Monatshefte für Chemie / Chemical Monthly最新文献

The symmetric supercapacitors (SC) are electrochemical capacitors with higher energy density than conventional ones. Both their positive and negative electrodes contain the same type of electrode active material. Carbon xerogels are a kind of carbon material which properties can be designed, structurally and chemically, in order to fit the requirements for their final application. They possess tunable porosity, high purity, and electrical conductivity and are very relevant for their use as active material for electrodes in supercapacitors. In this study, the electrochemical properties of symmetric supercapacitors were compared by using a polymer Aquivion™ electrolyte membrane (as electrolyte and separator) and the common aqueous electrolyte (i.e., 1 M KOH). The membrane was previously exchanged to the K⁺-form by immersion in 1 M KOH. The electrode active material was an activated carbon xerogel (AX-1500) prepared by polymerization of resorcinol and formaldehyde in a sol–gel microwave-assisted process. Electrochemical tests were carried out by cyclic voltammetry, galvanostatic charge/discharge measurements, impedance analysis, and long-term durability tests. The relationship between the structure and morphology of the carbon xerogel and the nature of the electrolyte was established, which may be relevant for the design of supercapacitors providing high power and energy densities.

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Cyclohexane (CHA), cyclohexene (CHE), and 1,4-cyclohexadiene (CHD) derivatives have a wide variety of applications and scope in synthetic and industrial organic chemistry. These cyclic hydrocarbons are found in a variety of natural products, including herbal plants and fruits as basic fragrance components. The extraction and isolation of these essential hydrocarbons are too complex and difficult to pursue. However, the reduction of benzene and its derivatives is an essential and effective approach for producing CHA, CHE, and CHD derivatives. To obtain CHA, CHE, and CHD derivatives, several types of reduction techniques for benzene and its derivatives have been developed over the years, including various forms of catalytic hydrogenation, Benkeser reduction, classic and many modified Birch reductions such as ammonia-free, metal-free photochemical, solvent-free, electrochemical and electride-mediated Birch reduction. In this study, the comparison of chemoselectivity, regioselectivity, reaction conditions, reduction efficiency, and environmentally acceptable approaches of these techniques used for benzene reduction are summarized.

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In applications such as mobile workstations during disaster relief operations, or specific military applications, the only energy sources used nowadays are gas or diesel generators, which could be replaced by more environmentally friendly renewable energy sources. The presented paper aims to provide insight into key elements and design principles for modular PV system design. Furthermore, two such proposed designs, which focus on modularity and mobility, are evaluated as a replacement for the generator-only solution that is used nowadays. We also propose ways of further optimization of the systems.

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The presented article deals with the creation of an own numerical model for the simulation of cyclic voltammetry in the field of electrochemistry. In practice, it is necessary to compare the result of voltammetry with the theoretical assumption to be able to obtain quantitative information from experiments. However, the electrochemical kinetics described by voltammetry is almost always a nonlinear transient problem. Apart from a few cases, an analytical solution is not possible and that is why computer simulation is necessary. The benefit of this work is the implementation of a more robust mathematical model in the ANSYS Fluent solver and the demonstration of its functionality.

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The use of fatty and aromatic acids as green acyl donors for enzymatic kinetic resolution via esterification of 1-phenylethanol and 1-phenylpropan-2-ol was described. The impact of the presence of magnesium sulfate on both reactivity and selectivity of Candida rugosa lipase (CRL) was checked. The organic solvents, the medium dilution, and the temperature revealed as determinant parameters to achieve enantioselective esterification reactions. A significant impact of the use of magnesium sulfate was revealed on the enantioselectivity of the CRL in heptane during the resolution of 1-phenylethanol, using butyric and lauric acids as acyl donors.

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Tetrahydropyridin-4-ylidene salts with benzyl and dibenzyl substitution showed good antiprotozoal activity. This paper reports the synthesis of analogues with longer side chains. They were investigated for their antiprotozoal activities as well as for their cytotoxicity using microplate assays. The most active compounds showed activity against Trypanosoma brucei rhodesiense in concentrations < 0.06 µM. A series of compounds was active against Plasmodium falciparum NF54 in low nanomolar concentration and exhibited outstanding selectivity. The influence of substitution pattern and chain length on the antiprotozoal potencies were analyzed and structure–activity relationships were given. New compounds were characterized by FT-IR, HRMS, and NMR spectroscopy.

In recent years, sugar alcohols have gained significant attention as organic phase change materials (PCMs) for thermal energy storage due to their comparably high thermal storage densities up to 350 J/g. In a computational study, outstandingly high values of up to ~ 450–500 J/g have been postulated for specific higher-carbon sugar alcohols. These optimized structures feature an even number of carbon atoms in the backbone and a stereochemical configuration in which all hydroxyl groups are in an 1,3-anti-relationship, as found in the natural hexitol d-mannitol. However, these manno-configured higher-carbon sugar alcohols have not been experimentally investigated as PCMs yet and described synthetic routes are elaborate multiple steps syntheses. Therefore, we aimed to synthesize sugar alcohols of the manno-series with a concise synthetic protocol based on the indium-mediated acyloxyallylation (IMA) of aldoses. En route the C2-epimers were easily accessible, namely gluco-configured sugar alcohols, bearing one set of hydroxyl groups in a suboptimal 1,3-syn-realtionship. The synthesized compounds were found to possess thermal properties consistent with the predicted values, and the “perfect” higher-carbon sugar alcohol with eight carbon atoms was found to have indeed an outstanding high latent heat of fusion of ~ 380 J/g with a melting point of 260 °C.

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To structurally characterize periodate-oxidized cellulosic substrates, methyl 4-O-methyl β-d-glucopyranoside and methyl 4’-O-methyl-cellobioside were subjected to periodate treatment at pH 4.8–5.0. Oxidation of the monosaccharide using two molar equivalents of oxidant produced 3-methoxy-2,5-dihydro-2-furanol as main product. To confirm its structure and mode of formation, 6-O-bisdeuteromethyl 4-O-methyl-β-d-glucopyranoside and methyl 4-O-trisdeuteromethyl-β-d-glucopyranoside were synthesized and oxidized to generate 3-methoxy-5-deutero-2-hydro-2-furanol in the former case and 3-trisdeuteromethoxy-2,5-dihydro-2-furanol in the latter case. Oxidation using one molar equivalent of periodate led to preferential formation of hemialdal products and (E)-4-hydroxy-2-methoxy-2-butenal. The latter product was also formed upon end-wise oxidation of methyl 4’-O-methyl-cellobioside, wherein the reducing unit was released as non-oxidized methyl β-d-glucopyranoside. This data indicate that periodate oxidation of cellulosic model substrates might be accompanied by peeling reactions and formation of β-elimination products even under slightly acidic conditions.

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Apixaban is a highly potent, selective, and efficacious inhibitor of blood coagulation factor Xa. A practical and efficient process has been developed for the preparation of the key intermediate of apixaban. Starting from inexpensive 4-chloronitrobenzene and piperidine, an eight-step procedure for the intermediate has been developed. In this case, sodium chlorite is used twice to oxidize the piperidine cycle to the corresponding lactam under a CO₂ atmosphere, resulting in the construction of two lactams. Furthermore, most of these reactions are highly efficient and practical as they occur under mild conditions. Most of the intermediates can be obtained through simple slurry or recrystallization, and column chromatography purification is not necessary.

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This work represents the development of natural kaolinite mineral (Kao)-gold nanoparticles (GNPs) modified screen-printed carbon electrode (SPCE) based on biocompatible electrode material for the electrochemical quantification of propyphenazone and the investigation of the interaction between propyphenazone and ds-DNA. The surface characteristics of the Kao-GNPs/SPCE were examined by cyclic voltammetry, electrochemical impedance spectroscopy, and field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy methods. The effect of Kao and gold compositions, pH, and interferences studied the analytical performance of this sensor. Propyphenazone has an irreversible oxidation signal on the Kao-GNPs/SPCE sensor surface. Based on this oxidation signal, calibration works were carried out using differential pulse voltammetry, and linear working range, LOD, and LOQ were determined. The real sample analysis of propyphenazone was implemented in human serum samples with a recovery value of 99.43%. Binding constant (K) and Gibbs free energy change (ΔG°) relating to the interaction between propyphenazone and ds-DNA were calculated to be 2.14 (± 0.42) × 10⁴ M⁻¹ and − 24.70 kJ mol⁻¹, respectively.

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