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941.
György Inzelt Roger W. Day James F. Kinstle James Q. Chambers 《Journal of Electroanalytical Chemistry》1984,161(1):147-161
Thin films of a tetracyanoquinodimethane (TCNQ) oligomer adsorbed on optically transparent platinum electrodes have been studied using spectroelectrochemical techniques. In contact with aqueous electrolytes the electron aceptor sites in these modified electrodes are reduced to mixtures of the radical aion, TCNQ?, the dimer radical anion, TCNQ2?2, the dimer dianion, TCNQ22?, and the dianion, TCNQ2∮. Electrolyte effects on the reduction process and the stability of the reduced films were studied. Both monovalent and divalent ions exhibited Nernstian potential dependence, and in the presence of Ca2+ ions the dianion state was stabilized. Counterion effects are suggested as the origin of variations in the wave shape in multcycle voltammograms. 相似文献
942.
The 1-C-nitroglycosyl chloride reacted with the anions form 2-nitropropane, nitromethane, and diethyl malonate, to give the chain-extended products 2 (81%), 5 (72%), and 6 (83%), respectively. Treatment of the 1-C -nitroglycosyl bromide 7 by the lithium salt obtained form 8 gave the dodecodiulose derivative 9 (76%). Th β-D-configuration of 2 and 9 was inferred form their NMR and CD spectra. Treatment of 2 and 9 with sodium sulfide gave the enol ethers 3 (96%) and 10 (92%), respectively. The (Z)-configuration of 10 was deduced form the configuration of its hydrogenation product 11 . 相似文献
943.
A recently proposed method of looking at sampling uncertainty has been tested by its application to the sampling and analysis of several types of food and an animal feedstuff. In this 'SAD' method, increments comprising the conventional sample (that is, collected in the fashion prescribed by the standard sampling protocol) are allocated to either of two equal sized 'splits', which are prepared and analysed separately. The absolute difference between the analytical results for the two splits (the split absolute difference, or SAD) is plotted on a one-sided control chart. A non-compliance indicates that the combined uncertainty of sampling or analysis is larger than expected and the result of the measurement (the mean of the two split results) is possibly not fit for purpose. In addition, the SAD results give rise to a rugged estimate the uncertainty associated with the sampling protocol, often a major part of the total measurement uncertainty. 相似文献
944.
945.
Alberto Roger Schibli Roger Angst Daniela Schubiger P. August Abram Ulrich Abram Sonja Kaden Th. A. 《Transition Metal Chemistry》1997,22(6):597-601
Transition Metal Chemistry - A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl?, Br?] is presented. The intermediates... 相似文献
946.
Near-infrared dyes are attractive as labeling reagents to enhance sensitivity in trace analysis largely because background fluorescence is low in this spectral region. Here we demonstrate, towards a goal of detecting DNA adducts in small biological samples, that some near-infrared (IR) dye-labeled deoxynucleotides can be separated and detected with high sensitivity by capillary electrophoresis (CE)-laser-induced fluorescence detection (LIF) in a realistic way (handling detection limit of 25 amol) for near-IR dye-labeled deoxynucleotides. This detection limit is achieved by polarity-switching injection of 2.0 microl from a volume of 5.0 microl, in which the compounds are 5 x 10(-12) mol/l in 50% aqueous methanol. Although the adenine and cytosine-containing conjugates co-migrated, the other three (guanine, N2-ethylguanine and thymine) were resolved. 相似文献
947.
Chattopadhyay Shyamal Kumar Mitra Kamala Biswas Subhendu Naskar Subhendu Mishra Dipankar Adhikary Bibhutosh Harrison Roger G. Cannon John F. 《Transition Metal Chemistry》2004,29(1):1-6
Reaction of 1-phenyl 5-(aminophenyl) 9-(2-pyridyl) benzimidazole derivatives (2) with cis-Ru(bpy)2Cl2 in MeCN results in the formation of N-(aryl) imidazo[1,5a] pyridine derivatives (4) and cis-[Ru(bpy)2(MeCN)2]2+
(5). Crystal structures of N-(4-chlorophenyl) imidazo[1,5a] pyridine (4b) and cis-[Ru(bpy)2(MeCN)2](ClO4)2
(5) are also reported. 相似文献
948.
Peter Lievens Peter Thoen Steven Bouckaert Wim Bouwen Erno Vandeweert Frederik Vanhoutte Horst Weidele Roger E. Silverans 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,42(3):231-235
We report on the production of small and medium size lithium and lithium oxide clusters by a laser vaporization cluster source. The isotopomeric distribution of natural lithium allowed to identify LikO clusters as the most abundant components in the mass spectrum. Photoionization efficiency curves of LikO clusters with photon energies from 3.4 to 4.7 eV were measured for 8 ≤ k ≤ 27. Using linear extrapolation of the increase in photoionization efficiency with photon energy, ionization potentials were extracted. With the chemical bond of the O2- anion to two Li atoms, leaving n = k-2 valence electrons in the (Li2O)Lin clusters, clear shell closure effects are present at n = 8 and n = 20. 相似文献
949.
Kinetics of adsorption of high molecular weight anionic polyacrylamide onto kaolinite: the flocculation process 总被引:4,自引:0,他引:4
The adsorption kinetics of anionic polyacrylamide flocculant onto kaolinite clay are examined as a function of flocculant dosage and pH. Special attention has been given to the flocculation effect during the adsorption process and the resulting inhibition of further adsorption. At pH 8.5 the adsorption capacity of anionic polyacrylamide on kaolinite is low while at pH 4.5, the adsorption capacity increases. Flocculant adsorption has been shown to be related to the amount of available surface area, pH, flocculant dosage, and the resulting floc strength, which controls the rate of new surface area exposure and hence the continuation of further adsorption. At both pH 4.5 and pH 8.5, complete adsorption is achieved at low flocculant dosages and adsorption equilibrium is achieved at high flocculant dosages after 1 day. In contrast, at intermediate flocculant dosages adsorption equilibrium is not reached over a 7-day period, due to a continuously increasing surface area. 相似文献
950.
The transformations of 12 bicyclo[2.2.2]oct-5-en-2-ols ( V or VI ) to 3-(cyclohex-3-enyl)-2-alkanones ( III or IV ), via β-cleavage of their potassium alkoxides in HMPA, has been investigated (cf. Table 1). As an illustration of this synthetic methodology, a stereoselective synthesis of (±)-trichodiene ((±)- 1 ) is described which involves the β-cleavage of the tricyclic potassium alkoxides 46a and 47a to cyclopentanone 4 (cf. Scheme 7). 相似文献