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101.
102.
Summary The effect of organic cosolvent on the rate constants and activation parameters of oxidation of coordinativelybound thiocyanate with peroxodisulphate was investigated in mixtures of water with methanol,i-propanol andt-butanol. The thermodynamic transfer functions, corresponding to the transfer of reactants and activated complex from water to the solvent mixtures were evaluated from kinetic measurements and from the solubilities of corresponding salts. The experimental results are interpreted in terms of the solvation of both the initial state and the activated complex. 相似文献
103.
J. Murín D. Olčák J. Oravcová M. Rákoš K. Jelšovská 《Czechoslovak Journal of Physics》1981,31(3):313-323
Nuclear magnetic resonance of protons of crystallization water in isomorphous paramagnetic and diamagnetic monohydrates MeSO4. 1 H2O with Me = Mn2+, Fe2+, Ni2+ and Mg2+ is studied in the present paper. Proton NMR spectra in paramagnetic hydrates are asymmetric and their second moments, M2, depend linearly on the square of the induction of the external magnetic field B0. NMR spectrum of diamagnetic hydrate MgSO4. 1 H2O is symmetric and its shape and the second moment do not change with B0. The parameters M20 andK which characterize nuclear dipole-dipole interaction of protons and interaction of protons and paramagnetic ions, respectively, are derived from experimentally obtained dependences M2 vs B
0
2
and on the other hand, they are calculated by means of crystallographic data for substances studied. Calculations were realized in approximation where two nearest neighbour ions Me2+ to each water molecule are considered. The influence of the demagnetizing magnetic field of the sample was neglected. 相似文献
104.
A Rhodium Nanoparticle–Lewis Acidic Ionic Liquid Catalyst for the Chemoselective Reduction of Heteroarenes
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Alena Karakulina Aswin Gopakumar Dr. İsmail Akçok Bastien L. Roulier Dr. Thomas LaGrange Dr. Sergey A. Katsyuba Dr. Shoubhik Das Prof. Dr. Paul J. Dyson 《Angewandte Chemie (International ed. in English)》2016,55(1):292-296
We describe a catalytic system composed of rhodium nanoparticles immobilized in a Lewis acidic ionic liquid. The combined system catalyzes the hydrogenation of quinolines, pyridines, benzofurans, and furan to access the corresponding heterocycles, important molecules present in fine chemicals, agrochemicals, and pharmaceuticals. The catalyst is highly selective, acting only on the heteroaromatic ring, and not interfering with other reducible functional groups. 相似文献
105.
Dr. Alena S. Pankova Dr. Pavel Golubev Ilia A. Molin Dr. Nikolai V. Rostovskii 《European journal of organic chemistry》2023,26(34):e202300573
Exclusive formation of 5-aryl-2-trimethylsilyl-4H-pyran-4-ones is accomplished by a regioselective cyclization of 2-aryl-1-ethoxy(hydroxy)-5-(trimethylsilyl)pent-1-en-4-yn-3-ones. This cyclization occurs in a 6-endo-dig mode through addition to the β-atom of the TMS substituted triple bond. The reaction was found to be general for a range of ethoxyenynones upon heating in glacial acetic acid and for analogous hydroxyenynones in diphenyl ether. Plausible mechanistic explanation and possible post-modifications of resulting pyranones are offered. 相似文献
106.
Stepanka Kuckova Tatiana Anatolievna Smirnova David Straka Alena Meledina Jiri Santrucek Karin Humpolakova Martina Hoskova Pavel Cejnar Radovan Hynek 《Journal of separation science》2023,46(13):2300064
The aim of this work is to offer an alternative or complementary analytical tool to the time-consuming and expensive methods commonly used for the recognition of animal species according to their hair. The paper introduces a simple and fast way for species differentiation of animal hairs called in-sample digestion. A total of 10 European animal species, including cat, cow, common degu, dog, fallow deer, goat, horse, sika deer, rabbit, roe deer, and 17 different breeds of dogs were examined using specific tryptic cleavage directly in hair followed by matrix-assisted laser desorption/ionization–time of flight mass spectrometry and liquid chromatography-electrospray ionization quadrupole time of flight. Principal component analysis was used for the subsequent mass spectrometric data evaluation. This novel approach demonstrates the ability to distinguish among individual animal species, which is supported by finding characteristic m/z values obtained by the mass spectrometry for each animal species. The approach was successfully tested on two “blind” samples. On the other hand, the attempt to distinguish among hairs of different dog breeds has not been successful due to the very similar protein composition and their amino acid sequences. 相似文献
107.
Fleming MJ McManus HA Rudolph A Chan WH Ruiz J Dockendorff C Lautens M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2112-2124
New enantioselective syntheses of the B/C hexahydrobenzo[c]phenanthridine alkaloids (+)-homochelidonine, (+)-chelamidine, (+)-chelidonine, (+)-chelamine, and (+)-norchelidonine are described. Our rapid and convergent route to this class of natural products involved the development and application of a Pd II-catalyzed asymmetric ring-opening reaction of a meso-azabicyclic alkene with an aryl boronic acid as the key step. By screening a variety of functionalized ortho-substituted aryl boronic acids, chiral ligands and reaction conditions we were able to prepare the requisite cis-1-amino-2-aryldihydronaphthalenes in high yield and in up to 90 % ee. Early attempts to complete the synthesis of (+)-homochelidonine using an N-Boc azabicyclic alkene are described in full. The successful route required a protecting group alteration followed by B ring formation and then stereoselective installation of the C-11 syn-hydroxy group by regioselective epoxide ring-opening using a hydride source. Ring-opening of the same epoxide intermediate with water ultimately led to the synthesis of (+)-chelamidine. The same strategy was then used to synthesize the other structurally similar B/C hexahydrobenzo[c]phenanthridine alkaloids, (+)-chelidonine, (+)-chelamidine, and (+)-norchelidonine. 相似文献
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110.
Katarína Mosnáčková Alena Šišková Ivica Janigová Jozef Kollár Miroslav Šlosár Štefan Chmela Pavol Alexy Ivan Chodák Ján Bočkaj Jaroslav Mosnáček 《Chemical Papers》2016,70(9):1268-1278
The paper is aimed on the investigation of natural ageing of plasticized poly(lactic acid)/poly(β-hydroxybutyrate) PLA/PHB blend films during their one-season application as mulches under real field conditions in the western part of Slovakia. Acetyl tributyl citrate (ATBC) was used as the plasticizer. The analysis was performed on three differently exposed parts of the foil: i) buried in soil, ii) exposed to sunlight, and iii) shadowed by plants. In parallel, UV irradiation of the blend under laboratory controlled conditions (constant temperature of 30°C and relative humidity of 55 %) was carried out. The degradation effect was followed by changes in the molar mass, chemical and crystalline structures, as well as in thermal and mechanical properties. The ternary PLA/PHB/ATBC blend lost its tensile properties faster when buried in soil than when exposed to sunlight. This result is in agreement with the data obtained for the UV-irradiated materials. Young’s modulus values showed a significant mechanical degradation under the UV irradiation as well as during natural ageing. The study was also focused on the influence of mulches on the yield and quality of sweet pepper production, characterized by carotenoids and vitamin C content. 相似文献