Theoretical and Experimental Chemistry最新文献

The kinetics of the liquid-phase oxidation of cumene (RH) with molecular oxygen in the presence of KMnO₄ and N-hydroxysuccinimide (NHSI) is studied. An increase in the reaction rate when adding acetic acid is established. An synergistic effect of KMnO₄ and NHSI in aerobic oxidation of RH is found. This can be associated with the formation of C-centered (R^⦁) and O-centered (SINO^⦁) radicals that participate in the chain initiation stage and the catalysis of the chain propagation stage by the SINO^⦁ radical.

Organic electrolytes based on different solvents (propylene carbonate, γ-butyrolactone, sulfolane, and benzonitrile) with high boiling points have been studied in supercapacitors. The cyclic voltammetry data, dependence of capacitance, internal resistance on voltage, and endurance tests indicate that a solution of spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP-BF4) in benzonitrile is one of the most reliable electrolytes in a voltage range of about 2.5 V up to temperature of 100-110°C . The high electrochemical stability of benzonitrile under such harsh conditions can be explained by the absence of an SEI film formation process on the electrode surface that doesn’t cause a noticeable internal resistance increase and capacity decrease when voltage is increased.

The current state of research on spin-orbit interaction in cofactor-free oxidases and dioxygenases during oxygen activation is considered. The spin activation of triplet oxygen during combustion and respiration is analyzed in comparison with the reactions of flavin-containing enzymes, as well as important cofactor-independent dioxygenases. The mechanism of the triplet-singlet transition in glucose oxidase and a number of dioxygenases, including the RuBisCo oxygenase pathway and chirality-induced spin selectivity, is considered.

Electrochemical properties of composites based on metals, metal oxides, and carbon nanotubes and nanofibers in the reaction of oxygen reduction in oxygen (air) electrodes of fuel cells, the reaction of hydrogen oxidation in hydrogen electrodes of fuel cells, and the reaction of electrochemical storage of hydrogen in a hydride electrode of a nickel-metal hydride battery are considered It is shown that new composites with high electrocatalytic characteristics can be created by changing a route of electrochemical reactions from a catalyst to a support. Prospects of an electrochemical method for the synthesis of graphene oxide, graphene, and partially unzipped carbon nanotubes are discussed. Nanocomposites of carbon nitride and partially unzipped carbon nanotubes are considered as promising materials for a metal-free catalyst of oxygen electrodes.

It is shown that interaction of electron donor tioconazole (TCZ) with π acceptors chloroanilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, and picric acid leads to formation of the charge transfer complexes. The obtained complexes are characterized by spectral methods, and specific features of their structure are revealed by DFT. It is found that such complexes possess cytotoxic activity against breast cancer line (MCF-7), and their efficiency on IC₅₀ criterion exceeds the efficiency of the individual TCZ.

Mechanochemical (MCT) and ultrasonic (UST) treatments have been used to change the particle sizes of photoactive oxides ZnO and TiO₂ and their mixtures with inert oxides (MgO, Al₂O₃, and SiO₂). It is shown that MCT leads to a significant decrease in the size of particles, while UST either does not affect their size or leads to an insignificant increase in their size due to aggregation. It is established that a decrease in particle size is accompanied by an increase in the band gap. The dilution of photoactive oxides decreases the metronidazole oxidative destruction rate constant. The reaction rate constant, which refers to a unit mass of a photoactive oxide, and metronidazole conversion decrease for all samples when the size of photoactive oxide particles is decreased (in the range of 20-50 nm).

The thermodynamic and kinetic aspects of vapor-phase carbonylation of methanol are considered, in particular the effect of temperature on the equilibrium yield of products and probable routes of acetyls production. The influence of the catalyst composition on the course of the target process, the influence of hydrogen as a gas promoter on the selectivity/yield of acetyls, the peculiarities of the course of the tandem process (coupling of decomposition and carbonylation of methanol) are analyzed.

Nanocomposites based on crystalline carbon nitride (CGCN) and cobalt titanate (CoTiO₃) have been synthesized and characterized by a number of physico-chemical methods (electron microscopy, electron and IR spectrophotometry, luminescence spectroscopy, and X-ray diffraction). It is concluded based on the analysis of the obtained results, in particular, the luminescence characteristics and Mott–Schottky dependences, that the S-scheme of separation of photogenerated charges between components is realized during the formation of CGCN/CoTiO₃ composites. This leads to a decrease in the recombination of electron–hole pairs and an increase in the efficiency of hydrogen evolution from water–ethanol solutions when compared to the presence of CGCN. The effective quantum yield of hydrogen formation is ~90% under light irradiation at λ = 405 nm with the participation of the composite of the optimal composition.

The features of the synthesis and the structure formation of homogenous phases of Mg(II),Fe(III)-layered double hydroxides with different Mg/Fe ratio in the reaction mixtures have been investigated. The effect of synthesis conditions of the materials, arrangement and molar ratio of the cations in a brucite-like layer, and polytypes of crystalline structure on the sorption properties toward ibuprofen has been studied. The sorption isotherms of ibuprofen on the synthesized sorbents at pH₀ = 7,0 are satisfyingly fitted by the Langmuir model. The influence of the Mg²⁺/Fe³⁺ molar ratio and, respectively, the dimensions of the interlayer space on the maximum adsorption capacities toward ibuprofen in the aqueous solution is not observed. These results can be explained by the interaction of the adsorbate with the surface hydroxyl groups of brucite-like layers, as well as complexing reactions with structure-forming cations of the obtained sorbents.

Zirconium dioxide samples with different crystallinity and phase compositions have been obtained by calcination of a mixture of zirconium oxychloride and sodium bicarbonate at temperatures ranging from 150 to 800°C. It is established that amorphous ZrO₂ with an zirconium oxycarbonate admixture is formed at 150-200°C. A sample obtained at 400°C contains 50% of the tetragonal phase and 50% of the amorphous ZrO₂ phase, while a mixture of tetragonal and monoclinic phases is formed at 600°C and 800°C (83% of t-ZrO₂/17% m-ZrO₂ and 27% of t-ZrO₂/73% m-ZrO₂, respectively). It is shown that zirconium dioxide obtained at 150°C has the highest efficiency of adsorptive removal of phosphate anions from an water solution as compared with other studied samples.