Volume 67, Nº 6 (2018)
- Ano: 2018
- Artigos: 31
- URL: https://journals.rcsi.science/1066-5285/issue/view/15001
Reviews
Mechanochemical processes with the reaction-induced mechanical activation. Chemo-mechanochemical effect
Resumo
The review addresses the special case of mechanical activation of solid-state chemical reactions when the stress field, strain, and defects in crystals are induced by the chemical reaction itself rather than by the external mechanical impact (chemo-mechanochemical (CMC) effect). This review presents the analysis and state-of-the-art of research activities in this area. Different cases of the CMC effect in homogeneous and heterogeneous systems are considered: with or without changes in the chemical composition, with or without formation of solid products, etc.
Metal sols in ionic liquids: synthesis, properties, and application
Resumo
This review contains the analysis of the state-of-the-art data on synthesis, structure, and practical application of metal sols in ionic liquids. Problems related to stabilization of metallic nanoparticles by the components of ionic liquids are analyzed in detail. Information on catalytic properties of metal sols in ionic liquids is generalized. Examples illustrating practical application of these systems in diverse areas of science and technology are presented.
Full Articles
Radiation-chemical processes leading to origination and accumulation of oxygen in the Earth’s atmosphere
Resumo
The role of natural radioactivity in the formation of the oxygen atmosphere of the Earth is discussed. The origination of oxygen in the free state in the hydrosphere and atmosphere is associated with the radiolysis of the water of the World ocean under the irradiation of radio active isotopes 40K, 235U, 238U, and 232Th. The calculations showed that within the last 3.8 billion years the total weight of oxygen, which could be formed due to this process, is about 7.4•1017 kg, i.е., the value of the same order as the oxygen content in the modern atmosphere of the Earth. The Ocean was an intermediate collector and provided the nucleation of new forms of biological life with oxygen respiration. The consecutive transformation of the Earth’s atmosphere with a gradual increase in the oxygen content became the result of photosynthesis in algae and green plants and thus opened a way to the origination of complicated forms of the life.
The necessary and sufficient conditions for chemical equilibrium
Resumo
The article concerns a widely accepted but incorrect concept of conditions for chemical equilibrium. The authors present a mathematically rigorous derivation of the necessary and sufficient conditions for chemical equilibrium of systems of arbitrary complexity.
DFT study of Raman scattering spectra of complexes of spiropyrans with the silver cluster
Resumo
The computational simulation of structure, energy and spectral characteristics of spiropyrans and their complexes with the cluster containing ten silver atoms was carried out using the density functional theory method (B3LYP/6-31G(d,p)/SDD). A competitive coordination of oxygen-containing substituents in the indoline and benzopyran moieties in spirocyclic molecules to the metal atoms was studied and an effect of position of donor groups on the activity of CO vibrational bands was established in the calculated Raman spectra. We revealed compounds, whose trans-trans-trans isomers upon a complexation with the silver cluster are characterized by the more than 100 times enhanced activity of band associated with the valence vibrations of CO bond in the Raman spectrum.
Thermodynamic modeling of the deposition of Si—C—N films from the gas phase during the decomposition of organosilicon compounds
Resumo
Thermodynamic modeling of the process of chemical vapor deposition (CVD) of SiCx and SiCxNy films from the gas phase was carried out using organosilicon compounds (EtN(SiMe3)2, PhN(SiMe3)2, and PhSiMe3) at reactor pressures of 0.01 and 10 Torr in the temperature range of 500–1200 K. It was established that regions of existence of two phase complexes, namely, SiC + Si3N4 + C and SiC + C, were present on the CVD diagrams calculated for the EtN(SiMe3)2—He and PhN(SiMe3)2—He systems. The CVD diagrams calculated for the EtN(SiMe3)2—NH3, PhN(SiMe3)2—NH3, and PhSiMe3—NH3 systems have regions of existence of three phase complexes, namely, Si3N4 + C, SiC + Si3N4 + C, and SiC + C. The composition of the obtained silicon-containing films was calculated.
Fabrication and physicochemical characterization of graphene oxide derived from thermally expanded graphite
Resumo
Graphene oxide was obtained from expanded graphite according to the modified Hummers method. The reaction time was significantly reduced (from 24 to 8 h) by applying the expanded graphite in the oxidation process. The interlayer distance in obtained samples was equal to 0.70–0.74 nm. Structural features of the material were studied by the powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, XPS spectroscopy, and NMR spectroscopy.
Description of heterogeneity of the sorbent surface on the basis of adsorption kinetic data
Resumo
The kinetics of adsorption of Rb+ and Cs+ ions on different non-polarized and polarized active carbons at temperatures of 25, 35, 45, and 65 °C was investigated. The obtained results were processed using the equations of the pseudo-first- and pseudo-second-order models. The pseudo-second-order model better describes the adsorption of alkaline metal ions on the carbons studied. The kinetic dependences of three types reflecting heterogeneity of the sorbent surface were revealed on the basis of the theoretical analysis of sorption systems.
Preparation and investigation of active carbons based on furfural copolymer
Resumo
Active carbons were synthesized from a furfural copolymer using a polyester resin as an activator. The influence of the temperature of the thermal treatment of the carbon sorbents on the weights and ash contents of the obtained materials was established. The molecular structures of the carbons were studied by NMR spectroscopy.
Structure of sp2-carbon fiber prepared by high-temperature thermomechanical treatment of polyacrylonitrile fiber: a Raman and X-ray diffraction study
Resumo
Structural regularities of the transformation of PAN fibers into high-strength sp2-carbon fiber by high-temperature thermomechanical treatment were established using Raman spectroscopy and X-ray diffraction. Radial heterogeneity of the fiber structure was revealed and quantitatively characterized by Raman micro-mapping.
Regulation of the sizes of silver nanoparticles stabilized with a maleic acid copolymer and the prospect of their biotechnological use
Resumo
Methods of synthesizing silver nanoparticles (SNP) of various sizes stabilized with a maleic acid copolymer are proposed. The colloidal solutions of SNP are characterized by electron spectroscopy, static and dynamic light scattering, transmission electron microscopy. The stability of the obtained SNP in solutions of hydrogen peroxide and a hydrochloric acid salt is studied, their efficiency in antimicrobial activity tests is assessed.
Nanostructured Ni—Cd powders
Resumo
Nanostructured powders of the Ni—Cd system containing 0–50 mol.% Cd obtained by co-reduction of metal salts from aqueous solutions by hydrazine were studied by X-ray diffraction, optical emission spectroscopy and electron microscopy. The reduction leads to formation of polycrystalline particles of 100–350 nm size, consisting of 10–20 nm crystallites. Phase composition of the powders is substantially different from that predicted by equilibrium on the phase diagram. Instead of a two-phase area consisting of Ni—NiCd intermetallide, other phase states are observed. If the system contains up to 6% Cd, the XRD data indicates the presence of a single-phase solid solution with a face centred cubic (fcc)-structure. The increase in the Cd content to ~40% is accompanied by formation of the NiCd5 intermetallide phase, along with a solid solution. In the 40–50% Cd content range, the main phases are NiCd5, as well as a fcc-phase containing up to 18% Cd and characterized by a strong broadening of the diffraction maxima caused by the presence of 2–3 nm crystallites. Furthermore, the system of such composition contains a previously unknown non-stoichiometric phase based on Ni3Cd, having a similar to Cu3Au structure. The results serve to clarify compositions of reduction products and the character of the structural-phase transformations of the intermediate hydroxides and metal products during the reduction process. Based on the obtained data, we proposed a formation scheme for the phases that are unconventional for the studied composition region of the Ni-Cd system. It has been concluded that the main factors determining formation of the reduction products are particle nanoscale dimensionality and occurrence of the reduction process far from equilibrium.
Decay of H2O2 under the action of the colloidal catalyst based on iron(III) oxides in a neutral medium
Resumo
The catalytic activity of the colloidal catalyst based on iron(III) hydroxide was studied in the decomposition of H2O2 in a neutral medium (pH 6.7). A colloidal micellar solution of iron(III) hydroxide after preparation was kept at 19–20 °С for 2 or 20 h without additives or with C2H5OH additives. The decomposition of H2O2 under the action of the colloidal catalyst (20 h) proceeds via the first-order reaction with the decay rate constant kd = 1.26•10–4 s–1, whereas the decay rate of the first-order reaction is kd = 0.77•10–4 s–1 for the colloidal catalyst (2 h) prepared in the presence of C2H5OH.
Oxidative dehydrogenation of ethane to ethylene with carbon dioxide over supported Ga, Fe, and Cr-containing catalysts
Resumo
Oxydative dehydrogenation of ethane to ethelene over Ga-, Fe- and Cr-oxide systems has been investigated. CO2 was used as an oxidizing agent. The activity and stability of the synthesized catalysts were studied. The most efficient catalytic system was selected and the experimental conditions for the optimal conversion/selectivity ratio were found.
Catalysts based on hyperbranched pyridylphenylene polymers and palladium nanoparticles for the Suzuki—Miyaura cross-coupling reaction
Resumo
Synthesis of catalysts based on hyperbranched pyridylphenylene polymer and palladium nanoparticles (РРР-Рd) is described. Catalytic activity in the Suzuki—Miyaura cross-coupling reaction is studied for the interaction of bromobenzene with phenylboronic acid. Optimal reaction conditions providing maximum conversion (100%) of the initial compounds are established.
Thermal decomposition of ammonium perchlorate in the presence of bimetallic additives
Resumo
The catalytic activity of the thermolysis products of double complex compounds in the decomposition reaction of ammonium perchlorate was studied. The products used are C1.4N1.6H3CoFe (I), C6N8Co4Fe3 (II), O11Co4Fe3 (III), O8.5(CN)0.3Cu3Fe2 (IV), and reactive CuO. All active phases decrease the temperature of complete decomposition of NH4ClO4, and the order of temperature decreasing is the following: I ≈ II (120 °C) > IV > III (80 °C) ≫ CuO.
Dielectric spectroscopy study of cyanate ester oligomer curing kinetics
Resumo
The evolution of dielectric properties during the cyanate ester oligomer curing process was studied in the electric field frequencies range of 10–2—105 Hz. The kinetic of the curing process was investigated using the acquired data for complex dielectric permittivity and conductivity. It is demonstrated that, along with the formation of the polymer network, a microphase separation of the reaction intermediate, namely carbamate, takes place during the trimerization reaction. It is manifested in the frequency spectra as the Maxwell—Wagner polarization.
Acid-catalyzed isomerization of caryophyllene in the presence of SiO2 and Al2O3 impregnated with sulfuric acid
Resumo
The conversion of caryophyllene upon contact with Al2O3 and SiO2 impregnated with sulfuric acid was carried out, and the components of the resulting mixtures were identified. Having in hands such “standard” mixtures greatly facilitates identification of components of sesquiterpene fractions of essential oils and other mixtures of natural origin. The catalytic activity of silica gel impregnated with sulfuric acid (H+-SiO2) in the acid-catalyzed isomerization of caryophyllene is significantly higher than that for H+-Al2O3 and is comparable with the activity of concentrated sulfuric acid.
Synthesis, S-alkylation, and fungicidal activity of 4-(benzylideneamino)thioglycolurils
Resumo
A series of 1,3-disubstituted 4-benzylideneamino-5-thioxohexahydroimidazo[4,5-d]imidazol-2(1H)-ones (thioglycolurils) was synthesized via the reaction of 5,7-disubstituted 3-thioxoperhydroimidazo[4,5-e]-1,2,4-triazin-6-ones with hydroxy-, alkoxy-, and fluorocontaining benzaldehyde derivatives. An alkylation of the obtained thioglycolurils with methyl iodide or 4-bromobenzyl bromide provided the corresponding 6-benzylideneamino-5-alkylsulfanyl-3,3a,6,6a-tetrahydroimidazo[4,5-d]imidazol-2(1H)-ones. The fungicidal activity of some synthesized compounds against pathogens causing diseases of agricultural crops was studied.
3-(1-Methyl-1-nitroethyl-1-ONN-azoxy)-4-aminofuroxan. Synthesis and transformations of the amino group
Resumo
A four-step procedure to convert 4-(1-methyl-1-nitroethyl-1-ONN-azoxy)-3-cyanofuroxan into 3-(1-methyl-1-nitroethyl-1-ONN-azoxy)-4-aminofuroxan was developed. The pathways of transformation of the amino group of the synthesized compound into N-nitramino-, N-alkyl-N-nitramino-, N,N’-methylenediamino-, N,N’-methylene-N,N’-dinitramino-, and azo groups were studied.
An effective synthesis of polynuclear tetraamines, monomers for polyheteroarylenes
Resumo
An effective synthesis of polynuclear tetraamines via nucleophilic substitution of chlorine in 2-chloro-5-nitroaniline under ultrasonic irradiation followed by catalytic hydrogenation of dinitrodiaminoarenes in a flow reactor was proposed. A number of monomers, including those not described in the literature, were thus obtained. Two classes of polyheteroarylenes, namely, polynaphthoylenebenzimidazoles and polyphenylquinoxalines were synthesized by the polycyclocondensation in a supercritical carbon dioxide. Incorporation of trifluoromethyl substituents and flexible oxygen bridges into the structure of monomers allowed one to improve the solubility of the polymers. Some properties of synthesized polyheteroarylenes were investigated.
9-Ethyl-3-{6-(het)aryl-[1,2,5]oxadiazolo[3,4-b]pyrazin-5-yl}-9H-carbazoles: synthesis and study of sensitivity to nitroaromatic compounds
Resumo
5-(9-Ethyl-9H-carbazol-3-yl)-substituted 6-(het)aryl[1,2,5]oxadiazolo[3,4-b]pyrazines were synthesized by direct transition metal-free C—H functionalization in the pyrazine ring. Their photophysical and sensory properties with respect to nitrobenzene and 2,4-dinitrotoluene vapors were studied using a Nitroscan portable detector of nitro-explosive substances (Ekaterinburg, Russia).
Chlorination of 2-substituted 1-hydroxyindoles
Resumo
Chlorination of 1-hydroxyindole-5,6-dicarbonitriles and 1-hydroxypyrrolo[3,4-f]indole-5,7(1H,6H)-diones with N-chlorosuccinimide afforded previously unknown 3,3-dichloro-3Hindole 1-oxides instead of the expected 3-chloro-1-hydroxyindoles. The latter, however, were prepared in good yields by treatment of the above 3,3-dichloro-3H-indole 1-oxides with piperidine in ethanol. Reduction of 3,3-dichloro-5,6-dicyano-3H-indole 1-oxides with Zn in AcOH yielded the corresponding 3-chloroindole-5,6-dicarbonitriles.
Synthesis of androsteno[17,16-d]pyrazoles and androsteno[17,16-d]-2′-pyrazolines with pyrazolo[3,4-d]pyrimidine fragments
Resumo
Reactions of pyrazolo[3,4-d]pyrimidine-containing hydrazines with pregnenolone derivatives were studied. The reaction of 16α,17α-epoxy-3β-hydroxy-5-pregnen-20-one and its 3-O-acetyl derivative with 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine and 4-hydrazino-3-methyl-6-phenyl-1H-pyrazolo[3,4-d]pyrimidine afforded new androsteno[17,16-d]pyrazoles with pyrazolo[3,4-d]pyrimidine fragments. The reaction of 3β-hydroxypregna-5,16-dien-20-one and its 3-O-acetyl derivative with 4-hydrazino-3-methyl-6-phenyl-1H-pyrazolo[3,4-d]pyrimidine gave hydrazones at position 20 of the pregnenolone molecule, which upon melting undergo cyclization to androsteno[17,16-d]-2′-pyrazolines. Reflux of the hydrazone in mesitylene in the presence of MCPBA leads to a mixture of three products, namely, androsteno[17,16-d]-2′-pyrazoline, androsteno[17,16-d]pyrazole, and dodecahydro-13H-phenanthro[1′,2′:5,6]pyrano[2,3-d]pyrazole derivative resulting from the oxidative expansion of the steroid cyclopentane ring D.
Brief Communications
A new approach for the acceleration of large-scale serial quantum chemical calculations of docking complexes
Resumo
A new approach to radical accelerate large-scale quantum chemical calculations of docking complexes, which require large computational times, is proposed. It takes into account the local nature of protein interaction with ligands and is based on a formation of special groups of atoms, which include the compactly located ligands and the protein atoms surrounding them. The procedure based on this approach allowed more than twice to reduce the time of a very resource-consuming calculation with respect to our previous high-speed semi-empirical method without a noticeable decrease in accuracy and provided a level of the time consumption appropriate for the large-scale serial calculations of such complexes.
Comparative reactivity of hydroxyketones and their derivatives in the reactions with N,S-nucleophiles
Resumo
The reactions of thiosemicarbazide (TSC), thiocarbohydrazide, and hydrazine thiocarbamate with oxyketones, haloketones, and derivatives of acetylenic alcohols were studied. Thiadiazines bearing exocyclic thio and hydrazo groups were synthesized. Acetylenic alcohols react with TSC to give the corresponding thiazolidines. The reactions of halo derivatives of acetylenic alcohols with TSC are complicated by side reactions.
Synthesis of N,N′-di(1-adamantyl)bispidin-9-ones
Resumo
The condensation product of adamantan-1-amine with formaldehyde, 1,3,5-tri(1-adamantyl)-1,3,5-triazacyclohexane, was treated with three different types of ketones: symmetric (RCH2)2CO, nonsymmetric RCH2COCH3, and acetone to obtain 1,5-R-N,N′-di(1-adamantyl) bispidin-9-ones, N,N′-di(1-adamantyl)-1-[(1-adamantylamino)methyl]-5-methylbispidin-9-one, and N,N′-di(1-adamantyl)-1,5-bis[(1-adamantylamino)methyl]bispidin-9-one. 1,5-R-N,N′-Di(1-adamantyl)bispidin-9-ones were reduced with sodium borohydride to 1,5-R-N,N′-di(1-adamantyl)bispidin-9-ols.