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41.
An efficient and simple catalytic method for the isomerization of readily prepared allylic alcohols is described. We focus particularly on cyclic examples and the synthesis of unusual enyne and dienols. The benzoic acid catalysts employed are commercially available and very inexpensive and can be tuned for reactivity and substrate sensitivity. 相似文献
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Sadler JE Szumski DS Kierzkowska A Catarelli SR Stella K Nichols RJ Fonticelli MH Benitez G Blum B Salvarezza RC Schwarzacher W 《Physical chemistry chemical physics : PCCP》2011,13(40):17987-17993
A new in situ electrochemical method of functionalizing an oxide-free Ni surface is demonstrated using octanethiol. Initial adsorption results in a multilayer molecular film, which blocks both the hydrogen evolution reaction (HER) and re-oxidation of the Ni by ambient oxygen. However, excess octanethiol can be removed by rinsing with ethanol, leaving behind a monolayer that continues to protect against re-oxidation but gives rise to an unexpected enhancement in the HER, with a greater enhancement for longer film formation times. The presence of an octanethiol monolayer on the surface was confirmed by spectroscopic observation of the CH(2), CH(3) and thiolate groups using infra red spectroscopy, while X-ray photo-electron spectroscopy demonstrated the effectiveness of the thiol layer as a barrier to surface oxidation. The electrochemically prepared octanethiol film impedes oxidation of the Ni in air more effectively than a film formed by immersion in a solution of octanethiol in ethanol. 相似文献
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Nitration of estrone has been investigated with different types of metal salts in the presence of solid surfaces under various conditions. 相似文献
46.
Jinmei Du Samantha Shintay Xiangwu Zhang 《Journal of Polymer Science.Polymer Physics》2008,46(15):1611-1618
Electrospinning is the process of producing ultrafine fibers by overcoming the surface tension of a polymer solution using high voltage. In this work, the effects of both solution properties (viscosity, conductivity, and surface tension) and operational conditions (voltage, feed rate, and spinneret‐collector distance), on the structure of electrospun polyacrylonitrile nanofibers, were systematically investigated. Iron acetylacetonate was added to the electrospinning solution to control fiber diameter by selectively adjusting solution properties. It was found that, with increased salt concentration, the fiber diameter increases and then passes through a maximum due to changes in solution viscosity, conductivity, and surface tension. In addition, the fiber diameter increases with increase in voltage, feed rate, and spinneret‐collector distance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1611–1618, 2008 相似文献
47.
Ebejer KA Brereton RG Carter JF Ollerton SL Sleeman R 《Rapid communications in mass spectrometry : RCM》2005,19(15):2137-2143
A procedure is described for the determination of the distribution of the contamination of banknotes with controlled drugs using tandem mass spectrometry. The method is illustrated using diacetylmorphine, which is the major active component of heroin. A series of banknotes is introduced into the mass spectrometer and the intensities of two product ions (m/z 328 and 268) derived from the precursor protonated molecule (m/z 370) are recorded. A banknote is considered contaminated if it shows a significant peak for both product ions, and if the ratio of intensities of these two peaks falls within accepted limits. The distribution of diacetylmorphine on sterling banknotes taken from general circulation within the UK can be modelled by an arcsin (square root) transformation of the data or by a log transformation of the data with a higher proportion of contamination. The two models were found to be in close agreement, predicting an upper limit (at 99.9% confidence) of contamination on banknotes from general circulation between 9 and 10%. The percentage contamination in a case study was calculated and compared to the background distribution using the two models proposed. This comparison revealed that the contamination present in the case study was inconsistent with that present on banknotes in general circulation. 相似文献
48.
Marshall LJ Williams JR Almond MJ Atkinson SD Cook SR Matthews W Mortimore JL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):233-241
Three ochre samples (A (orange-red in colour), B (red) and C (purple)) from Clearwell Caves, (Gloucestershire, UK) have been examined using an integrated analytical methodology based on the techniques of IR and diffuse reflectance UV-visible-NIR spectroscopy, X-ray diffraction, elemental analysis by ICP-AES and particle size analysis. It is shown that the chromophore in each case is haematite. The differences in colour may be accounted for by (i) different mineralogical and chemical composition in the case of the orange ochre, where higher levels of dolomite and copper are seen and (ii) an unusual particle size distribution in the case of the purple ochre. When the purple ochre was ground to give the same particle size distribution as the red ochre then the colours of the two samples became indistinguishable. An analysis has now been completed of a range of ochre samples with colours from yellow to purple from the important site of Clearwell Caves. 相似文献
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The following copper(I) and silver(I) complexes of 2-amino-1,3,4-thiadiazole (atz) and 2-ethylamino-1,3,4-thiadiazole (eatz) have been prepared and studied by conductometric, IR and Raman methods: CuXL(X = Cl, Br, I; L = atz, eatz), CuXL3(X = ClO4, NO3; L = atz, eatz), AgClO4·1.5atz·1/3 EtOH, AgNO3·2.5atz, AgClO4·3eatz, AgNO3·eatz. The ligands are bonded through the amine nitrogen atoms with ν(MN) bands in the 520–410 cm?1 region. The CuXL complexes have a trigonal (N, 2Xb) coordination with a probable weaker axial interaction. The CuXL3 and AgCIO4·3eatz complexes probably have a trigonal pyramidal (3N,O) coordination. In the atz complexes of silver perchlorate and nitrate some ligand molecules are bridging. The AgNO3·2.5atz complex is likely to have a dimeric structure with tetrahedral coordination of the silver ion. 相似文献