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51.
The stoichiometry of the reaction between ferrocyanide and thorium, neodymium, uranyl ion and mercury(II) has been investigated. The first three give single products irrespective of the order of addition of the reagents, but the last does not. If mercury(II) is added to ferrocyanide Hg(2)Fe(CN)(6) is obtained, but if ferrocyanide is added to mercury(II) various cyanide complexes of mercury are formed. The K(sp) values for the precipitates are reported. 相似文献
52.
Selzer Y Cabassi MA Mayer TS Allara DL 《Journal of the American Chemical Society》2004,126(13):4052-4053
We report temperature dependence measurements on the conductance of individual molecular wires. The results show for the first time in a molecular junction the theoretically predicted transition from coherent superexchange tunneling conductance to an activated hopping mechanism as temperature is increased. 相似文献
53.
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55.
8-Quinolinol (oxine) and 2-(2-(5 chloropyridylazo)-5-dimethylamino)-phenol (5ClDMPAP) were immobilized on the non ionic sorbents Amberlite XAD-4 and XAD-7. These loaded resins were used for the preconcentration of Ce, La and Pr. High preconcentration factors were obtained in each case. After the retention of these rare earths, the resins were measured as thin films by x-ray fluorescence spectrometry. Up to 50 ppm of REEs can be retained on these thin films. 相似文献
56.
Sameer Chavda Elliot Coulbeck Gregory S. Coumbarides Marco Dingjan Jason Eames Stephanos Ghilagaber Yonas Yohannes 《Tetrahedron: Asymmetry》2006,17(24):3386-3399
The resolution of 2-phenylpropanoyl chloride using an equimolar combination of quasi-enantiomeric oxazolidinones is discussed. The levels of diastereoselectivity were found to be dependent upon the structural nature of the metallated oxazolidinone, temperature and metal counter-ion. 相似文献
57.
Starting from earlier work by Baudler we introduce a chemical heuristic for the systematic deduction and classification of covalent partial structures of phosphorus in polycyclic phosphanes, phosphorus-rich polycyclic phosphides, and allotropes of phosphorus except the black forms. This approach is used to direct ab initio techniques (which also confirm the rules) in the quest for as yet unknown forms of molecular or macromolecular phosphorus. Based on calculated stabilities of systematically generated structural alternatives we rationalize the stabilities of Hittorf's phosphorus and of molecular P4, confirm the possible existence of at least one other crystalline allotropic form of phosphorus, and provide insight into the probable structure of amorphous red phosphorus. In total, the combined approach of chemical heuristics and large scale ab initio calculations presented in this work supplies a coherent chemical understanding of covalent polyphosphorus structures. 相似文献
58.
A new sensitive and selective preconcentration-fluorimetric method for determination of terazosin based on its native fluorescence was developed. The analyte, initially present in aqueous matrix, was treated with an extractive non-ionic surfactant solution and separated by the clouding phenomenon. The optimum analytical conditions for terazosin assay were established. Under these conditions, linear calibration curves were obtained over the range of 1 × 10−5 to 7.0 μg mL−1 with detection and quantification limits of 1.11 × 10−5 and 3.7 × 10−5 μg mL−1, respectively. Additionally, the binding constant (KB) for the terazosin-PONPE 7.5 system was determined given a value of 1028 L mol−1. The developed coupled methodology, which thoroughly satisfies the typical requirements for pharmaceutical control processes, was proved to be appropriate for monitoring terazosin in actual pharmaceutical formulations and biological fluid sample. The results were validated by recovery test and by comparison with other reported methods, being highly satisfactory. 相似文献
59.
Jos L. Marco 《Journal of heterocyclic chemistry》1986,23(1):287-288
From (S)-pyroglutamic acid ( 1 ) the asymmetric synthesis of (S)-5-ethyl-2-pyrrolidinone ( 5 ) in 30% yield is described. 相似文献
60.
The reactions of perfluoroalkyl- and perfluoroacyl-iminosulfur difluorides with chlorine monofluoride result in the preparation of perfluoroalkyldichloroamines and a new class of compounds N,N-dichloroperfluoroamides, RfC(O)NCl2, via the elimination of SF4. The amides, FC(O)NCl2 and CF3C(O)NCl2, in addition to 1,2-bis-(dichloroamino)tetrafluoroethane, Cl2NCF2CF2NCl2, are reported and characterized. The reactions of CIF with other sulfur(IV) imines proceed in an analogous manner to form perfluoroalkyl-dichloroamines via the elimination of the corresponding sulfur(IV) fluoride. 相似文献