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21.
S. S. Ismail 《Journal of Radioanalytical and Nuclear Chemistry》1993,169(2):381-395
Different pattern recognition techniques were applied for classification and characterization of a large number of coal, and coal fly ash samples. Cluster analysis was performed on 116 samples using the concentration data of 40 elements. The effect of the number and type of the elements on the clustering was studied in detail. It was proved that short time activation analysis enables the characterization of these types of samples if139Ba and87Sr are included, these data being obtained by increasing the irradiation and counting times. The two elements and chlorine were found to be necessary for such a classification. The combination between cluster analyses and principal component analysis gives accurate and confirmed results. The statistical analyses of the subgroups are compared. 相似文献
22.
A rotating disk-ring electrode was used for study of a series of organomercury compounds R2Hg, where R = CN, CF(NO2)2, C6F5, PhCC, p-NO2C6H4OCC, PhSCH2CC, PhCOCH2, CH2CN, CCl2CCl, 2-phenyl-o-carboranyl. Reduction of these compounds at a Pt-disk in acetonitrile is a two-electron process and results in generation of the carbanion R?. The carbanions generated at the disk interact with the solvent during their convective diffusion to the ring electrode where there may be oxidized. The main reaction in solution, shown using chromatography-mass spectrometry techniques, is acid-base interaction of carbanions with the solvent acetonitrile, which acts as a Brönsted acid. Reaching the ring, the carbanions may be oxidized at anodic potentials of the ring; oxidation potentials depend significantly on carbanion structure (e.g.+0.28 V (vs. SCE), for PhCC? and +2.20 V for CN?. It is shown that PKa value of the carbanions do not correlate with the oxidation potentials, however, a linear correlation is observed between pKa values and a special parameter called the efficiency coefficient. 相似文献
23.
Cetinkaya B Demir S Ozdemir I Toupet L Sémeril D Bruneau C Dixneuf PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2323-2330
The reaction of electron-rich carbene-precursor olefins containing two imidazolinylidene moieties [(2,4,6-Me(3)C(6)H(2)CH(2))NCH(2)CH(2)N(R)Cdbond;](2) (2a: R=CH(2)CH(2)OMe, 2 b R=CH(2)Mes), bearing at least one 2,4,6-trimethylbenzyl (R=CH(2)Mes) group on the nitrogen atom, with [RuCl(2)(arene)](2) (arene=p-cymene, hexamethylbenzene) selectively leads to two types of complexes. The cleavage of the chloride bridges occurs first to yield the expected (carbene) (arene)ruthenium(II) complex 3. Then a further arene displacement reaction takes place to give the chelated eta(6)-mesityl,eta(1)-carbene-ruthenium complexes 4 and 5. An analogous eta(6)-arene,eta(1)-carbene complex with a benzimidazole frame 6 was isolated from an in situ reaction between [RuCl(2)(p-cymene)](2), the corresponding benzimidazolium salt and cesium carbonate. On heating, the RuCl(2)(imidazolinylidene) (p-cymene) complex 8, with p-methoxybenzyl pendent groups attached to the N atoms, leads to intramolecular p-cymene displacement and to the chelated eta(6)-arene,eta(1)-carbene complex 9. On reaction with AgOTf and the propargylic alcohol HCtbond;CCPh(2)OH, compounds 4-6 were transformed into the corresponding ruthenium allenylidene intermediates (4-->10, 5-->11, 6-->12). The in situ generated intermediates 10-12 were found to be active and selective catalysts for ring-closing metathesis (RCM) or cycloisomerisation reactions depending on the nature of the 1,6-dienes. Two complexes [RuCl(2)[eta(1)-CN(CH(2)C(6)H(2)Me(3)-2,4,6)CH(2)CH(2)N- (CH(2)CH(2)OMe)](C(6)Me(6))] 3 with a monodentate carbene ligand and [RuCl(2)[eta(1)-CN[CH(2)(eta(6)-C(6)H(2)Me(3)-2,4,6)]CH(2)CH(2)N-(CH(2)C(6)H(2)Me(3)-2,4,6)]] 5 with a chelating carbene-arene ligand were characterised by X-ray crystallography. 相似文献
24.
3-[1′(1′H)-Substituent-pyrazol-5′-yl]benzo[5,6]coumarins and 3-(1′,2′-oxazol-5′-yl)benzo[5,6]coumarin were prepared via condensation of 3-(2′-formyl-1′-chlorovinyl)benzo[5,6] coumarin with hydrazine derivatives or hydroxylamine.Reaction of 3-[1′(1′H)-pyrazol-5′-yl]benzo[5,6]coumarin with alkyl halides,olefinic compunds or acid chlorides are described. 相似文献
25.
In order to obtain some 6,8‐diarylimidazo[1,2‐a]pyrazines, 1‐(2‐aryl‐2‐oxoethyl)‐2‐aryloylimidazole derivatives were reacted with ammonium acetate in acetic acid by using a new method different from that found in the literature. Anticancer activities of the compounds obtained were evaluated and the noticeable activity values were reported. 相似文献
26.
Ronald E. Banks Ismail M. Farhat Roy Fields Robin G. Pritchard Mohamad M. Saleh 《Journal of fluorine chemistry》1985,28(3):325-340
The nitrosoarenes ArNO (Ar = C6H5, 2-MeC6H4, 2,4,6- Me3C6H2 and C6F5) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds pyFN()Ar (pyF = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of pyFNNC6H2Me3-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound pyFN()C6F5. X-Ray methods have been used to determine the molecular geometry of pyFN()C6H2Me3-2,4,6. 相似文献
27.
J. Wilson Quail Nargis Ismail M. Soledade C. Pedras Susan M. Boyetchko 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):o268-o271
The crystal structures of pseudophomins A and B, with primary structures β‐hydroxydecanoyl–l ‐Leu–d ‐Glu–d ‐allo‐Thr–d ‐Ile–d ‐Leu–d ‐Ser–l ‐Leu–d ‐Ser–l ‐Ile monohydrate, C55H97N9O16·H2O, and β‐hydroxydodecanoyl–l ‐Leu–d ‐Glu–d ‐allo‐Thr–d ‐Ile–d ‐Leu–d ‐Ser–l ‐Leu–d ‐Ser–l ‐Ile monohydrate, C57H101N9O16·H2O, new cyclic lipodepsipeptides isolated from Pseudomonas fluorescens strain BRG100, have been solved. The absolute configuration of pseudophomin A has been determined from anomalous dispersion and the stereochemistry of the β‐hydroxy acid group is R. 相似文献
28.
Pseudo-first-order rate constants (kobs) for alkaline hydrolysis of 4-nitrophthalimide show a monotonic decrease with increase in [C12E23]T (total concentration of Brij 35) at constant [CH3CN] and [NaOH]. This micellar effect is explained in terms of a pseudophase micelle model. The rate of hydrolysis becomes too slow to monitor at [C12E23]T≥0.03 M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C12E23]T≥0.04 M in the presence of 0.006–0.02 M CTABr at 0.01 M NaOH. The plots of kobs versus [C12E23]T show minima at 0.006 and 0.01 M CTABr, while such a minimum is not visible at 0.02 M CTABr. 相似文献
29.
AbdElAziz A. Nayl Hamada Mohamed Ibrahim Kamal M. Dawood Wael A. A. Arafa Ahmed I. Abd-Elhamid Ismail M. Ahmed Mohamed A. Abdelgawad Hazim M. Ali Ibrahim Hotan Alsohaimi Ashraf A. Aly Stefan Brse Asmaa Kamal Mourad 《Molecules (Basel, Switzerland)》2022,27(19)
An appropriate and efficient Q-tube-assisted ammonium acetate-mediated protocol for the assembly of the hitherto unreported 5-arylazopyrazolo[3,4-b]pyridines was demonstrated. This methodology comprises the cyclocondensation reaction of 5-amino-2-phenyl-4H-pyrazol-3-one with an assortment of arylhydrazonals in an NH4OAc/AcOH buffer solution operating a Q-tube reactor. This versatile protocol exhibited several outstanding merits: easy work-up, mild conditions, scalability, broad substrate scope, safety (the Q-tube kit is simply for pressing and sealing), and a high atom economy. Consequently, performing such reactions under elevated pressures and utilizing the Q-tube reactor seemed preferable for achieving the required products in comparison to the conventional conditions. Diverse spectroscopic methods and X-ray single-crystal techniques were applied to confirm the proposed structure of the targeted compounds. 相似文献
30.
Mohammed Ahmed Ismail Alhasawi Mohammad Aatif Ghazala Muteeb Mir Waqas Alam Mohamed El Oirdi Mohd Farhan 《Molecules (Basel, Switzerland)》2022,27(21)
Turmeric spice contains curcuminoids, which are polyphenolic compounds found in the Curcuma longa plant’s rhizome. This class of molecules includes curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Using prostate cancer cell lines PC3, LNCaP, DU145, and C42B, we show that curcuminoids inhibit cell proliferation (measured by MTT assay) and induce apoptosis-like cell death (measured by DNA/histone ELISA). A copper chelator (neocuproine) and reactive oxygen species scavengers (thiourea for hydroxyl radical, superoxide dismutase for superoxide anion, and catalase for hydrogen peroxide) significantly inhibit this reaction, thus demonstrating that intracellular copper reacts with curcuminoids in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitize normal breast epithelial cells (MCF-10A) to curcumin-mediated growth inhibition, as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters CTR1 and ATP7A in MCF-10A cells, which is attenuated by the addition of curcumin in the medium. We propose that the copper-mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of curcuminoids. 相似文献