Vol 97, No 5 (2023)

Models of solutions of tert-butyl alcohol (TBA) in carbon tetrachloride (CTC) are obtained via all-atom molecular dynamics modeling. The excess volume of the solution and the apparent and intrinsic (geometric) volumes of both components are calculated throughout the range of concentrations. It is shown that the apparent and intrinsic molar volumes of TBA in the limit of low concentrations in solution are notably larger than in pure alcohol. At the same time, their values fall rapidly in a narrow range of concentrations (from 0 to 0.1 mole fractions), and then move almost linearly to their limit values in alcohol. It is found that such behavior of the volumetric characteristics of TBA is due to the specific association of alcohol at low concentrations because of the hydrogen bonding among TBA molecules.

The mechanisms of hydrolysis of a model iron–sulfur–nitrosyl complex (ISNC) [Fe(NO)2(SCH2)2]+ 1 with thioformaldehyde ligands have been studied using the density functional theory and polarizable continuum model of water. Quantum chemical calculations employed the TPSSH and M06 functionals and def2-TZVP basis set and took into account interactions with water medium. Hydrolysis of 1 was found to be an exothermic process with small activation energy whereas exchange of NO for H2O is thermodynamically unfavorable. The calculations have predicted lower activation barrier for the associative mechanism with concerted replacement of SCH2 by H2O than for dissociative mechanism with homolytic bond cleavage of the Fe–S coordination bond in water. The mechanism of hydrolysis that involves participation of OH– was found to be less probable at pH 7. The calculation results show that ISNC 1 is of {Fe1+(NO•)2}9 type and retains its tetrahedral structure that is typical for crystals of ISNC with thiocarbonyl ligands.

The review presents an attempt to collect and systematize the available data on the antioxidant activity of glycyrrhizin obtained by various physicochemical methods and to stimulate further discussions on the mechanisms of its activity and prospects for its use as a multifunctional drug delivery system.

A study is performed of the photophysical properties of indolo[3,2-b]carbazole-based compounds synthesized earlier. The charge carrier mobility in the space charge-limited current mode and the energy levels of the highest occupied and lowest unoccupied molecular orbitals in the compounds are determined. It is shown that indolo[3,2-b]carbazole derivatives can be used as hole transporting layers in organic light-emitting diodes.

The structure of the sonoluminescence spectra of argon-saturated aqueous solutions of CaCl2 and NaCl of various concentrations is considered in detail. The frequency of ultrasound is 20 kHz, and the output power is 18 W. The spectrum of the CaCl2 solution changes considerably as the concentration rises. The intensity of the continuum passes through a maximum near the saturation concentration. Atomic, ionic, and molecular metal lines are observed for medium concentration values and disappear at high concentrations. Similar behavior is displayed by the spectra of NaCl solutions. The differences between the spectra are explained by the change in the vapor–gas content of the bubbles and the nature of their population, from large and non-inertial to small and pulsating inertially.

Self-diffusion coefficients (SDCs) of 3-amino-1-propanol (3AP), monoethanolamine (MEA), and water molecules are measured via 1H NMR using a pulsed magnetic field gradient and a stimulated echo sequence throughout a range of concentrations at temperatures of 293–333 K. It is found that the studied amino alcohols and water form a nearly tetrahedral three-dimensional network of hydrogen bonds between the molecules of the system. It is shown that this network is stable in the liquid phase, despite the mobility of the molecules that constitute the network. The mechanism of molecular mobility is studied. It is shown that the SDC of the molecules of the above amino alcohols and their aqueous solutions depends linearly on temperature. It is concluded that the molecular mobility mechanism has a pattern of activation. To verify this hypothesis and interpret the mechanism, the energies of activation are calculated for the self-diffusion of all the studied molecules in water–amino alcohol systems. The determined energies of activation for the mobility of amino alcohol molecules in aqueous systems have similar values, suggesting they undergo interactions that produce either mixed water–amino alcohol spatial networks or amino alcohol–water molecule associations in the liquid phase.

The η-carbide Nb3(Fe,Al)3C phase was synthesized for the first time by mechanical alloying of Nb, Al, and Fe in petroleum ether followed by annealing. The synthesis of carbide occurs due to carbon accumulated from the grinding medium. If mechanical alloying is performed using steel vials and balls, the composites based on η-carbide can be obtained without additional introduction of iron; contaminant iron is involved in the formation of Nb3(Fe,Al)3C.

The behavior of the isotherm and molecular distributions inside the binodal is analyzed to solving an Ising model obtained on the basis of cluster variation for planar lattices with coordination numbers 3, 4, 6. It is found that the microscopic approach gives a probabilistic interpretation of the Maxwell macroscopic rule and explains how the isotherm a secant appears between the regions of coexistence of two phases. A region of no solutions (the region of degeneracy) is found inside the binodal, and the critical temperatures of degeneracy at which the nontrivial solution to the equations disappears are calculated for this region. The region of degeneracy inside the binodal expands and approaches the binodal curve as the temperature falls, so the degeneracy curve and the binodal become indistinguishable. Numerical iterative calculations are used to study the dependence of the region of no solution inside the binodal as a cluster grows. The critical temperature of degeneracy asymptotically approaches that of the binodal as the cluster grows. Existing ways of interpreting metastable states are discussed, along with as the correspondence between the new results and previously known mean-field (ignoring correlations) and quasi-chemical (considering only direct correlations) approximations, and an exact result of the Yang–Lee condensation theory.

Single-phase ceramic samples with new compositions (1 – x – у)(Na0.5Bi0.5)TiO3–хBaTiO3–у(K0.5Na0.5)NbO3 (x = 0.05, у = 0–0.15) modified with ZnO and GeO2 additions were obtained by solid-phase synthesis. Their crystal structure, microstructure, and dielectric and local piezoelectric properties were studied. A phase with a perovskite structure with a pseudocubic unit cell was found to form in all of the synthesized samples; it was shown that the unit cell volume increased as a result of the partial replacement of base cations by complex additive cations. The ferroelectric phase transitions were confirmed by dielectric spectroscopy. Residual piezoelectric hysteresis loops were obtained for the synthesized samples in the polarization switching spectroscopy mode, which confirmed the switching of ferroelectric polarization.

Characterizing the dependence of the retention indices (RIs) of sorbates of different chemical origins on the content (С) of organic solvents (methanol, acetonitrile) in eluents used in reversed-phase HPLC shows that the coefficients dRI/dC of the same compounds for eluents of different compositions differ considerably. The range of variations in coefficients dRI/dC for water–methanol eluents (–5.6 to +4.6) is approximately twice that of water–acetonitrile eluents (−4.5 to +0.8). It is also found that for nonpolar compounds when using water–acetonitrile eluents, the dRI/dC values are typically lower than those for water–methanol eluents. The opposite is observed for polar compounds. The signs and absolute values of coefficients dRI/dC are largely determined by the polarity of the sorbates. dRI/dC > 0 for nonpolar sorbates, and dRI/dC < 0 for sorbates of higher polarity. Determination even of the sign of this coefficient therefore provides important information about the chemical nature of sorbates. It is shown that coefficients dRI/dC do not correlate with either the RI values or hydrophobicity logPlog⁡. However, they do correlate with homologous increments of hydrophobicity ilogP and the homologous increments of RI iRI for eluents of any composition. Quantities ilogP and iRI characterize the polarity of homologous series of sorbates, rather than the polarity of the particular sorbates.

The authors study the corrosion of low-carbon steel in solutions of H2SO4 containing Fe2(SO4)3 with and without additives of individual and mixed corrosion inhibitors. It is established that the oxidizing capacity of the given system (in which the reactions between iron, an acid solution, and Fe(III) salts are thermodynamically allowed), characterized by the redox potential of an Fe(III)/Fe(II) pair, is largely determined by its anionic composition: sulfate anions of a corrosive medium bind Fe(III) cations into complex compounds, reducing their oxidizing ability. Partial reactions of the anodic ionization of iron and the cathodic reduction of H+ and Fe(III) cations are revealed in analyzing the effect convection of the medium has on the electrode reactions of low-carbon steel. The first two reactions are characterized by kinetic control; the third, by diffusion. It is shown that the accelerating effect Fe2(SO4)3 has on the corrosion of steel in a solution with H2SO4 is mainly due to the reduction of Fe(III). In contrast, the accelerating action of Fe(III) cations affects all partial reactions of steel in an inhibited acid. There is a large drop in the apparent coefficient of diffusion of Fe(III) cations (DFe(III)) in inhibited solutions, relative to an uninhibited medium. Data on the corrosion of low-carbon steel in the given media, obtained from the mass loss of metal samples, are in full agreement with results from studying partial electrode reactions. Consideration is given to the accelerating effect Fe2(SO4)3 has on the corrosion of steel in solutions of H2SO4 with and without inhibitors. In these environments, the corrosion of steel is determined by the convective factor, which is typical of processes with diffusion control. The empirical dependence of the rate of steel corrosion on the intensity of the medium’s flow is described by linear dependence k = kst + λw1/2, where kst is the rate of the corrosion of steel in a static environment, w is the rotational speed of the propeller agitator creating the flow of the medium, and λ is an empirical coefficient.

The developed kinetics of the vibrationally excited states of ozone (with excitation of up to five vibrational quanta), built into the chemical kinetics of O/N/Ar mixtures, was used to model the series of photolysis experiments of V.N. Azyazov et al. The experimental and calculated dynamics of O3 and O2(a1∆) in various O3/O2/Ar mixtures were compared. The dynamics of chemiluminescent radiation of NO∗2NO2∗ in the titration technique and the applicability of this technique to measuring the dynamics of O atoms in an O3/O2/N2O/Ar mixture were considered. The dynamics of various states of O3(v1,v2,v3) after ozone photolysis was analyzed in detail. The role of these states in the acceleration of the chemical conversion of oxygen components and nitrogen oxides, occurring with competition with ozone vibrational relaxation, was considered.