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51.
The use of dichloromethane for the extraction of amines may lead to the formation of artifacts. Dichloromethane reacts rapidly (37.5 degrees) with brompheniramine, diphenylpyraline, cyclizine, cyproheptadine but not with antazoline and lignocaine. This difference in reactivity as well as the thin-layer chromatographic, gas-liquid chromatographic, nuclear magnetic resonance, and mass spectrometric characteristics of cyclizine and diphenylpyraline chloromethochlorides are investigated. 相似文献
52.
Tropinone has been reduced under various conditions of time, temperature, solvent and reducing agent. The stereoisomeric composition of the reduction product was determined by infra-red spectrophotometry. The results indicate the participation of kinetic and thermodynamic factors in the stereoisomeric course of the reduction, the former depending upon the effective size of the reducing species. An assignment of the order of size of reducing species in particular solvents is made.
The stereoisomeric composition of the product of equilibration is independent of the reagent and the temperature in the system studied. 相似文献
53.
P.M. Beckett 《International Journal of Non》1985,20(4):261-271
The motion of a spherical particle contained within a rotating fluid is analysed using equations of classical mechanics. Conditions are established under which the second order differential system simplifies to the well known Svedberg equation which describes the radial motion in centrifugation theory. The complete particle trajectories are obtained by solving the second order system numerically and approximations to these are derived using perturbation methods. 相似文献
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Michael A. Beckett Martin P. Rugen-Hankey K. Sukumar Varma 《Journal of Sol-Gel Science and Technology》2006,39(2):95-101
The reaction of metaborate esters (RO)3B3O3 [R = Me, Et, ClCH2CH2–, Cl3CCH2–, ClCH2CH2CH2–, (ClCH2)2CH–] with Si(OR)4 (R = Me, Et), either neat or in dry propan-2-one or dry THF at room temperature, led to gels which when dried and heated
in air for 20 mins at 600°C afforded borosilicate glasses in high ceramic yields. The dried gels and glasses were characterized
by elemental analysis, TGA, IR, and powder XRD, and solid-state MAS 29Si and 11B NMR. The gelling reaction was investigated by solution 11B and 29Si NMR. These NMR studies indicated B–O–Si reaction intermediates and a mechanism involving alkoxy exchange and various condensation/elimination
reactions of the borosilicate esters have been proposed. 相似文献
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Beckett MA Rugen-Hankey MP Timmis JL Varma KS 《Dalton transactions (Cambridge, England : 2003)》2008,(11):1503-1506
The reaction of metal alkoxides M(OR)4 (M = Ti, Zr; R = organyl) with (MeO)3B3O3 (1 : 0.67) in dry propan-2-one at room temperature led to gels which when dried and calcined in air for 24 h at 500-1000 degrees C afforded bi-phased mixed-oxide materials formulated as 4TiO2 x 3B2O3 and ZrO2 x B2O3 in high ceramic yields and purity; the B2O3 phases of these materials were amorphous. The materials remained amorphous upon calcination at lower temperatures. The TiO2 phase of the 4TiO2 x 3B2O3 was crystalline when calcined at higher temperatures with either anatase (600 degrees C) or rutile (>800 degrees C) being obtained. The ZrO2 phase of the ZrO2 x B2O3 was crystalline when calcined at higher temperatures and was obtained as a metastable tetragonal phase (<700 degrees C) or baddeleylite (>800 degrees C). In a similar reaction, Al(O(i)Pr)3 (2 : 1) gave a bi-phased aluminium borate-boron oxide (Al18B4O(33).7B2O3) after calcination at >700 degrees C. The dried gels and oxide materials were all characterized by elemental analysis, TGA-DSC, and powder XRD. 相似文献
59.
Lukas Wursthorn Kristen Beckett Jacob O. Rothbaum Dr. Robin M. Cywar Clarissa Lincoln Prof. Yosi Kratish Prof. Tobin J. Marks 《Angewandte Chemie (International ed. in English)》2023,62(4):e202212543
Nylon-6 is selectively depolymerized to the parent monomer ϵ-caprolactam by the readily accessible and commercially available lanthanide trisamido catalysts Ln(N(TMS)2)3 (Ln=lanthanide). The depolymerization process is solvent-free, near quantitative, highly selective, and operates at the lowest Nylon-6 to ϵ-caprolactam depolymerization temperature reported to date. The catalytic activity of the different lanthanide trisamides scales with the Ln3+ ionic radius, and this process is effective with post-consumer Nylon-6 as well as with Nylon-6+polyethylene, polypropylene or polyethylene terephthalate mixtures. Experimental kinetic data and theoretical (DFT) mechanistic analyses suggest initial deprotonation of a Nylon terminal amido N−H bond, which covalently binds the catalyst to the polymer, followed by a chain-end back-biting process in which ϵ-caprolactam units are sequentially extruded from the chain end. 相似文献
60.