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排序方式: 共有235条查询结果,搜索用时 15 毫秒
41.
Construction of Hexahydropyrido[3,2‐c]carbazole and Hexahydropyrrolo[3,2‐c]carbazole Skeletons for the Synthesis of Related Indole Alkaloids 下载免费PDF全文
Synthesis of tetracyclic hexahydropyrido[3,2‐c]carbazoles ( 9a and 9b ) and hexahydropyrrolo[3,2‐c]carbazoles ( 13a and 13b ) structures was achieved via a new synthetic approach for the synthesis of related indole alkaloids such as deethylaspidospermidine and deethylibophyllidine. Hexahydropyrrolo[3,2‐c]carbazole structure was constructed for the first time starting from ethyl 4‐oxo‐cyclohexanecarboxylate in seven steps. Some tetrahydrocarbazole derivatives ( 4 , 5 , 6 , 7 , 11 , and 12 ) were also synthesized. 相似文献
42.
The title compound, 1-(naphthalene-2-yl)-2-(1H-pyrazol-1-yl)ethanone O-butyl oxime, I, was synthesized. The crystal and molecular structures of I were determined by IR, 1H-NMR, mass spectrum, elemental analysis and X-ray single crystal diffraction. Molecular geometry from X-ray experiment of I in the ground state was compared using the Density Functional Theory (DFT) with B3LYP/6-311G(d,p) basis set. In addition, DFT calculation, molecular electrostatic potentials (MEP) and frontier molecular orbitals of I were performed at the B3LYP/6-311G(d,p) level of the theory. 相似文献
43.
44.
Yunus Bekdemir Halil Kutuk Sibel Celik John G. Tillett 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):973-980
The acid catalysed hydrolysis of some cyclic sulfamates, X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides ( 1a , X = Me; 1b , X = H; 1c , X = Cl; 1d , X = NO 2 ) have been studied in concentrated aqueous sulfuric and perchloric acid solutions. Analysis of the data by the Excess Acidity Method, activation parameters, substituent, solvent deuterium isotope effect and order of the catalytic effects of the acids are all in agreement with an A-1 mechanism in the studied range. 相似文献
45.
Sibel Topuz Buket Alpertunga 《International journal of environmental analytical chemistry》2013,93(9):787-795
A rapid and selective method for the simultaneous determination of triazine herbicides (atrazine, its degradation product desethylatrazine, simazine, prometryn, terbutryn) and N-methylcarbamate insecticides (propoxur, carbaryl and methiocarb) in surface water has been developed. A 0.5 L of the water sample was preconcentrated by passage through a 1 g C18 solid-phase extraction cartridge. The retained compounds were eluted with 5 mL of methanol from the cartridge. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV diode-array detection. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C18 column. Prometryn and terbutryn were determined at 240 nm; propoxur, methiocarb at 204 nm and the others at 220 nm. Recoveries varied from 85 to 102% over concentrations at 0.025 and 0.2 µg L?1. The limits of detection for the compounds investigated are in the range of 0.005-0.012 µg L?1. 相似文献
46.
A selective dopamine determination using a nafion-coated clinoptilolite-modified carbon paste electrode in the presence of
ascorbic acid was studied. Both cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) were used
for measurements of dopamine. To improve the selectivity of the clinoptilolite-modified carbon paste electrode in presence
of a high concentration of ascorbic acid, the electrode surface was coated with nafion membrane. Experimental parameters affecting
the determination of dopamine, including the clinoptilolite ratio, nafion membrane thickness, preconcentration time, preconcentration
solution pH, stripping solution pH and interferences are discussed. The developed sensor has a wide linear range, a low detection
limit, and good stability and reproducibility. The sensor offers a good alternative to existing analytical methods for dopamine,
permits a relatively short analysis time, and is simple, selective and inexpensive. 相似文献
47.
The effect of fermentation (retting) time and harvest time on kudzu (Pueraria lobata) fiber strength
Uludag Sibel Loha Veara Prokop Ales Tanner Robert D. 《Applied biochemistry and biotechnology》1996,57(1):75-84
Applied Biochemistry and Biotechnology - The noncommercial kudzu plant has been growing wild in the southern United States since the 1930s. In this article, the kudzu fibrous vine is investigated... 相似文献
48.
Chemisorption of thiol‐functionalized metallocene molecules on Si(111)‐ Ag√3×√3 surface: A density functional theory study 下载免费PDF全文
Herein, chemical adsorption properties of the thiol‐functionalized metallocene molecules [M(C5H4SH)2] on Si(111)‐Ag√3×√3 surface were investigated using density functional theory calculation. For this purpose, thiol‐modified ferrocene [Fe(C5H4SH)2], osmocene [Os(C5H4SH)2], and ruthenocene [Ru(C5H4SH)2] molecules were attached on the surface via two different binding models. The more favorable chemical binding energies of [Fe(C5H4SH)2], [Os(C5H4SH)2], and [Ru(C5H4SH)2] molecules were calculated as ?3.42, ?2.15, and ?2.00 eV, respectively. The results showed that the adsorption energies of metallocene molecules change independently by increasing the radius of metal ions where on going down the group of the periodic table. The calculated adsorption energies showed that [Fe(C5H4SH)2] molecule was more stable on the Si(111)‐Ag√3×√3 surface. By calculating the electronic band structure for metallocene/Si(111)‐Ag√3×√3 surfaces, we identified a flat dispersion band in a part of the surface Brillouin zone. © 2015 Wiley Periodicals, Inc. 相似文献
49.
Sibel Kasap Huseyin Tel Sabriye Piskin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):537-544
A spherical polyacrylonitrile–TiO2 composite adsorbent was prepared and its strontium removal potential was investigated. The Langmuir equation fixed well the
equilibrium data. The value of ∆H° = 8.943 kJ/mol and ∆G° = 6.291 kJ/mol at 298 K indicate that the adsorption of strontium onto TiO2/PAN composite adsorbent is an endothermic and non-spontaneous reaction. The kinetic process was described by a pseudo-second-order
rate model very well. 相似文献
50.