Russian Journal of Physical Chemistry B最新文献

Benzene is one of the most common classes of industrial chemicals. As a rule, it enters the atmosphere as a result of man-made accidents and during the evaporation of solvents. Benzene and its derivatives are toxic and have a negative impact on the environment and the human body. Therefore, issues related to the transformation of benzene in the atmosphere are of increased interest. In this study, the structures and electronic energies of equilibrium configurations and transition complexes of the C₆H₆F and C₆H₆F⁺ systems are calculated using the density functional theory. It is shown that the interaction of benzene with atomic fluorine can proceed through two channels: the elimination of hydrogen with the formation of a phenyl radical and the addition of a fluorine atom with the formation of an ipso-fluorocyclohexadienyl radical. It is established that for the dissociation of the ipso-fluorocyclohexadienyl radical into fluorobenzene and atomic hydrogen, it is necessary to expend about 27 kcal/mol. This indicates a low probability of this process occurring at low temperatures. Under experimental conditions, when the temperature of fluorine atoms is about 1000 K, the ipso-fluorocyclohexadienyl radical decomposes to form fluorobenzene. In this case, the occurrence of secondary reactions is unlikely. The conclusions drawn from the analysis of the results of quantum chemical calculations are in close agreement with the experimental data.

The intense precipitation of energetic electrons from the Earth’s radiation belt (ERB) is one of the most important sources of ionization in the ionosphere and atmosphere. A large-scale statistical analysis is carried out of the data from continuous low-orbit satellite observations of solar-cycle variations in the flux enhancements of the ERB electrons with energy >30 keV at an altitude of 850 km, acquired from the NOAA/POES and MetOp satellites in the interval from 1998 to 2022. The basic features of artificial failures in the satellite database with high-time resolution measurements in the interval from 2014 to 2022 are found and described. Appropriate data correction is carried out. It is shown that the average annual number of days with electron flux enhancements increases rapidly within three years after the solar-cycle maximum and reaches its greatest value near the middle of the declining phase of solar activity. Then the frequency of event occurrence begins to decrease noticeably within an 8-year interval, including the minimum, rising, and maximum phases of the solar cycle. The minimum level is achieved at the maximum solar activity.

The kinetics of dissolution and the electrochemical features of the behavior of magnetite (in cathodic polarization) in solutions of sulfuric and orthophosphoric acids are studied. Two independent experimental methods establish that the rate and current of dissolution in H₃PO₄ are higher than in H₂SO₄. This pattern is explained based on the stronger complexing properties of various kinds of phosphate anions in comparison with sulfate anions in solution with iron(III) ions. In the range of studied concentrations of orthophosphoric and sulfuric acids, as well as Fe(II) and Fe(III) ions, the reaction orders for orthophosphoric and sulfuric acids are 1.3 ± 0.1; for iron(II) ions, 0.25 ± 0.1; and for iron(III) ions, –0.25 ± 0.1.

In the interaction of high-molecular ammonium polyphosphate with polyethylene polyamine, thermoplastic polymers with T_g = 46.3–50.7°C, T_soft = 43–92°C, and T_flow = 85–152°C are obtained. Thermal heat resistance, moisture resistance, and the degree of crystallinity depending on the concentration of polyethylene polyamine are measured. The bending strength of polymers and reinforced composites is measured. A chemical scheme for the formation of a polycomplex is proposed and its structure is considered.

This work deals with phytochemical synthesis of TiO₂ nanoparticles by using leaf extract of Ficus benghalensis tree and evaluation of their antibacterial and photocatalytic activities. The synthesized TiO₂ nanoparticles were characterized by using X-ray diffraction, Attenuated total reflectance Infrared, UV visible spectroscopy and transmission electron microscopy as well as scanning electron microscopy techniques. The characterizations revealed formation of stable, spherical nanoparticles of anatase phase of TiO₂ with average diameter of 21 nm. The particles showed excellent antibacterial activity against Bacillus cereus (Gram-positive) and Escherichia coli (Gram-negative) bacteria. The photocatalytic testing showed complete degradation of model pollutants from cationic and anionic dye family namely methylene blue (cationic dye) and methyl orange (anionic dye) that confirmed the excellent photocatalytic activity of the particles.

The pressure of 1,1-diamino-2,2-dinitroethylene (FOX-7) vapors in the temperature range 140–160°C is determined by the manometric method. The correlation dependence of log P_vap on 1/T is established, which makes it possible to estimate the value of P_vap with satisfactory accuracy in the temperature range of 100–200°C. The kinetics of the reaction in the gas phase are measured at temperatures of 200–230°C and m/V = 10^–3–10^–4 g/cm³. It is found that under these conditions, in parallel with the usual monomolecular isomerization reaction into the aci-form, a chain process of the direct oxidation of FOX-7 by NO₂ proceeds. The consequence of this reaction is a significant decrease in the activation energy observed and the appearance of a dependence of the rate on the experimental conditions. The scheme of the main stages of the chain reaction is presented and the conditions necessary for the manifestation of this reaction are determined.

The methods of mathematical modeling are used to explore the initiation of combustion of a large mass of a condensed mixture in the local contact with the end face of the burning layer. It is shown that the minimum width of the igniting layer is proportional to the width of the thermal front of the combustion wave. The coefficient of proportionality is determined by the initial temperature, heat, and activation energy of the reaction. The calculation results can be used to estimate the effective activation energy of the reaction that controls the combustion mechanism of a gasless system.

The effect of the ratio of the reagents on a stabilized cool flame (CF) of rich propane-oxygen mixtures is investigated. It is found that with an increase in the initial concentration of propane in the mixture, its consumption, as well as the concentration of propylene, has a maximum at a ratio of C₃H₈ : O₂ = 1 : 1. In this case, the selectivity of propylene formation reaches a maximum at a ratio of C₃H₈ : O₂ = 4 : 1. It is shown that an increase in the initial propane concentration in the mixture increases the yield of methane, but reduces the yield of propylene, ethylene, hydrogen, CO, CO₂, methanol, formaldehyde and acetaldehyde. At a ratio of C₃H₈ : O₂ = 6 : 1, ethane was also found in the reaction products. The possibility of ethanol formation in the reactions of ethoxyl and hydroxyethyl radicals with acetaldehyde is analyzed using the CBS-QB3 quantum-chemical method.

Currently, modified oxidized (intercalated) graphites (OGs) and thermally expanded graphites (TEGs) obtained from them are used to solve many applied problems. This is due to the fact that while retaining all the properties of layered graphite compounds, split graphite particles have important new properties, such as ease of molding, low bulk density, and active interaction with the polymer matrix. However, the question of the mechanisms of expansion of OG and the properties of TEG particles split into layers has not been sufficiently studied. The establishment of experimental patterns of expansion processes of graphite oxidized by acids contributes to the understanding of the set of stages of complex processes occurring during the expansion of graphite particles in a gas atmosphere and in polymer matrices. The aim of this study is to synthesize a colloidal-graphite (CG) suspension based on TEG particles and determine the properties of suspensions and expansion processes of OG during thermal and microwave heating. As a result of modifying TEG with a low bulk density in the activating media, CG suspensions are synthesized without a vibration grinding stage. The splitting of graphite materials after chemical modification by thermal and microwave-stimulated heating leads to the formation of graphene-like structures. The development of techniques for modifying electrically conductive porous samples of materials used as electrodes makes it possible to introduce nanographite particles under the influence of an electric field.

The reaction rate constant of a chlorine atom with dimethyl sulfide (DMS) is measured in the temperature range 308–366 K by the method of resonant fluorescence (RF) of chlorine atoms. It is shown that the reaction rate constant decreases during experiments at a higher temperature. At a temperature of 308 K, the rate constant of this reaction is measured at different ratios of the reaction time and the diffusion time of chlorine atoms to the reactor wall. The data of these experiments show that with an increase in the diffusion time of the active centers to the surface of the reactor, compared with the contact time of the reagents, a decrease in the measured reaction rate constant is observed. This allows us to assert that the reaction is heterogeneous and the interaction of the chlorine atom with the DMS occurs on the surface of the reactor.