Vol 66, No 4 (2017)

Literature data on the surface modification of ultra-high-molecular-weight polyethylene as fibers and powder under the influence of low-temperature plasma are analyzed. The change in polymer chemical composition and structure is described. The results of the studies, indicating a significant improvement in the contact and adhesion characteristics of the modified polymer and composite materials, are discussed.

The review analyzes the effects of the reaction conditions on the direction of the reactions between furans/formylfurans and hydrogen peroxide. The revealed dependences serve for the synthesis of the desired products and for development of new methods to access α-hydroxy hydroperoxides of furan aldehydes, 2-furanoic acid and its esters and amides, a series of furoic acids bearing the substituent at the furan ring, 2(5H)-furanone and its homologs and functional derivatives, as well as 2,5-dialkoxydihydrofurans. The developed procedures are more advantageous than the conventional methods.

We compared two approaches to the mathematical modeling of state population dynamics in a model reaction complex, which is intended for the description of an intramolecular photochemical reaction in a four-level molecule or a secondary photochemical reaction caused by an irreversible transfer of photoexcitation energy from a three-level reagent molecule to one of the states of the product molecule. One approach (used in theoretical photochemistry) involves using the solution of the optical Bloch equations for the complex, while another (used in theoretical spectroscopy) involves the solution of the Schrцdinger equation for a composite system of complex molecules, quantized radiation field, and environment phonon field. The results of these approaches are in agreement in the case of irradiation of the model complex with ultrashort pulses with a resonant carrier frequency, but are considerably different in the case of irradiation with a long pulse. We conclude that when modeling the photoreaction dynamics using a long radiation pulse, the approach based on theoretical spectroscopy formalism should be used. For the considered reactions, the obtained characteristics of the dynamics can serve as a reference point for the choice of photoreaction, the study of which by photochemistry methods will make possible the confirmation of the accuracy of the drawn conclusion and the used concepts on the transformation of light by molecules, accompanied by a photoreaction.

Porous films formed by cylindrical geometrically anisotropic fragments of TiO₂ have been produced by electrochemical anodization of titanium. The specific surface area and pore volume of the samples were determined by the BET method. It is shown that the samples have a bimodal pore-size distribution with maxima depending on the anodization voltage: by increase in voltage the inner diameter of the cylindrical pores grows, which leads to a decrease in the specific surface area. Dye sensitized solar cells were assembled on the basis of the obtained materials to study the effect of certain characteristics on the efficiency of solar energy conversion. The electrical transport properties of the films were studied by impedance spectroscopy.

The solution state and thermodynamic stability of complexes of the new antituberculosis agent 1,4-bis(amidomethylsulfinyl)butane (L) with iron(III), copper(II), cobalt(II), nickel(II), and manganese(II) in an aqueous solution in the presence and in the absence of the nonionic surfactant Brij 35 were studied by spectrophotometry, pH potentiometry, NMR relaxation technique (T = 25 °C; variable ionic strength), and mathematical simulation. The geometry optimization of all structures was carried out by the molecular mechanics method MM2 in order to obtain data on coordination modes. In addition, the structure of 1,4-bis(amidomethylsulfinyl)butane was refined by the DFT/B3LYP/6-311++G(d,p) quantum chemical method using the IEFPCM model to take into account solvent effects. In an aqueous solution (in the concentration range of 1.3•10^–5—1•10^–3 mol L–1) and in the presence of Brij 35, 1,4-bis(amidomethylsulfinyl)butane exists as a neutral monomer. The Beer—Lambert—Bouguer law is obeyed in a wide concentration range for compound L in an aqueous solution, as well as in the presence of the surfactant, which can be used for the quantification of compound L. Iron(III), cobalt(II), and nickel(II) were shown to form 1: 1 mononuclear complexes with L; and copper(II) forms, 1: 1 and 2: 2 complexes. The presence of Brij 35 in the Cu²⁺—L system at a micellar concentration promotes the formation of a dinuclear complex.

Using IR Fourier transform spectroscopy we consider biosynthetic lignin models, namely, dehydropolymers. Quantum chemical calculations of IR spectra of model lignin structures were carried out within the framework of the density functional theory with the B3LYP functional in the 6-31+G(d,p) basis. The IR spectrum of a dimer with the C(8)—O—C(4) fragment describes well the specific features of the spectrum of the dehydropolymer synthesized from coniferyl alcohol. The presence of dimeric structures with double bonds in aliphatic chains and ether bonds between aromatic rings was determined in dehydropolymers from ferulic acid. The results of theoretical and experimental studies were shown to be in agreement with each other.

The effect of the reduction procedure of graphite oxide (GO) on activity of platinum supported catalysts in liquid-phase hydrogenation of nitrobenzene and dec-1-ene was studied. The following methods were applied to prepare the catalysts: simultaneous reduction of graphite oxide and H₂PtCl₆; deposition of platinum on graphite oxide which was preliminary subjected to reduction with sodium tetrahydroborate or hydrazine hydrate, or to thermal reduction at 1000 and 1050 °С. It was shown that at equal Pt particles size of ca. 2 nm the catalyst supported on thermally reduced graphite oxide is more active in the model reactions than the catalysts supported on chemically reduced graphite oxide. The catalyst prepared by simultaneous reduction was the least active.

Layered hydroxides with a molar ratio of metals Mg: Al: M = 3: 1: 1 (M = Fe, Ce, Zr, Cr) were prepared and served as a basis to obtain the mixed oxides MgAlO_x, MgAlCrO_x, MgAlCeO_x, MgAlZrO_x, and MgAlCrO_x. Powder X-ray diffraction was used to study the phase composition of the oxides. It was suggested that the catalyst active surface is related to the presence of spineltype X-ray amorphous compounds. Ammonia adsorption was used to determine the total acidity, and deuterated acetonitrile adsorption was applied to estimate the strength of acid sites. The catalytic properties of complex oxides were studied in the ethanol condensation reaction. An attempt was made to correlate the catalyst activity and selectivity and the distribution of acid and base sites on the catalyst surface.

The technique of synthesis of 2,3,5-trimethyl-1,4-benzoquinon via catalytic oxidation of 2,3,6-trimethylphenol in H₂O₂—H₂O—PhCH₃ system with vibrational stirring is developed. Xerogels TiO₂ and TiO₂—SiO₂ were used as catalysts in the process. The effect of physicochemical properties of xerogels on the course and characteristics of oxidation is studied.

Hydrochloric acid reacts with 5-ethyl-2-methallylsulfanyl-6-methylpyrimidin-4(3H)-ones to protonate the nitrogen atom; it adds to the double bond of 2-prenylsulfanyl-6-(trifluoromethyl)pyrimidin-4(3H)-one and gives the addition and heterocyclization products in the case of 2-prenylsulfanyl-6-methylpyrimidin-4(3H)-one.

Method of radiation polymerization of N-vinylpirrolidone (NVP) in the presence of fullerene C₆₀ has been used to obtain water soluble compound containing fullerene C₆₀. The yield of resulted product was ~10% in the case of low-temperature radiation polymerization of NVP—C₆₀ mixture in ethanol and ~40% at 300 K. The content of C₆₀ in obtained product was ~0.5 wt.%.

The results of a comparative study of the rheological properties of acrylonitrile copolymers solutions synthesized by classical and controlled radical polymerizations in aprotic solvents (dimethyl sulfoxide, dimethylformamide, and dimethylacetamide) are presented. The influence of the chemical nature of comonomers (styrene and acrylamide) and their share in the composition of the chain on the viscosity of solutions is discussed. For all copolymers, the viscosity of solutions is determined by a product of the intrinsic viscosity per concentration. In the transition from dilute and semi-dilute solutions to the concentrated solutions, the form of the dependence changes from linear to power-law. The concentrated solutions are non-Newtonian liquids exhibiting viscoelasticity. Copolymer solutions obtained by controlled radical polymerization have a higher viscosity and less pronounced non-Newtonian behavior. The solutions of copolymers with a high comonomer content obtained in dimethylformamide have the lowest viscosity.

Quantum chemical calculations of arylation reactions of ferrocene with three aminobenzoic acid isomers were carried out. Based on the results of the calculations using HF/3-21G, DFT/ B3LYP/3-21G and their comparison with experimentally obtained data, the causes of the difference in the yields of isomer reaction products in the gas phase and in a solution were analyzed.

Ethyl 3-tert-butyl-4-oxo-7-X-4,6-dihydropyrazolo[5,1-c][1,2,4]triazine-8-carboxylates (X = H, Cl, Br) were synthesized for the first time by diazotization of 7-amino-3-tert-butyl-4oxo-8-ethoxycarbonyl-6H-pyrazolo[5,1-c][1,2,4]triazines with tert-butyl nitrite in the presence of trimethylsilyl halides. A new method was developed: a reaction between 7-amino-3-tert-butyl-4-oxo-6H-pyrazolo[5,1-c][1,2,4]triazine-8-carboxylic acid and I₂/TEA followed by treatment with NaBH₄ led to a mild decarboxylation. The acid reacts with N-halosuccinimides to give novel 8-halo-substituted derivatives. The amino groups of the latter were acylated by treatment with trifluoroacetic anhydride to give monoacylation products.