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101.
Villa de P AL Alarcón E Montes de Correa C 《Chemical communications (Cambridge, England)》2002,(22):2654-2655
MCM-41 was found to be an active heterogeneous catalyst for the synthesis of nopol by the Prins condensation of beta-pinene and paraformaldehyde, but Sn-MCM-41 in which Sn has been grafted on MCM-41 by chemical vapor deposition is far more active and combines high efficiency and recyclability. 相似文献
102.
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105.
Kaliyamoorthy Panneerselvam Kizakkekoikkal K. Chacko Edwin Weber Hans-Jürgen Kühler 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(4):337-347
Single crystal X-ray analysis of a 1 : 2 complex between the dinaphthopyridino-l8-crown-6 host (1) and acetonitrile is reported. Crystals of the complex are monoclinic,P21/c witha = 12.178(5),b = 8.186(1),c = 30.873(1) Å, = 96.86(1)°, andD
c = 1.25 g cm–3 forZ = 4. The host molecule reveals an approximate mirror symmetry and exists in a so-called dentist's chair conformation. One of the acetonitrile guest molecules is involved in possible weak interactions to two oxygen atoms of the host macroring, while the other fills free lattice space only. 相似文献
106.
Bruno Albrecht Michael Allan Edwin Haselbach Louis Neuhaus Pierre-Alain Carrupt 《Helvetica chimica acta》1984,67(1):220-223
Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured. I = 8.20 eV and I = 8.65 eV were found, the dominant vibrational progression (? = 725 cm?1) indicating that in the course of 1(X)→1 +( X? ) flattening around the N-atom occurs. The Franck-Condon profile of this band, however, suggests that a skeletal mode of ? ≈ 1400 cm?1 (observed also in the iso-π-electronic systems vinyl-alcohol-cation and allyl radical) may also be excited. Comparison with the data for the isomer acetaldehyde-imine 2 and its cation s + shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from the neutrals to the cations. 相似文献
107.
Rate constants of the cleavage reaction of silicon aryl linkages with HBr were estimated for various aryl derivatives by means of NMR. A row of substituents was obtained, dependent on the cleavage rates. Correlation with theHammett function shows the electrophilic character of the reaction. The different cleavage rates give the possibility for specific cleavages of aryl groups from silanes. 相似文献
108.
The minimum-uncertainty states for systems with many degrees of freedom are investigated. The limiting situation, relevant to the electromagnetic field, is discussed and it is pointed out that the states that minimize Δp Δq do not tend to the coherent states. These latter, including the vacuum state, are minimum-uncertainty states for the transverse electric and magnetic fields. In an appendix a direct method to obtain the wave functional for the vacuum is presented. 相似文献
109.
Temperature dependence of the 1H chemical shift of tetramethylsilane in chloroform, methanol, and dimethylsulfoxide 总被引:1,自引:0,他引:1
The chemical shift of tetramethylsilane (TMS) is usually taken to be zero. However, it does vary slightly with temperature, having obvious implications for studies of temperature effects on chemical shifts. In this work, we measure the variation in the chemical shift of TMS with temperature in three solvents, CDCl3, CD3OD, and DMSO-d6, relative to the resonant frequency of 3He gas, which can be reasonably assumed to be temperature independent. In all three solvents, the average temperature coefficient over a wide temperature range is about -6 x 10(-4) ppm/degrees C, a factor of five smaller than that previously reported in the literature. Data are included for 3He resonance frequencies over a temperature range of -110 to +180 degrees C, along with new measurements of volume magnetic susceptibilities of the three solvents and estimates of their temperature dependence. A novel method is used to provide temperature measurement via 2H resonances of methanol and ethylene glycol samples, which can concurrently be used for field/frequency locking. 相似文献
110.
Chow HS Constable EC Housecroft CE Kulicke KJ Tao Y 《Dalton transactions (Cambridge, England : 2003)》2005,(2):236-237
Electron exchange between [Co(terpy)2]3+ and [Co(terpy)2]2+ can be monitored by 1H NMR exchange spectroscopy and allows the cobalt(II) spectra to be fully assigned. 相似文献