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91.
92.
Tomáš Weidlich Libor Dušek Barbora Vystrčilová Aleš Eisner Petr Švec Aleš Růžička 《应用有机金属化学》2012,26(6):293-300
The potential catalytic activity of selected C,N‐chelated organotin(IV) compounds (e.g. halides and trifluoroacetates) for derivatization of both dimethyl carbonate (DMC) and diethyl carbonate (DEC) was investigated. Some tri‐, di‐ and monoorganotin(IV) species (LCN(n‐Bu)2SnCl (1), LCN(n‐Bu)2SnCl.HCl (1a), LCN(n‐Bu)2SnI (2), LCNPh2SnCl (3), LCNPh2SnI (4), LCN(n‐Bu)SnCl2 (5), LCNSnBr3 (6) and [LCNSn(OC(O)CF3)]2(μ‐O)(μ‐OC(O)CF3)2 (7)) bearing the LCN moiety (LCN = 2‐(N,N‐dimethylaminomethyl)phenyl‐) were assessed as catalysts for reactions of both DMC and DEC with various substituted anilines. The catalytic activities of 4 and 7 for derivatization of DMC with p‐substituted phenols were studied for comparison with the standard base K2CO3/Silcarbon K835 catalyst (catalyst 8). The composition of resulting reaction mixtures was monitored by multinuclear NMR spectroscopy, GC and GC‐MS techniques. In general, catalysts 1, 3 and 7 exhibited the highest catalytic activity for all reactions studied, while some of them yielded selectively carbonates, carbamates, lactam or substituted urea. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
93.
94.
Vít Kremláček Prof. Milan Erben Prof. Roman Jambor Prof. Aleš Růžička Dr. Jan Turek Dr. Elena Rychagova Prof. Sergey Ketkov Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(22):5668-5671
The 2,1-benzazaarsole ( 1 ) showed a diene-like reactivity towards selected alkynes RC≡CR (R=CO2Me, C5F4N) thus forming 1-arsa-1,4-dihydro-iminonaphthalenes 2 a and 3 a as hardly isolable intermediates, that underwent facile CH→NH proton migration leading to before elusive substituted 1-arsanaphthalenes 2 b and 3 b that could be completely structurally characterized. 相似文献
95.
Pavol Brunovský Aleš Černý Ján Komadel 《European Journal of Operational Research》2018,264(3):1159-1171
We study optimal liquidation of a trading position (so-called block order or meta-order) in a market with a linear temporary price impact (Kyle, 1985). We endogenize the pressure to liquidate by introducing a downward drift in the unaffected asset price while simultaneously ruling out short sales. In this setting the liquidation time horizon becomes a stopping time determined endogenously, as part of the optimal strategy. We find that the optimal liquidation strategy is consistent with the square-root law which states that the average price impact per share is proportional to the square root of the size of the meta-order (Bershova & Rakhlin,2013; Farmer et?al., 2013; Donier et?al., 2015; Tóth (2016).Mathematically, the Hamilton–Jacobi–Bellman equation of our optimization leads to a severely singular and numerically unstable ordinary differential equation initial value problem. We provide careful analysis of related singular mixed boundary value problems and devise a numerically stable computation strategy by re-introducing time dimension into an otherwise time-homogeneous task. 相似文献
96.
97.
Michael Hrušák Tamás Mátrai Aleš Nekvinda Václav Vlasák Ondřej Zindulka 《Acta Mathematica Hungarica》2014,142(1):1-30
A metric space (X,d) is monotone if there is a linear order < on X and a constant c>0 such that d(x,y)≦cd(x,z) for all x<y<z∈X. Properties of continuous functions with monotone graph (considered as a planar set) are investigated. It is shown, for example, that such a function can be almost nowhere differentiable, but must be differentiable at a dense set, and that the Hausdorff dimension of the graph of such a function is 1. 相似文献
98.
Ilya Kuselman Francesca Pennecchi Aleš Fajgelj Yury Karpov 《Accreditation and quality assurance》2013,18(1):3-9
The present paper is a review of the main theoretical and technical aspects of human error treatment (error modelling, reduction and quantification) as applied in aviation, engineering, medicine and other fields. The aim of the review is to attract the attention of analysts and specialists in metrology and quality in chemistry to the human error problem and its influence on the reliability of test results of chemical composition and associated measurement uncertainty. Therefore, the subject of human error is interpreted in the review in application to the conditions of a chemical analytical laboratory. 相似文献
99.
Drahomír Hnyk Josef Holub Aleš Růžička Zdeňka Padělková Michael Bühl 《Structural chemistry》2013,24(3):927-932
Two iodo derivatives of closo-CB11H12 ?, i.e., 12-I-1-CB11H11 ? (C 5v symmetry) and 7-I-1-CB11H11 ? (C s symmetry), were prepared (the latter for the first time) and the influence of differently positioned iodine substituents on the geometry of the CB11 icosahedral core was structurally examined both by X-ray diffraction and quantum-chemical computation at the MP2 level. Observed and computed molecular geometries are in overall agreement. Supramolecular architectures of these two anionic substituted monocarboranes are shown. According to DFT computations at the ZORA-SO/BP86 level, the 11B chemical shifts of the boron atoms to which iodine substituents are bonded are dominated by spin–orbit coupling. Different positions of iodine atoms in these two isomers may result in different acidities of the (C)-H atoms in the icosahedral bodies, as suggested by visually analyzing the corresponding lowest unoccupied molecular orbitals. 相似文献
100.
Aleš Rajchl Ladislava Drgová Adéla Grégrová Helena Čížková Rudolf Ševčík Michal Voldřich 《Analytical and bioanalytical chemistry》2013,405(14):4737-4745
DART (direct analysis in real time), a novel technique with wide potential for rapid screening analysis, coupled with high-resolution time-of-flight mass spectrometry (TOF-MS) has been used for quantitative analysis of 5-hydroxymethylfurfural (5-HMF), a typical temperature marker of food. The DART/TOF-MS method was optimised and validated. Quantification of 5-HMF was achieved by use of a stable isotope-labelled 5-HMF standard prepared from glucose. Formation of 5-HMF from saccharides, a potential source of overestimation of results, was evaluated. Forty-four real samples (honey and caramelised condensed sweetened milk) and 50 model samples of heated honey were analysed. The possibility of using DART for analysis of heated samples of honey was confirmed. HPLC and DART/TOF-MS methods for determination of 5-HMF were compared. The correlation equation between these methods was DART?=?1.0287HPLC?+?0.21340, R 2?=?0.9557. The DART/TOF-MS method has been proved to enable efficient and rapid determination of 5-HMF in a variety of food matrices, for example honey and caramel. 相似文献