Vol 97, No 2 (2023)

Potentiometry is used to study the formation of Cu(II)–1-phenyl-2,3-dimethylpyrazoline-5-thione (1-P-2,3-DMP-5-T) complex in a mixed solvent. The compositions of the complexes are determined, and their stepwise constants of stability are calculated. It is shown that when Cu(II) reacts with 1-P-2,3-DMP-5-T in a medium of mixed solvent HCl + acetone (10 : 1), quantities ΔH, ΔG, and ΔS have negative values at all stages.

An algorithm is described for calculating the equilibrium constants and changes in the enthalpy of chemical reactions according to data from a calorimetric experiment performed on instruments of different types. Freeware is developed that executes the described algorithm. Differences from existing computer programs with similar functionality are briefly discussed, along with different statistical criteria of maximum likelihood.

A study is performed of the kinetics of oxidation of lead babbitt with 1.0 wt % of sodium in the 373–473 K range of temperatures. The kinetic and energy parameters of the oxidation of the alloys are determined. It is found that the weight gain of the alloys grows rapidly during the first 15–20 min of oxidation and then acquires an almost constant value. Oxide films that form at the beginning of oxidation have no protective properties, as is confirmed by an increase in the alloys’ rate of oxidation along with temperature in the initial period. It is revealed that sodium dopant additives taken in concentrations of 0.01–1.0 wt % enhance the oxidizability of the original alloy and considerably refine its microstructure. X-ray diffraction analysis shows that the alloys’ products of oxidation consist of oxides (Pb3Sb2O8.47)6.4, PbO, Pb3O4, Pb0.828O2, Sb2O4, Na3SbO3, NaSbO3, and PbSb2O6.

Intense signals of [M–H]– ions have been detected in the low-energy region of the resonance electron capture mass spectra of xanthine and its methyl derivatives. It was assumed that xanthine molecules can act as radioprotectors in living cells. It was concluded that the discovered release of the carbonyl and methyl groups is associated with xanthine metabolism reactions in the tissues of living organisms.

The boundaries of the segregation region in sulfuric (nitric, chloric, hydrochloric) acid–potassium bis(alkylpolyoxyethylene) phosphate–water systems at 25°С have been determined by isothermal titration. The salting-out ability of the inorganic acid was found to increase with a decrease in the absolute value of the Gibbs energy of anion hydration. Based on the obtained diagrams, the optimum parameters of extraction were determined, and tendencies in the distribution of some metal ions in the sulfuric acid–potassium bis(alkylpolyoxyethylene) phosphate–water system were studied. Conditions for quantitative extraction of thallium(III) in the presence of alkali metal halides were found.

An expression is obtained for an effective geometric potential based on a coordinate system for a nanoribbon twisted in the form of a helicoid. The effective geometric potential for a Schrödinger equation is used to study a graphene nanoribbon of finite length with “armchair” edges under the action of an external electric field parallel to them. Solutions are calculated for the energy levels and wave functions of electrons in the vicinity of the Dirac point. It is shown there is only one state in the transverse direction.

A study is performed of the effect the way of standardizing the molecular structure and parameters of calculating molecular fingerprints has on the accuracy of predicting constants of acidity. It is shown that standardization (i.e., the choice of the tautomeric form and the way of writing the structure of the molecule) using OpenEye QuacPac gives the best results, but the RDKit library allows comparable accuracy to be achieved. It is established that how the charge state is chosen has a great effect on the accuracy of predictions. The accuracy of predictions depending on the radius (size of substructures) of circular molecular fingerprints is studied, and the best results are achieved using radius r = 2. A random forest, a machine learning algorithm, is used. It is also shown that the use of support vectors ensures fairly high accuracy when optimizing hyperparameters.

A set of physicochemical means is used to study the adsorption properties of surfaces of silicas based on Silochrome C-120 with surface-grafted groups of acetoacetic ester saturated with transition metal ions. Gas chromatography is used to study the effect nickel, cobalt, and copper ethylacetoacetates have on the thermodynamic characteristics of adsorption (TCA) of different classes of organic substances on SiO2. Experimental data on the retention of adsorbates with different donor-acceptor properties (n-alkanes and chloroalkanes, alkenes, aromatic and oxygen-containing substances) are used to calculate differential molar heats of adsorption q¯dif,1 the change in the standard differential molar entropy ΔS¯S1,C and deposits Δq¯dif,1(spec) in the energy of dispersion and specific interactions.

The possibility is considered of obtaining superhydrophobic (SHP) protective films on surfaces of aluminum alloy D16. It is shown that laser treatment of the alloy and its subsequent modification in solutions of carboxylic and phosphonic acids results in superhydrophobization of its surface. The protective ability of the SHP coatings is determined from polarization measurements and corrosion tests in a salt spray chamber and an urban atmosphere. Electrochemical testing of samples of D16 alloy in a sodium chloride solution shows that SHP films effectively prevent its local depassivation. It is established that SHP films formed from solutions of octadecylphosphonic and stearic acids effectively prevent alloy corrosion under atmospheric conditions.

The mechanisms of retention and separation of the enantiomers of chiral oxazolopyrroloquinolones on a stationary phase with graftеd macrocyclic antibiotic ristocetin A under conditions of high-performance liquid chromatography with aqueous methanol mobile phases have been studied. The retention factor was found to decrease monotonically when the CH3OH concentration in the mobile phase increased to 90 vol %; then it slightly increased as the composition of the mobile phase approached pure methanol. The thermodynamics of adsorption of oxazolopyrroloquinolones in different regions of this dependence was studied. A mathematical model has been proposed; it describes well the experimental data and allows for analyte solvation in the mobile phase and competitive adsorption (with mobile phase components) on a chiral selector. The results were compared with previously obtained data for water–acetonitrile mobile phases. The reasons for the observed differences were discussed.