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81.
82.
V. V. Danilevich L. A. Isupova I. G. Danilova R. A. Zotov V. A. Ushakov 《Russian Journal of Applied Chemistry》2016,89(3):343-353
Activated alumina desiccants modified with NaOH and KOH were synthesized from the product of a centrifugal thermal activation of gibbsite, with the subsequent hydration in an acid or alkaline medium, and their properties were studied. It was shown that the modification makes it possible to raise the dynamic capacity of desiccants produced from pseudoboehmite by up to a factor of 2 via formation of new super-strong basic centers the concentration of which grows with increasing content of an alkaline oxide. A correlation was found between the total concentration of basic centers on the surface of the desiccants and their dynamic capacity in drying of both dry and humid air. Use of the modified desiccants with high static and dynamic capacity will make it possible to improve the drying efficiency. 相似文献
83.
V. V. Danilevich L. A. Isupova E. A. Paukshtis V. A. Ushakov 《Kinetics and Catalysis》2014,55(3):372-379
In the production of alumina desiccants by extrusion, the introduction of sulfuric acid at the stage of preparing a mouldable paste based on hydroxides containing bayerite or pseudoboehmite increases the sorption capacity of the product. This effect is most pronounced for the pseudoboehmite-based materials. The dynamic capacity of these desiccants increases to the level characteristic of the bayerite-containing hydroxide (>5 g H2O/100 cm3) for a dew point of ?40°C and a contact time of 1.5 s), and their static capacity exceeds this value (increasing from 21.13 to 23.1 g H2O/100 cm3). This procedure changes the phase composition and textural characteristics of the pseudoboehmite-based desiccants and increases Brønsted acidity and generates strong Lewis acid sites on the surface of all oxides. The dynamic capacity of desiccants with similar textural characteristics depends on the acid-base properties of their surface. 相似文献
84.
Fedorov P. P. Ushakov S. N. Uslamina M. A. Chernova E. V. Kuznetsov S. V. Voronov V. V. Düvel A. Heitjans P. Pynenkov A. A. Nishchev K. N. Osiko V. V. 《Crystallography Reports》2018,63(5):837-843
Crystallography Reports - Proceeding from the phase diagram of the CaF2–SrF2 system, the stability of crystal–melt interface of solid solution against constitutional supercooling has... 相似文献
85.
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87.
Multinuclear dynamic NMR spectroscopy of 5-trifluoromethylsulfonyl-1,3,5-dioxaazinane (4) revealed the existence of two close in energy chair conformers with differently oriented CF3 groups with respect to the ring. Of the two alternative routes for their interconversion, the ring inversion path with intermediate formation of the corresponding 2,5-twist-conformer is preferred, with the energy barrier of 11.2 kcal/mol in excellent agreement with the experimental value (11.7 kcal/mol). The Perlin effect is studied experimentally and calculated theoretically for all CH2 groups and found to be subject to the nature of the adjacent heteroatoms O and N, respectively. 相似文献
88.
Boris A. Trofimov Lyubov N. Sobenina Zinaida V. Stepanova Olga V. Petrova Igor A. Ushakov Albina I. Mikhaleva 《Tetrahedron letters》2008,49(24):3946-3949
4,5,6,7-Tetrahydroindoles undergo a rapid, facile (rt, 60 min) ethynylation with ethyl 3-halo-2-propynoates upon grinding with solid K2CO3 (without solvent) at C-2 of the tetrahydroindole ring to afford ethyl 3-(4,5,6,7-tetrahydroindol-2-yl)-2-propynoates in 62–90% yield. 相似文献
89.
V. I. Meshcheryakov M. Yu. Moskalik A. Kelling U. Schilde I. A. Ushakov B. A. Shainyan 《Russian Journal of Organic Chemistry》2008,44(2):311-316
Acid-catalyzed reaction of trifluoromethanesulfonamide with paraformaldehyde in ethyl acetate led to the formation of oxymethylated products that did not form in the reaction carried out in sulfuric acid. Following products were obtained: 5-trifluoromethylsulfonyl-1,3-dioxazinane, 3,7-bis-(trifluoromethylsulfonyl)-1,5,3,7-dioxadiazocane, and a complex of trifluoromethanesulfonamide with 2,4,8,10-tetraoxospiro[5,5]undecene, 1:1. The spiroring resulted from the cyclization of pentaerythritol under the action of formaldehyde. The pentaerythritol formed in its turn by oxymethylation of the methyl group of ethyl acetate with paraformaldehyde followed by the reduction of the COOEt group into CH2 OH by the formaldehyde. 相似文献
90.
Afonin AV Vashchenko AV Ushakov IA Zorina NV Schmidt EY 《Magnetic resonance in chemistry : MRC》2008,46(5):441-447
The N-H...X (X = N,O,S) intramolecular hydrogen bond in the series of 2(2'-heteroaryl)pyrroles and their trifluoroacetyl derivatives is examined by the (1)H, (13)C, (15)N spectroscopy and density functional theory (DFT) calculations. The influence of the hydrogen bond on coupling and shielding constants is considered. It is shown that the N-H...N intramolecular hydrogen bond causes a larger increase in the absolute size of the (1)J(N,H) coupling constant and a larger deshielding of the bridge proton than the N-H...O hydrogen bond. The effect of the N-H...S interaction on the (1)J(N,H) coupling constant and the shielding of the bridge proton is small. The NMR parameter changes in the series of the 2(2'-heteroaryl)pyrroles due to N-H...X hydrogen bond and the series of the 1-vinyl-2-(2'-heteroaryl)-pyrroles due to C-H...X hydrogen bond have the same order. The proximity of the nitrogen, oxygen or sulfur lone pair to the F...H hydrogen bridge quenches the trans-hydrogen bond spin-spin couplings (1h)J(F,H-1) and (2h)J(F,N). 相似文献