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991.
Vapor generation-inductively coupled plasma-optical emission spectrometry was used for the determination of sulfide in water samples preserved by the addition of a zinc acetate and sodium hydroxide solution. Hydrogen sulfide and acid-volatile sulfides were transformed, by acidification, to a gaseous phase in a vapor generator and subsequently detected by inductively coupled plasma optical emission spectrometry. Compounds interfering with iodometric titration and spectrophotometric determination were examined as potential chemical interferents. The proposed method provides results comparable to iodometric titration in the tested concentration range 0.06-22.0 mg L−1. Limit of detection for the determination of hydrogen sulfide by this method is 0.03 mg L−1. 相似文献
992.
Two trisaccharides as new sulfonic acid mimetics of the sialyl Lewis A tetrasaccharide were synthesized. The natural sialic acid residue is replaced by a C-sulfonic acid moiety attached to position C-3′ of the lactosamine unit of the mimetics. The l-fucose unit was also replaced by a d-arabinose ring in one of the analogues. Formation of the sulfonic acid moiety on the trisaccharide level could be successfully achieved by means of introduction of an acetylthio moiety into the galactose skeleton and subsequent oxidation. The equatorial arrangement of the acetylthio group linked to C-3 of the galactose ring could be achieved by double nucleophilic substitution; efficient formation of the gulo-triflate derivatives required low-power microwave activation. Oxidation of the acetylthio group was carried out using Oxone in acetic acid. 相似文献
993.
A novel tandem one-pot method for the synthesis of α-aminomethylene-γ-butyrolactone derivatives has been developed through the regioselective epoxide opening reactions with the Blaise reaction intermediates, generated by the reaction of a Reformatsky reagent with nitriles. Formation of a modified Blaise reaction intermediate by the addition of a stoichiometric amount of n-BuLi followed by slow addition of epoxide is required for the good yield of γ-butyrolactones. 相似文献
994.
Ko YJ Shakya A Wang H Grubisic A Zheng W Götz M Ganteför G Bowen KH Jena P Kiran B 《The Journal of chemical physics》2010,133(12):124308
The equilibrium structure, stability, and electronic properties of the Al(13)X (X=H,Au,Li,Na,K,Rb,Cs) clusters have been studied using a combination of photoelectron spectroscopy experiment and density functional theory. All these clusters constitute 40 electron systems with 39 electrons contributed by the 13 Al atoms and 1 electron contributed by each of the X (X=H,Au,Li,Na,K,Rb,Cs) atom. A systematic study allows us to investigate whether all electrons contributed by the X atoms are alike and whether the structure, stability, and properties of all the magic clusters are similar. Furthermore, quantitative agreement between the calculated and the measured electron affinities and vertical detachment energies enable us to identify the ground state geometries of these clusters both in neutral and anionic configurations. 相似文献
995.
Zdeněk Trávníček Prof. Dr. Richard Pastorek Pavel Štarha Igor Popa Václav Slovák 《无机化学与普通化学杂志》2010,636(8):1557-1564
The nickel(II) N‐benzyl‐N‐methyldithiocarbamato (BzMedtc) complexes [Ni(BzMedtc)(PPh3)Cl] ( 1 ), [Ni(BzMedtc)(PPh3)Br] ( 2 ), [Ni(BzMedtc)(PPh3)I] ( 3 ), and [Ni(BzMedtc)(PPh3)(NCS)] ( 4 ) were synthesized using the reaction of [Ni(BzMedtc)2] and [NiX2(PPh3)2] (X = Cl, Br, I and NCS). Subsequently, complex 1 was used for the preparation of [Ni(BzMedtc)(PPh3)2]ClO4 ( 5 ), [Ni(BzMedtc)(PPh3)2]BPh4 ( 6 ), and [Ni(BzMedtc)(PPh3)2]PF6 ( 7 ). The obtained complexes 1 – 7 were characterized by elemental analysis, thermal analysis and spectroscopic methods (IR, UV/Vis, 31P{1H} NMR). The results of the magnetochemical and molar conductivity measurements proved the complexes as diamagnetic non‐electrolytes ( 1 – 4 ) or 1:1 electrolytes ( 5 – 7 ). The molecular structures of 4 and 5· H2O were determined by a single‐crystal X‐ray analysis. In all cases, the NiII atom is tetracoordinated in a distorted square‐planar arrangement with the S2PX, and S2P2 donor set, respectively. The catalytic influence of selected complexes 1 , 3 , 5 , and 6 on graphite oxidation was studied. The results clearly indicated that the presence of the products of thermal degradation processes of the mentioned complexes has impact on the course of graphite oxidation. A decrease in the oxidation start temperatures by about 60–100 °C was observed in the cases of all the tested complexes in comparison with pure graphite. 相似文献
996.
Emanuel Makrlík Petr Vaňura Jan Budka Pavel Selucky 《Monatshefte für Chemie / Chemical Monthly》2010,287(3):31-33
Abstract
From extraction experiments in the two-phase water–nitrobenzene system and γ-activity measurements, the stability constants of the tetraethyl p-tert-butyltetrathiacalix[4]arene tetraacetate (cone)·M+ complexes (M+ = Li+, H3O+, NH4 +, Ag+, or K+) were determined in water-saturated nitrobenzene. It was found that these constants increase in the cation order NH4 + < K+ < H3O+ < Ag+ < Li+ < Na+. 相似文献997.
Tomá? Gucky Eva ?ezní?ková Petr D?ubák Marián Hajdúch Vladimír Kry?tof 《Monatshefte für Chemie / Chemical Monthly》2010,55(7):709-714
Abstract
The deregulation of cell cycle components in cancer cells has provided a rationale for the development of small molecule inhibitors of cyclin-dependent kinases as novel anticancer drugs. A series of 1,5-diaryl-3-(3,4,5-trihydroxyphenyl)-1H-pyrazolo[4,3-e][1,2,4]triazines was synthesized and their kinase inhibitory activity and cytotoxicity against several cancer cell lines has been evaluated. Some of the compounds of the series exhibited induction of caspase-dependent cell death and inhibition of cyclin-dependent kinase 2 (CDK2). 相似文献998.
Emanuel Makrlík Ji?í Dybal Ji?ina ?vor?íková Jan Budka Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2010,287(1):507-510
Abstract
From extraction experiments in the two-phase water/nitrobenzene system, the stability constant of the silver ionophore IV (i.e., 5,11,17,23-tetra-tert-butyl-25,27-bis[2-(methylthio)ethoxy]calix[4]arene)–Ag+ complex in nitrobenzene saturated with water was determined. Furthermore, the most probable structure of the resulting complex was derived by means of density functional level of theory calculations. 相似文献999.
1000.
Imre Miklós Szilágyi Andrea Deák Csaba Várhelyi Jr. János Madarász György Pokol Ágnes Gömöry Csaba Várhelyi 《Polyhedron》2010
Two new cobalt(III)-chelates, trans-bis(methyl-ethyl-dioximato)-chloro-β-picoline-cobalt (III) (1), and trans-bis(methyl-ethyl-dioximato)-chloro-3,4-lutidine-cobalt (III) (2) were obtained by oxidizing a mixture of CoCl2, methyl-ethyl-dioxime and amines: β-picoline (3-methyl-pyridine) for (1) and 3,4-lutidine (3,4-dimethyl-pyridine) for (2). The crystal structure of (1) was determined by single crystal XRD (monoclinic, space group P21/c (No. 14) with a = 8.391(3) Å, b = 14.421(5) Å, c = 18.383(8) Å, β = 114.57(2)°, R = 0.0499), while both (1) and (2) were studied by middle and far FTIR spectroscopy, electrospray ionization (ESI) MS, powder XRD and thermal analysis (TG/DTA-MS). Melting of the related complexes 1 and 2 at 219 and 184 °C, respectively, results in an immediate chemical degradation of their whole structure and tarring of ligands. 相似文献