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891.
The synthesis of three stereoisomers of a major homologue of the methoxymycolic acids present in Mycobacterium tuberculosis is described. 相似文献
892.
Cobalt(II) bis(diphenylacetato)-bis(-picolinate) is synthesized and its geometrical and conformational isomers are investigated using dynamic NMR and molecular mechanics methods. The complex in the solution is shown to exist as cis and trans isomers, which are detected at 263 K in the course of a slow intermolecular ligand exchange. At T < 223 K, the intramolecular rotation of the phenyl radicals about the –O2C–CH(Ph)2 and –O2CCH(Ph)–Ph bonds slows, which results in the formation of different conformers. The energies of the retarded intermolecular exchange and of the retarded rotation of the phenyl radicals were calculated from 1H NMR and molecular mechanics data. 相似文献
893.
The synthesis of first‐ and second‐generation dendrons with defined ratios of orthogonally protected amine groups in the periphery ((benzyloxy)carbonyl (Cbz) and (tert‐butoxy)carbonyl (Boc) protection) and the degree to which they can be selectively removed are described. The reaction conditions required for these deprotections were applied to methacrylic acid (= 2‐methylprop‐2‐enoic acid) based dendronized polymers carrying the same peripheral protecting groups to investigate whether they have any detrimental interference with the polymer skeleton. Specifically it was explored whether dendrons attached to the backbone could possibly be cleaved off as a whole (de‐dendronization). Finally it was investigated how de‐dendronizations can be used for quantifying both the dendron‐structure perfection and the polymer‐backbone configurations. 相似文献
894.
Dimukhametov M. N. Bayandina E. V. Davydova E. Yu. Zyablikova T. A. Dobrynin A. B. Litvinov I. A. Al"fonsov V. A. 《Russian Chemical Bulletin》2001,50(12):2468-2470
The reaction of R-(+)-2-benzylideneaminobutan-1-ol with ethylene phosphorochloridite afforded phosphorus-epimeric (3R,5R)-2-(2-chloroethoxy)-5-ethyl-2-oxo-3-phenyl-1,4,2-oxazaphosphorinanes. The phosphorinane-ring closure proceeded stereospecifically and occurred only from one of the diastereofacial sides (re) of the C=N bond. 相似文献
895.
Shengfu Yang Hong Wu Qiquan Luo Aula M. Al Hindawi Berlian Sitorus Andrew M. Ellis Jinlong Yang 《Chemical science》2020,11(32):8502
We report that Au atoms within van der Waals complexes serve as catalysts for the first time. This was observed in ionization-induced chemistry of 1,6-hexanediol–Au and 1,8-octanediol–Au complexes formed in superfluid helium nanodroplets, where the addition of Au atom(s) made C2H4+ the sole prominent product in dissociative reactions. Density functional theory (DFT) calculations showed that the Au atom significantly strengthens all of the C–C bonds and weakens the C–O bonds in the meantime, making the C–C bonds stronger than the two C–O bonds in the ionized complexes. This leads to a preferential cleavage of the C–O bonds and thus a strong catalytic effect of the Au atoms in the reactions.Single Au atoms within van der Waals complexes are found to serve as catalysts in ionisation-induced chemistry for the first time. 相似文献
896.
Determination of albumin in biological fluids by flow injection analysis using the peroxyoxalate chemiluminescent system in micellar medium 总被引:2,自引:0,他引:2
A novel chemiluminescence (CL) method for the determination of papaverine (PAP) has been developed by combining the flow injection technique and its sensitizing effect on the weak CL reaction between sulfite and acidic permanganate. A mechanism for the CL reaction has been proposed on the basis of fluorescent and chemiluminescence spectra. The CL response is proportional to the concentration of PAP over the range 0.2-10 micro mol L(-1). The detection limit of PAP is 0.10 micro mol L(-1) (3 s) with a relative standard deviation (RSD) of 2.0% for 10 repetitive determinations of 1.0 micro mol L(-1) PAP. Interferences from other alkaloids in the opium, such as morphine and codeine, are negligible except that of narcotine. The method has been satisfactorily used for the determination of PAP in injections and compound liquorice tablets. 相似文献
897.
M. Žemberyová Abdo Al Hakem Zwaik I. Farkašovská 《Journal of Radioanalytical and Nuclear Chemistry》1998,229(1-2):67-71
The five step sequential extraction for speciation of copper and nickel originally designed for sediments has been applied
to soil samples. The extractant solutions were: 1 mol/l ammonium acetate, 1 mol/l hydroxylammonium chloride in 25% acetic
acid (1∶1), 0.1 mol/l hydrochlorid acid, 0.5 mol/l sodium hydroxide and 8 mol/l nitric acid. The residue was decomposed by
HF and HNO3. Using this procedure the metal fraction bound to the organic matter can be distinguished. The concentrations of analytes
were determined in the soil extracts by FAAS and ETAAS. Accuracy was assessed by comparing the sum of the contents of copper
and nickel in soil extracts with the total certified values of CRMs of soils. The overall recovery values for nickel was 84–105%
and for copper 105–114%. 相似文献
898.
Etor San Román Alan Vitrey Jerónimo Buencuerpo Iván Fernández Iván Prieto Benito Alén Antonio García‐Martín José M. Llorens S. R. J. Brueck José M. Ripalda 《固体物理学:研究快报》2016,10(2):164-167
We demonstrate high optical transmission in solar cell contacts based on nanowire arrays with subwavelength spacing. The photocurrent results obtained from fabricated devices are compared with numerical simulations. The proposed contact design leads to optical losses significantly smaller than the fraction of the top surface taken up by the metallic contact (<10% vs. 36%). The resulting sheet resistance of the contact is 46.7 Ω/square, comparing favourably with transparent conductive oxides.
899.
Solution properties of phenothiazine drug promazine hydrochloride with cationic hydrotropes in aqueous/electrolyte solution at different temperature 下载免费PDF全文
Malik Abdul Rub Naved Azum Abdullah M. Asiri Mohie E. M. Zayed Abdulrahman O. Al‐Youbi 《Journal of Physical Organic Chemistry》2016,29(9):476-489
The current work deals with the mixed micellization phenomena of surface active promazine hydrochloride (PMZ) drug with cationic hydrotropes (para‐toluidine hydrochloride and ortho‐toluidine hydrochloride) in absence and occurrence of 50 mmol kg?1 NaCl at five different temperature (293.15–313.15 K). PMZ is an amphiphilic phenothiazine drug and employed for the cure of mania and schizophrenia. Conductometry measurement was employed to gain a detailed picture of the interactions between drug and hydrotrope molecules. The experimental data were analyzed according to different mixing models within the outline of the pseudophase separation model. The evaluated values of critical micelle concentration (cmc) were found to be inferior than cmcid values signifying attractive interactions involving the both components in the solutions. NaCl further reduces the cmc of pure amphiphiles and their mixed systems as a result of screening of the electrostatic repulsion between the polar head groups. The micellar mole fractions (X1) of hydrotropes evaluated by various proposed models were constantly more than ideal values ( ) signifying high involvements of hydrotrope in mixed micelles. Activity coefficients ( and ) were always below one in all cases signifying synergism in mixed micelles. Thermodynamic parameters favor the process of micellization which is found to be entropy driven. The negative values of free energies of mixing demonstrated the stability of the mixed systems of drug and hydrotrope. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
900.
Qamar J. A. Khan Mohamed Al‐Lawatia Fatma A. Al‐Kharousi 《Mathematical Methods in the Applied Sciences》2016,39(10):2647-2658
A theoretical eco‐epidemiological model of a prey–predator interaction system with disease in prey species is studied. Predator consumes both susceptible and infected prey population, but predator also feeds preferentially on many numerous species, which are over represented in the predator's diet. Equilibrium points of the system are determined, and the dynamic behaviour of the system is investigated around equilibrium points. Death rate of predator species is considered as a bifurcation parameter to examine the occurrence of Hopf bifurcation in the neighbourhood of the coexisting equilibria. Numerical simulations are carried out to support the analytical results. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献