Structure and stability of the SiH3O2: Radical

A quantum chemical ab initio study of the electronic structure and force constants of the SiH₃O ₂ ^. radical is reported. The minimum on the potential surface corresponds to a C_s symmetry structure (the²A¹¹ term). The Hartree-Fock solution with the minimal energy for this structure does not satisfy the aufbau principle. The calculated enthalpy of SiH₃O ₂ ^. formation from SiH ₃ ^. and O₂(³∑_g ^-) is approximately −30 kcal/mole. Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 25–30, January–February, 1994. Translated by L. Smolina     

Synthesis of hydrocarbons from CO and H2 in the presence of Co-Ru and Co-Pd catalysts containing aluminum oxide

The influence of additions of 0.1–0.5% Pd or Ru in a 10% Co/Al₂O₃ catalyst on its activity and selectivity in the synthesis of liquid hydrocarbons from CO and H₂ has been studied. It has been shown that the bimetallic systems make it possible to carry out the synthesis of hydrocarbons with a higher extent of conversion of CO and a higher yield of C ₅ ⁺ carbons in comparison with the original Co catalyst. Co-Ru catalysts exhibit exceptionally high selectivity (up to 80%) with respect to the formation of liquid products. It has been demonstrated by temperature-programmed reduction (TPR) that the introduction of Pd an dRu promotes the reduction of Co at lower temperatures and the formation of cobalt aluminates.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 60–64, January, 1992.     

Cobalt/silica gel system as a chemisorbent for oxygen

A study has been made of oxygen chemisorption and the phase composition of cobalt/silica gel samples containing from 1.1 to 7.7% Co by weight. Reduction in hydrogen leads to the formation of metallic cobalt with a crystal size of about 50 Å. The quantity of chemisorbed O₂ at 20°C increases in proportion to the increase of [Co]. The uptake of O₂ is essentially completed at 300°C with the formation of Co₃O₄. The high adsorption capacity for O₂ is preserved unchanged in repetitive reduction-oxidation cycles. The residual content of O₂ in the gas after passage through the layer of the cobalt/silica gel chemisorbent is 3·10^–6% by volume.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya, Khimicheskaya, No. 1, pp. 40–43, January, 1992.     

Comparative study of Co3O4-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane

In this work, various Co₃O₄-ZSM-5 catalysts were prepared by the microwave hydrothermal method (MH-Co₃O₄@ZSM-5), dynamic hydrothermal method (DH-Co₃O₄@ZSM-5), and conventional hydrothermal method (CH-Co₃O₄/ZSM-5). Their catalytic oxidation of dichloromethane (DCM) was analyzed. Detailed characterizations such as X-ray diffractometer (XRD), scanning microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), H₂ temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of O₂ (O₂-TPD), temperature-programmed desorption of NH₃ (NH₃-TPD), diffuse reflectance infrared Fourier-transform spectra with NH₃ molecules (NH₃-DRIFT), and temperature-programmed surface reaction (TPSR) were performed. Results showed that with the assistance of microwave, MH-Co₃O₄@ZSM-5 formed a uniform core-shell structure, while the other two samples did not. MH-Co₃O₄@ZSM-5 possessed rich surface adsorbed oxygen species, higher ratio of Co³⁺/Co²⁺, strong acidity, high reducibility, and oxygen mobility among the three Co₃O₄-ZSM-5 catalysts, which was beneficial for the improvement of DCM oxidation. In the oxidation of dichloromethane, MH-Co₃O₄@ZSM-5 presented the best activity and mineralization, which was consistent with the characterizations results. Meanwhile, according to the TPSR test, HCl or Cl₂ removal from the catalyst surface was also promoted in MH-Co₃O₄@ZSM-5 by their abundant Brønsted acid sites and the promotion of Deacon reaction by Co₃O₄ or the synergistic effect of Co₃O₄ and ZSM-5. According to the results of in situ DRIFT studies, a possible reaction pathway of DCM oxidation was proposed over the MH-Co₃O₄@ZSM-5 catalysts.     

2H-imidazole-N-oxides as spin traps

The capacity of 2H-imidazole-1-oxides, which contain an aldonitrone group, for spin capture was investigated. The parameters of spin adducts with^.OH,^.CH₃, and^.CH₂OH radicals are reported.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1064–1068, May, 1992.     

Reaction of diazoalkanes with unsaturated compounds. 11. Relative reactivity of olefins on catalytic cyclopropanation with diazomethane and palladium catalysts

The relative reactivity of unsaturated compounds on catalytic cyclopropanation with diazomethane in the presence of catalysts based on Pd²⁺ [Pd(OAc)₂, Pd(acac)₂, (PPh₃)₂·PdCl₂] has been studied using competing reactions. An interconnection was shown between the relative reactivity of the olefins and the coordinating activity of the C=C bond depending on its strain and spatial environment.For previous communication, see [1].Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa; N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2353–2361, October, 1992.     

Phase composition and formation of cobalt-copper cement catalysts

Using x-ray phase analysis, DTA, DTG, and temperature-programmed reduction, we have studied the phase composition and formation of cobalt-copper cement catalysts obtained by chemical mixing of hydroxocarbonates of cobalt (CoHC) and copper (CuHC) with the aluminocalcium cement talyum, consisting of CaAl₂O₄ and CaAl₄O₇, in an aqueous ammonia medium. We have shown that when the components are mixed, exchange reactions occur with development of new phases of cobalt and copper hydroxoaluminates, calcite, gibbsite, Cu(OH)₂, CuO. We found that CaAl₂O₄ is more reactive than CaAl₄O₇. We have obtained data on the change in the phase composition upon thermolysis and reduction in H₂.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 48–54, January, 1992.     

Selective synthesis of di(propen-1-yl)sulfone and di(propen-1-yl)sulfoxide

Convenient selective methods of synthesis of the title compounds, based on oxidation of di(propen-1-yl)sulfide with 30% H₂O₂, have been developed.Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 664033 Irkutsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 675–679, March, 1992.     

Effect of Calcination Temperature on Surface Oxygen Vacancies and Catalytic Performance Towards CO Oxidation of Co3O4 Nanoparticles Supported on SiO2

Co₃O₄/SiO₂ catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were char-acterized with X-ray diffraction (XRD), laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and X-ray absorption fine structure (XAFS) spectroscopy. Both XRD and Raman spectroscopy only detect the ex-istence of Co₃O₄ crystallites in all catalysts. However, XPS results indicate that excess Co²⁺ ions are present on the surface of Co₃O₄ in Co₃O₄(200)/SiO₂ as compared with bulk Co₃O₄. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co₃O₄ in Co₃O₄(200)/SiO₂, and XAFS results demonstrate that Co₃O₄ in Co₃O₄(200)/SiO₂ con-tains excess Co²⁺. Increasing calcination temperature results in oxidation of excess Co²⁺ and the decrease of the concentration of surface oxygen vacancies, consequently the for-mation of stoichiometric Co₃O₄ on supported catalysts. Among all Co₃O₄/SiO₂ catalysts,Co₃O₄(200)/SiO₂ exhibits the best catalytic performance towards CO oxidation, demon-strating that excess Co²⁺ and surface oxygen vacancies can enhance the catalytic activity of Co₃O₄ towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silica-supported Co₃O₄ catalysts and highlight the important role of surface oxygen vacancies on Co₃O₄.     

Coumarins fromPhlojodicarpus sibiricus

Phlojodicarpin [8-(2,3-epoxy-1-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 143–145°C, [] _D ²⁵ -37.5°], and isophlojodicarpin [8-(1,2-epoxy-3-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 132–134°C, [] _D ²⁵ -102.5°] have been isolated from the epigeal part ofPhlojodicarpus sibiricus. The results of the IR, UV, PMR, and mass spectrometry of these compounds are given.Institute of Chemistry, Academy of Sciences of the Mongolian Peoples' Republic, Ulan-Bator. Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 47–49, January–February, 1981.     

Coumarins of Fraxinus mandschurica and F. potamophila

Summary The leaves ofFraxinus mandschurica Rupr. and the bark ofF. potamophila Herd. have yielded esculetin, fraxinol, and a new coumarin C₁₀H₈O₅, mp 228–230°C which we have called isofraxetin. On the basis of NMR and UV spectroscopy it has been established that isofraxetin is 5,7-dihydroxy-7-methoxycoumarin.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Institute of Chemistry, Academy of Sciences of the Turkmen SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 493–497, July–August, 1973.     

Template synthesiS: Geometrical and electronic structures of the Fe nitrosyl complex formed by bis(S-methylisothiosemicarbazone)-2,4-pentandione

Sodium acetylacetonate reacts with S-metliylisothiosemicarbazidium nitrate and Fe(NO₃)₃ · 9H₂O in ethanol to make [Fe(HL)NO]NO₃, in which H₃L is bis(S-methyl-isothiosemicarbazone)-2,4-puntandione. The [Fe(HL)NO]⁺ cation has a square pyramidal structure with the HL^2- arranged around the central ion in the basal plane and the nitrogen atom of the NO group in the apical position, with the iron atom diverging from the plane of the base of the pyramid by 0.477 Å. The FeN0 moiety has a linear structure (FeNO = l72.7°). XRD, IR, and Mössbauer spectroscopy have been combined with calculations on the electronic structure to demonstrate that the Fe-NO bond is covalent.Chemical Institute, Academy of Sciences of Moldavian SSR. Applied Physics Institute, Academy of Sciences of the Moldavian SSR. Kishinev. Institute of Crystallography, Academy of Sciences of the USSR. Kurnakov Institute for General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No, 3, pp. 376–381, May–June, 1991. Original article submitted February 18, 1991.     

Oxygen chemisorption on divalent chromium ions in chromosilicate systems

A study has been made of the chemisorption of O₂ from various gaseous media on divalent chromium ions in chromosilicate systems under dynamic conditions. After passing through the chemisorbent layer the residual O₂ content of the gaseous mixtures is 10^–6–10^–7 vol. %. The adsorption capacity of the chemisorbents increases in proportion to their Cr(II) content and decreases as the moisture content increases in the gas mixture from which the oxygen is absorbed. The chemisorbents can be repeatedly regenerated by treating them with hydrogen.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2500–2505, November, 1992.     

Synthesis and properties of phosphorus-tungsten heteropolyacid H6P2W21O71

An electromembrane method has been proposed for the synthesis of H₆P₂W₂₁O₇₁, its resistance to heat in the solid state has been studied, and the Hammett acidity functions of concentrated aqueous solutions measured.Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660049. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 494–497, March, 1992.     

The isocoumarin artemidinal from Artemisia dracunculus

Summary Artemidinal, C₁₀H₆O₃, which is isocoumarin with an aldehyde group at C₃, has been isolated from the epigeal part ofArtemisia dracunculus.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 257–259, May–June, 1971.     

Investigation of rehydration of pyrogenic silica by temperature-programmed desorption method

The rehydration of pyrogenic silica has been investigated by means of thermodesoprtion mass spectrometry. It is concluded that the process kinetics are determined by diffusion of water molecules within the SiO₂ globules.Institute of Surface Chemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoretichekaya i Éksperimental'naya Khimiya, No. 1, pp. 94–99 January–February, 1991. Original article submitted August 22, 1989.     

Mass spectrometry of negative ions and the stereochemistry of organic compounds. IV. Acetates of epimeric diterpene glycols

Summary 1. It has been established that the fragmentation of the molecular negative ions of the diacetates of sclareol and of 13-episclareol takes place with the splitting out of the fragments Ac, OAc, CH₂CO, AcOH, CH₃, and CH=CH₂ without skeletal rearrangements.2. The relative yields of the negative ions formed depend on the stereochemistry of the molecules of the compounds investigated.Institute of Chemistry, Bashkir Branch of the Academy of Sciences of the USSR, Ufa. Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 454–457, July–August, 1978.     

Kinetics of metal ion sorption on clinoptilolite

From an investigation into the sorption kinetics of Na⁺, K⁺, and Sr²⁺ ions from standard solutions on finely dispersed clinoptilolite incorporated in a highly permeable inert polyacrylamide gel we have determined the characteristic kinetic size of clinoptilolite and the diffusion coefficients for Na⁺, K⁺, and Sr²⁺ in the clinoptilolite microcrystallites and transport pores. Diagrams have been constructed to enable a valid selection of kinetic models for sorption of the ions from any solutions on clinoptilolite.Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 690022 Vladivostok. V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 273–277, February, 1992.     

X-Ray diffraction study of solid-state photoisomerization products [Co(NY3)5NO2]XY (X,Y = Cl,Br, I,NO3)

Complexes [Co(NH₃)₅NO₂]XY and [Co(NH₃)₅ONO]XY (X,Y=Cl, Br, I, NO₃) have been studied by the X-ray diffraction method. The unit cell parameters were refined for the nitro isomers and determined for the nitrito isomers. We have analyzed changes in the latter arising during the nitro-nitrito photoisomerization and the reverse nitrito-nitro thermal isomerization. The topotaxial character of the structural rearrangement has been shown. The X-ray diffraction data obtained were compared with IR and kinetic data.Institute of Solid State Chemistry and Processing of Mineral Raw Materials, Siberian Branch, Russian Academy of Sciences. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 128–140., July–August, 1993.Translated by T. Yudanova     

ESR study of electron interaction in a Tc/Al2O3 system

An investigation was made into the nature of paramagnetic centers in a Tc/Al₂O₃ system under varying conditions as to heat treatment and technetium content, and in O₂ and CO adsorption environments. It was found that in the case of reduction at 573 K Tc²⁺ ions and, conceivably, other ionic forms developed and stabilized on the carrier surface. After reduction at 973 K two types of electron center appeared, whose concentration increased as reduction was prolonged. Signals were observed in the low fields (3–20 mT) of the ESR spectra having g₁ 13.5 and g₂>30, which could be assigned to free charge carriers in a cluster of metal atoms or ions. Adsorption of O₂ at 300 K caused O ₂ ^– ion radicals to form on the surface of the reduced Tc/Al₂O₃ samples, both electron centers and technetium ions constituting the electron donors. In the case of CO adsorption paramagnetic (CO) ₂ ^– particles appeared on the Tc/Al₂O₃ samples after prolonged exposure. On reaction with O₂ two types of O ₂ ^– ion-radical with differing thermal stability were formed.Institute of Physical Chemistry, Russian Academy of Sciences, Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1972–1978, September, 1992.