochar from oxidation of organics on its surface was only remarkable at 300 °C, while some weight gain was observed from introduction of additional oxygen-containing functionalities from the oxidation. The removal of aromatic structures on biochar at 500 or 600 °C via oxidation was rather difficult. However, the oxidation reactions did make the biochar oxygen-rich but hydrogen-deficient, which, in overall, improved thermal stability and comprehensive combustion performance of the biochar. Additionally, oxygen presence enhanced aromatic degree of biochar by increasing regularity of (100) facet of carbon crystals while narrowing interplanar spacing of (002) facets. The oxygen-rich nature also made the biochar from the oxidative pyrolysis more hydrophilic while the removal of some organics via oxidation promoted development of the pore structures. • 400 °C is a boundary temperature for oxidation of organics on biochar to bio-oil or further oxidation to gases. • Oxidation makes biochar O-rich but H-deficient, due to preferential oxidation of H. • Oxidation improves regularity of carbon crystals while narrows interplanar spacing of (002) facets. • Oxidation improves combustion, thermostability, and development of pore of biochar. [ABSTRACT FROM AUTHOR]

Non-enantioselective alcohol dehydrogenases (ADHs) are rarely found in the biocatalysis portfolio. Generally, highly enantioselective ADHs are sought for. Using such ADHs for the oxidation of racemic alcohols generally results in a kinetic resolution of the starting material, which is unfavourable if the ketone represents the product of interest. In the current contribution we report the ADH from Sphingobium yanoikuyae (SyADH) as non-enantioselective ADH for the complete oxidation or rac-heptan-2-ol (representing further 2-alkanols). [ABSTRACT FROM AUTHOR]

Alcohol dehydrogenases (ADHs) have become important catalysts for stereoselective oxidation and reduction reactions of alcohols, aldehydes and ketones. The aim of this contribution is to provide the reader with a timely update on the state-of-the-art of ADHcatalysis. Mechanistic basics are presented together with practical information about the use of ADHs. Current concepts of ADH engineering and ADH reactions are critically discussed. Finally, this contribution highlights some prominent examples and futurepointing concepts. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals were prepared and used as photocatalysts for the in situ 1O2 generation to perform hetero Diels–Alder, ene and oxidation reactions with suitable dienes and alkenes. The methodology has been reasonably standardized and made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated by the results in all the tested reactions, which allowed to obtain desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed especially in the case of the alkene oxidations as well as poor chemoselectivity was somewhere observed. 1O2 generated by lead halide perovskite nanocrystals as photocatalyst in organic reactions. [ABSTRACT FROM AUTHOR]

Abstract As a prominent member of the vitamin E group, α‐tocopherol is an important lipophilic antioxidant. It has a special oxidation chemistry that involves phenoxyl radicals, quinones and quinone methides. During the oxidation to the ortho‐quinone methide, an intermediary zwitterion is formed. This aromatic intermediate turns into the quinone methide by simply rotating the initially oxidized, exocyclic methyl group into the molecule's plane. This initial zwitterionic intermediate and the quinone methide are not resonance structures but individual species, whose distinct electronic structures are separated by a mere 90° bond rotation. In this work, we hindered this crucial rotation, by substituting the affected methyl group with alkyl or phenyl groups. The alkyl groups slowed down the conversion to the quinone methide by 18‐times, while the phenyl substituents, which additionally stabilize the zwitterion electronically, completely halted the conversion to the quinone methide at −78 °C, allowing for the first time the direct observation of a tocopherol‐derived zwitterion. Employing a 13C‐labeled model, the individual steps of the oxidation sequence could be observed directly by NMR, and the activation energy for the rotation could be estimated to be approximately 2.8 kcal/mol. Reaction rates were solvent dependent, with polar solvents exerting a stabilizing effect on the zwitterion. The observed effects confirmed the central relevance of the rotation step in the change from the aromatic to the quinoid state and allowed a more detailed examination of the oxidation behavior of tocopherol. The concept that a simple bond rotation can be used to switch between an aromatic and an anti‐aromatic structure could find its use in molecular switches or molecular engines, driven by the specific absorption of external energy.

Abstract Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na12Ge17 as a model system containing redox‐sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3‐trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na12Ge17 observed on long‐time contact with such ILs was not caused by dissolution of the salt‐like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na+ ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na12Ge17 were initiated, transferring a considerable part of Na+ into solution. At optimized conditions, an X‐ray amorphous product NaGe6.25 was obtained, which was thermally convertible to the crystalline type‐II clathrate Na24–δGe136 with almost completely Na‐filled polyhedral cages, and α‐Ge. The presented method thus provides unexpected access to Na24–δGe136 in bulk quantities.

Non-enantioselective alcohol dehydrogenases (ADHs) are rarely found in the biocatalysis portfolio. Generally, highly enantioselective ADHs are sought for. Using such ADHs for the oxidation of racemic alcohols generally results in a kinetic resolution of the starting material, which is unfavourable if the ketone represents the product of interest. In the current contribution we report the ADH from Sphingobium yanoikuyae (SyADH) as non-enantioselective ADH for the complete oxidation or rac-heptan-2-ol (representing further 2-alkanols).

Alcohol dehydrogenases (ADHs) have become important catalysts for stereoselective oxidation and reduction reactions of alcohols, aldehydes and ketones. The aim of this contribution is to provide the reader with a timely update on the state-of-the-art of ADH-catalysis. Mechanistic basics are presented together with practical information about the use of ADHs. Current concepts of ADH engineering and ADH reactions are critically discussed. Finally, this contribution highlights some prominent examples and future-pointing concepts.

Mayenite (12CaO·7Al2O3) is a mesoporous calcium aluminum oxide, with a characteristic crystalline structure. The framework of mayenite is composed of interconnected cages with a positive electric charge per unit cell that includes two molecules [Ca24Al28O64]4+, and the remaining two oxide ions O2−, often labelled "free oxygen", are trapped in the cages defined by the framework. Starting from mayenite structure several derivatives have been prepared through advanced synthetic protocols by free oxygen substitution with various anions. Mayenite and its derivates have been intensively investigated in many applications which include catalysis (oxidation and reduction, ammonia synthesis, pinacol coupling), environmental sensors and CO2 sorbent materials. In this review, we summarize our recent results on the main applications of mayenite and its derivatives. [ABSTRACT FROM AUTHOR]

Vanadium oxyphosphate (VPO) with a high surface area was synthesized in a mixed solvent of ionic liquid [Bmim]Br and water, using phosphorous acid to reduce V5+ to V4+ and as a partial phosphorus source, and V2O5 as the vanadium source. The effects of ionic liquids on the synthesis process were investigated in detail. Using pure water as the solvent, the product was a vanadium phosphate compound with large flakes. With the increase in the amount of ionic liquid, the size of the large flakes of vanadium phosphate gradually decreased, and the morphology was changed to spherical particles. When the proportion of ionic liquid was 80% or the ionic liquid was solely used as the solvent, the VPO showed completely spherical particle morphology, and the specific surface area was the highest. X-ray diffraction analysis showed that the crystal phase of VPO changed from vanadium (IV) hydrogenphosphate hemihydrate (VOHPO4·0.5H2O) to an amorphous state with an increase in ionic liquid ratio. All of the above results show that ionic liquids play an important role in the synthesis of VPO materials. After being calcined in an n-butane/air atmosphere, the precursors were transformed into the vanadium pyrophosphate phase. The active VPO catalysts were used in the selective oxidation of cyclohexanol, and the yield of cyclohexanone was 57.98% for the VPO-80 catalyst synthesized using the ionothermal method but only 21.41% for the VPO-W catalyst synthesized using a traditional hydrothermal method, which shows the advantage of ionic liquid synthesis for VPO catalysts. Vanadium oxyphosphate material with high surface area was synthesized in the mixed solvent of ionic liquid [Bmim]Br and water. Ionic liquid plays an important role in the morphology and properties of synthesized VPO materials. The active VPO catalysts were used in the selective oxidation of cyclohexanol, and the yield of cyclohexanone was 57.98% for VPO-80 catalyst synthesized by ionothermal method, but only 21.41% for VPO-W catalyst synthesized by traditional hydrothermal method, which exhibited the advantages of ionic liquid synthesis for VPO catalysts. [ABSTRACT FROM AUTHOR]

Subnanoparticles (SNPs) with sizes of approximately 1 nm are attractive for enhancing the catalytic performance of transition metals and their oxides. Such SNPs are of particular interest as redox‐active catalysts in selective oxidation reactions. However, the electronic states and oxophilicity of copper oxide SNPs are still a subject of debate in terms of their redox properties during oxidation reactions for hydrocarbons. In this work, in situ X‐ray absorption fine structure (XAFS) measurements of Cu28Ox SNPs, which were prepared by using a dendritic phenylazomethine template, during temperature‐programmed reduction (TPR) with H2 achieved lowering of the temperature (T50=138 °C) reported thus far for the CuII→CuI reduction reaction because of Cu−O bond elongation in the ultrasmall copper oxide particles. [ABSTRACT FROM AUTHOR]

This work shows the biosynthesis of gold clusters and nanoparticles (AuNPs) from a solution of gold in a mixture of ammonium chloride and nitric acid treated with two different Mexican plants extracts, Toad Leaf (Eryngium heterophyllum, SF) and Cuachalalate (Amphipterygium adstringens, CF) as bioreductants. Subsequently, the gold entities were supported on the ordered mesoporous material SBA-15 functionalized with mercaptopropyl groups (1.6 wt% of sulphur). The gold contents were 0.7 wt% and 1.1 wt% for the CF and SF samples, respectively. UV–vis spectroscopy and TEM show the presence of gold nanoclusters in both samples, while very minor amount of AuNPs is detected only in the sample with the highest Au content (SF). The Au/SBA-15 materials are active in the aerobic oxidation of cyclohexene at 65 °C and atmospheric pressure. Two of the catalytic reaction products come from the addition of oxygen to the double bond of cyclohexene: cyclohexene epoxide and cyclohexanediol, while the other three come from allylic oxidation of the ring, which is the major reaction pathway: 2-cyclohexen-1-ol, 2-cyclohexen-1-one and 2-cyclohexenyl hydroperoxide, being the two first the major stable reaction products, while the enone/enol ratio is nearly 2. It has been found that the gold nanoclusters initially present in the catalysts evolve toward AuNPs during catalytic reaction. [ABSTRACT FROM AUTHOR]

As a prominent member of the vitamin E group, α‐tocopherol is an important lipophilic antioxidant. It has a special oxidation chemistry that involves phenoxyl radicals, quinones and quinone methides. During the oxidation to the ortho‐quinone methide, an intermediary zwitterion is formed. This aromatic intermediate turns into the quinone methide by simply rotating the initially oxidized, exocyclic methyl group into the molecule's plane. This initial zwitterionic intermediate and the quinone methide are not resonance structures but individual species, whose distinct electronic structures are separated by a mere 90° bond rotation. In this work, we hindered this crucial rotation, by substituting the affected methyl group with alkyl or phenyl groups. The alkyl groups slowed down the conversion to the quinone methide by 18‐times, while the phenyl substituents, which additionally stabilize the zwitterion electronically, completely halted the conversion to the quinone methide at −78 °C, allowing for the first time the direct observation of a tocopherol‐derived zwitterion. Employing a 13C‐labeled model, the individual steps of the oxidation sequence could be observed directly by NMR, and the activation energy for the rotation could be estimated to be approximately 2.8 kcal/mol. Reaction rates were solvent dependent, with polar solvents exerting a stabilizing effect on the zwitterion. The observed effects confirmed the central relevance of the rotation step in the change from the aromatic to the quinoid state and allowed a more detailed examination of the oxidation behavior of tocopherol. The concept that a simple bond rotation can be used to switch between an aromatic and an anti‐aromatic structure could find its use in molecular switches or molecular engines, driven by the specific absorption of external energy. [ABSTRACT FROM AUTHOR]

In this paper, we report the fabrication and characterization of a stable heterogeneous nanostructure catalyst of copper immobilized on Fe3O4@SiO2@l-Arginine, for the oxidation of sulfides and oxidative coupling of thiols. The prepared nanocatalyst has been characterized by different techniques such as FTIR, XRD, SEM, TEM and TGA. These nanoparticles were the effective catalyst for selective oxidation of sulfides and oxidative coupling of thiols using 30% H2O2. The suggested method offers several prominent advantages such as mild condition, use of magnetically reusable catalyst, simple workup procedure, good to high yields of products and great selectivity. [ABSTRACT FROM AUTHOR]

Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na12Ge17 as a model system containing redox‐sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3‐trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na12Ge17 observed on long‐time contact with such ILs was not caused by dissolution of the salt‐like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na+ ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na12Ge17 were initiated, transferring a considerable part of Na+ into solution. At optimized conditions, an X‐ray amorphous product NaGe6.25 was obtained, which was thermally convertible to the crystalline type‐II clathrate Na24–δGe136 with almost completely Na‐filled polyhedral cages, and α‐Ge. The presented method thus provides unexpected access to Na24–δGe136 in bulk quantities. [ABSTRACT FROM AUTHOR]

A combined effect of pulsed electric field application and salting in a brine with 5 and 10% w/w NaCl on oxidative stability of lipids and proteins, as well as color characteristics of sea bass samples, was assessed in the study. The applied intensity of the current was set at 10 and 20 A corresponding to 300 and 600 V cm−1, respectively. Pulsed electric field (PEF) treatment led to a significant (p < 0.05) increase in primary and secondary lipid oxidation products expressed as peroxide value, conjugated dienes and 2-thiobarbituric acid reactive substances in PEF-treated samples compared to untreated ones. Conjugated dienes, as unstable primary oxidation products, correlated with b∗-value (p < 0.05, R = 0.789), suggesting their contribution to the yellowness of the fish flesh due to fast decomposition and conversion into secondary oxidation products yielding yellow pigmentation.However, none of the fish samples treated at the higher current intensity of 20 A exceeded the acceptable level of 5 meq active oxygen/kg lipid according to the requirements of the Standard for fish oils CODEX STAN 329–2017, suggesting acceptable oxidative status quality of sea bass samples after the treatment. PEF-treated fish samples also showed a significant increase in Schiff bases and total carbonyls on day 5 and day 8 of brine salting compared to non-treated samples, revealing a strong effect of electroporation on protein oxidation.

Encapsulated metalloporphyrins have been widely studied for their use as efficient heterogeneous catalysts, inspired by the known catalytic activity of porphyrins in haemoproteins. The oxidation of organic substrates by haemoproteins is one of the well-known roles of these proteins, in which the haem (ferriprotoporphyrin IX = FePPIX) cofactor is the centre of reactivity. While these porphyrins are highly efficient catalysts in the protein environment, once removed, they quickly lose their reactivity. It is for this reason that they have garnered much interest in the field of heterogeneous catalysis of oxidation reactions. This review details current research in the field, focusing on the application of encapsulated haem, and other synthetic metalloporphyrins, applied to oxidation reactions.

Abstract A practical method for generation of acylcyanides devoid of any external cyanide sources is presented that relies on a mild Ru‐catalyzed selective C−H‐oxidation of benzylic nitriles. The starting materials are smoothly generated through condensation of the corresponding carboxylic acid amides using silanes. The obtained acylcyanides can be employed in a plethora of transformation as exemplified to some larger extend in the sequence of C−H‐oxidation‐Tischenko‐rearrangement for the generation of structurally diverse benzoyloxycyanohydrines.

Inexpensive cobalt‐catalyzed oxidative C−H functionalization has emerged as a powerful tool for the construction of C−C and C−Het bonds, which offers unique potential for transformative applications to modern organic synthesis. In the early stage, these transformations typically required stoichiometric and toxic transition metals as sacrificial oxidants; thus, the formation of metal‐containing waste was inevitable. In contrast, naturally abundant molecular O2 has more recently been successfully employed as a green oxidant in cobalt catalysis, thus considerably improving the sustainability of such transformations. Recently, a significant momentum was gained by the use of electricity as a sustainable and environmentally benign redox reagent in cobalt‐catalyzed C−H functionalization, thereby preventing the consumption of cost‐intensive chemicals while at the same time addressing the considerable safety hazards related to the use of molecular oxygen in combination with flammable organic solvents. Considering the unparalleled potential of the aforementioned approaches for sustainable green synthesis, this Review summarizes the recent progress in cobalt‐catalyzed oxidative C−H activation until early 2020. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nanohybrid has been prepared as an ultrafast photocatalyst toward the selective generation of aldehydes under visible LED light. • Uniform dispersion of very small TiO 2 /CeCoO 3 /PMO-IL nanohybrid. • Easy separation of charge carriers and reduce their recombination rate. • The impressive stability of TiO 2 /CeCoO 3 /PMO-IL nanohybrid during the photocatalytic process. The construction of perovskite-based wide bandgap semiconductors with uniform dispersion is one of the main strategies to improve the catalytic activity of semiconductor materials. Here, a heterojunction catalyst was obtained by nucleating TiO 2 on CeCoO 3 nanopowders and producing TiO 2 /CeCoO 3 hetero nanostructures at 450 °C. Then by putting them on the PMO-IL as a porous substrate, TiO 2 /CeCoO 3 /PMO-IL nanohybrid was prepared. The properties of nanohybrid were characterized by FE-SEM, EDS, XRD, BET, XPS, HRTEM, SAED, FT-IR, DRS, and PL spectroscopy. The photocatalytic efficiency of TiO 2 /CeCoO 3 and TiO 2 /CeCoO 3 /PMO-IL toward the selective fabrication of aldehydes was studied under the irradiation of visible light. The synthesized nanohybrid demonstrated excellent catalytic activity compared to TiO 2 /CeCoO 3 and PMO-IL alone. Therefore, this nanohybrid could be used as a capable heterogeneous photocatalyst due to its high activity, selectivity, and recyclability. [ABSTRACT FROM AUTHOR]

The 2-oxoglutarate-dependent dioxygenase (2-OGD) superfamily is one of the largest protein families in plants. The main oxidation reactions they catalyze in plants are hydroxylation, desaturation, demethylation, epimerization, and halogenation. Four members of the 2-OGD superfamily, i.e., flavonone 3β-hydroxylase (F3H), flavones synthase I (FNS I), flavonol synthase (FLS), and anthocyanidin synthase (ANS)/leucoanthocyanidin dioxygenase (LDOX), are present in the flavonoid pathway, catalyzing hydroxylation and desaturation reactions. In this review, we summarize the recent research progress on these proteins, from the discovery of their enzymatic activity, to their functional verification, to the analysis of the response they mediate in plants towards adversity. Substrate diversity analysis indicated that F3H, FNS Ⅰ, ANS/LDOX, and FLS perform their respective dominant functions in the flavonoid pathway, despite the presence of functional redundancy among them. The phylogenetic tree classified two types of FNS Ⅰ, one mainly performing FNS activity, and the other, a new type of FNS present in angiosperms, mainly involved in C-5 hydroxylation of SA. Additionally, a new class of LDOXs is highlighted, which can catalyze the conversion of (+)-catechin to cyanidin, further influencing the starter and extension unit composition of proanthocyanidins (PAs). The systematical description of the functional diversity and evolutionary relationship among these enzymes can facilitate the understanding of their impacts on plant metabolism. On the other hand, it provides molecular genetic evidence of the chemical evolution of flavonoids from lower to higher plants, promoting plant adaptation to harsh environments.

The reactivity of [NaL·ClO2]− cluster anions (L = ClOx−; x = 0–3) with sulphur dioxide has been investigated in the gas phase by ion–molecule reaction experiments (IMR) performed in an in-house modified Ion Trap mass spectrometer (IT-MS). The kinetic analysis revealed that SO2 is efficiently oxidised by oxygen-atom (OAT), oxygen-ion (OIT) and double oxygen transfer (DOT) reactions. The main difference from the previously investigated free reactive ClO2− is the occurrence of intracluster OIT and DOT processes, which are mediated by the different ligands of the chlorite anion. This gas-phase study highlights the importance of studying the intrinsic properties of simple reacting species, with the aim of elucidating the elementary steps of complex processes occurring in solution, such as the oxidation of sulphur dioxide.

The present work addresses the development of an eco-friendly and cost-efficient protocol for the oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones by mechanical processing under air. Ball milling was shown to promote the quantitative conversion of a broad set of alcohols into carbonyl compounds with no trace of an over-oxidation to carboxylic acids. The mechanochemical reaction exhibited higher yields and rates than the classical, homogeneous, TEMPO-based oxidation.

Methacrolein oxide (MACR-oxide) is a four-carbon, resonance-stabilized Criegee intermediate produced from isoprene ozonolysis, yet its reactivity is not well understood. This study identifies the functionalized hydroperoxide species, 1-hydroperoxy-2-methylallyl formate (HPMAF), generated from the reaction of MACR-oxide with formic acid using multiplexed photoionization mass spectrometry (MPIMS, 298 K = 25 °C, 10 torr = 13.3 hPa). Electronic structure calculations indicate the reaction proceeds via an energetically favorable 1,4-addition mechanism. The formation of HPMAF is observed by the rapid appearance of a fragment ion at m/z 99, consistent with the proposed mechanism and characteristic loss of HO2 upon photoionization of functional hydroperoxides. The identification of HPMAF is confirmed by comparison of the appearance energy of the fragment ion with theoretical predictions of its photoionization threshold. The results are compared to analogous studies on the reaction of formic acid with methyl vinyl ketone oxide (MVK-oxide), the other four-carbon Criegee intermediate in isoprene ozonolysis.

• Advances in oxidations by polymer-supported palladium nanoparticles and complexes, are described. • Synthetic methods are highlighted for attaining the polymer-supported palladium catalysts. • Catalytic oxidation of alcohols, olefins, alkenes, carbon monoxide, etc. are presented. • Future challenges and opportunities on oxidation reactions using Pd catalysts, are discussed. This review describes the recent advances in the fabrication, characterization and applications of palladium nanoparticles (Pd NPs)/complexes supported on polymers. Nanostructured materials and NPs of various natures, shapes and sizes in combination with polymers, provide unique physicochemical properties and significant potential applications. An overview in catalysis encompassing the preparation of polymer-supported Pd nanocatalysts and Pd complexes for the oxidation of alcohols, olefins, alkenes, carbon monoxide, etc. is presented. Heterogeneous oxidation catalysis, a vital tool in chemical synthesis and transformations, includes the development of various synthetic strategies for the fabrication of Pd-based catalysts; eminent role played by polymer supports in the morphological and structural properties of the ensuing catalysts, is highlighted. [ABSTRACT FROM AUTHOR]