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Charles M. Lindsay Keith Smith Charles Allan Brown Kathleen Betterton-Cruz 《Tetrahedron letters》1984,25(9):995-998
Unsymmetrical hexathioorthooxalates of types () and () undergo elimination of dialkyl disulfide on heating in an organic solvent; the reaction, which is catalyzed by acid, proceeds without fission of the central C:C bond and provides the first general, high yield synthesis of unsymmetrical benzotetrathiafulvalenes of types () and (). 相似文献
35.
Michael I. Bruce Jennifer K. Walton Michael L. Williams Brian W. Skelton Allan H. White 《Journal of organometallic chemistry》1981,212(3):C35-C38
Contrary to some previously depicted structures, the proton in HC5(CO2Me)5 is bonded to two oxygens rather than to carbon; the lithium ion in Li[C5(CO2Me)5] (H2O) is tetrahedrally coordinated by two carbonyl oxygens from one C5 anion, one from a second anion, and a water molecule. 相似文献
36.
We examine the relative utility of the Landau-Zener, phase integral, and semiclassical Magnus approximations for processes involving a real crossing of two potential curves. As an example we consider rotational coupling in Na 2 + . Numerical calculations for the ¦3p〉→¦3s〉 quenching process and for ¦3p〉→¦3d〉 excitation agree well with recent experiments in the energy range 20 eV≦EK≦50 eV. Simple expressions forS-matrix elements, differential and total cross sections in these approximations depend only on accurate evaluation of a few JWKB phases. For the total cross section further simplification of the Magnus results yields a useful semiempirical formula. 相似文献
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V. W. Pike M. N. Eakins R. M. Allan A. P. Selwyn 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):291-297
Methods have been developed for the labelling of acetate and palmitic acid with the positron-emitting radionuclide,11C (T=20.4 min). Labelling was achieved via carbonation of the appropriate alkyl magnesium bromide (methyl magnesium bromide
or n-pentadecyl magnesium bromide) with11C-labelled carbon dioxide produced by the14N(p, α)11C nuclear reaction. The radiochemical yield and speed of each method of labelling are such that a radiochemically pure product
is obtained in injectable form and in activity (>10 mCi) suitable for the study of myocardial metabolism by emission-computerised
axial tomography. High pressure liquid chromatography and thin layer chromatography were used to assess the radiochemical
purity of each radiopharmaceutical. The specific activity of11C-labelled acetate was estimated by an enzymic procedure to be greater than 0.5 Ci/μmole. 相似文献
39.
Lemuel B. Wingard James F. Castner Shang J. Yao Sidney K. Wolfson Allan L. Drash Chung C. Liu 《Applied biochemistry and biotechnology》1984,9(1):95-104
Previous work has shown that glucose oxidase can be immobilized on platinum to give an electrode that responds potentiometrically to glucose over the clinically useful range of about 10-250 mg glucose/100 mL. The present studies were carried out with electrochemically pretreated platinum and with gold or porous graphite substituted for the platinum support. The presence of the enzyme gave a significantly enhanced potentiometric response over that obtained with the bare support for both the pretreated platinum and the porous graphite, but not with gold. However, with platinum the potentiometric response became more negative with increasing glucose concentration. With porous graphite, the potential changed in the positive direction as the glucose concentration was increased. Hysteresis was demonstrated for the platinum-enzyme electrode. Mass transfer measurements with a rotating ring-disc electrode (RRDE) showed measurable diffusional resistances to the transport of a model electroactive compound (potassium ferrocyanide) through a matrix of immobilized enzyme attached to the disc of the RRDE. These results are part of a larger study to define the source of the potentiometric response by examining the roles of the support and the mass transfer resistances through the immobilized enzyme matrix. 相似文献
40.
An ab initio molecular orbital calculation has been carried out for three different conformations of 1,3 propanediol, one of which permits intramolecular H-bond studied by ab initio quantum mechanical methods. The ΔE for H-bonding formation is compated to be 0.9 kcal/mole and the charge redistributions and molecular orbital energy changes are compared to those found in intermolecular H-bonds. 相似文献