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71.
72.
The OH proton chemical shifts of methanol referred to the CH3 proton in the methanol — benzene-d6 system have been measured from room temperature up to the supercritical region. MD simulations have also been performed at the same composition as experiment at 575 K. The chemical shift results in the supercritical region are in good agreement with those of pure methanol at the same density within experimental errors. The results of NMR and MD simulation suggest that the hydrogen-bonded structure of methanol is practically not affected by addition of benzene molecules. 相似文献
73.
74.
Suzuki N Kiba S Kamachi Y Miyamoto N Yamauchi Y 《Physical chemistry chemical physics : PCCP》2012,14(10):3400-3407
We fabricate mesoporous silica/silicone composites in a simple way and systematically examine their thermal stability, swelling characteristic, mechanical strength, and transparency. Simple calculations show that more than 90 vol% of mesopores are filled with silicone rubbers. Compared to non-porous silica/silicone composites, mesoporous silica/silicone composites showed a lower coefficient of linear thermal expansion (CTE). In addition, dramatic improvements of the tensile strength and Young's modulus are obtained with mesoporous silica/silicone composites. Furthermore, mesoporous silica/silicone composites show higher transparency than non-porous silica/silicone composites. 相似文献
75.
Haruaki Kurasaki Iwao Okamoto Dr. Nobuyoshi Morita Dr. Osamu Tamura Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(46):12754-12763
This article describes in detail the first total synthesis of grandisine alkaloids, grandisines B, D, and F, which show affinity for the human δ‐opioid receptor. The key steps in this synthesis are construction of the isoquinuclidinone moiety of 2 by intramolecular imine formation and the tetracyclic ring system of 4 by stereoselective ring closure of the enolate of amine 8 generated by 1,4‐addition of ammonia to 9 . Synthesis of key intermediate 9 featured a highly stereoselective Brønsted acid mediated Morita–Baylis–Hillman (MBH) reaction via the N‐acyl iminium ion. 相似文献
76.
Liu R von Malotki C Arnold L Koshino N Higashimura H Baumgarten M Müllen K 《Journal of the American Chemical Society》2011,133(27):10372-10375
A new class of macrocyclic metal-N(4) complexes [MN(4)](n) (M = Co and Fe) were designed and synthesized based on a triangular ligand. Their unique triangular trinuclear structure provides a high density of active sites and facilitates the reduction of dioxygen via a four-electron pathway. Among them, a [CoN(4)](3)/C catalyst (20 wt %) exhibits high catalytic activity and long-time stability for the oxygen reduction reaction (ORR) in alkaline conditions, superior to the commercial Pt/C catalyst. Such structurally well-defined [MN(4)](n) complexes provide a platform for a new generation of nonprecious metal catalysts (NPMCs) for fuel cell applications. 相似文献
77.
As a possible candidate for the left-handed metamaterial with negative permeability, a series of Ti, Co-substituted M-type barium hexaferrite BaFe12−x(Ti0.5Co0.5)xO19 (x=0, 1, 2, 3, 4 and 5) was prepared by citrate precursor method. The formation processes of the substituted barium hexaferrite compounds from the precursors were followed by the measurements of powder X-ray diffraction (XRD), Infrared absorption spectra (FT-IR), and thermogravimetry and differential thermal analysis (TG/DTA) coupled with mass spectroscopy (MS). In the case of the non-substituted sample, the formation of the barium hexaferrite is regulated by the thermal decomposition of BaCO3 and the solid-state reactions of BaO and Fe2O3 in the temperature range from 800 to 1100 K. The formation temperature of the substituted BaFe12−x(Ti0.5Co0.5)xO19 is higher than that for the non-substituted sample and increases with the value of x, due to the effects of carbonate ions incorporated by the partial substitution of Fe3+ by (Ti0.5Co0.5)3+. On heating up to ca. 1200 K, all the substituted samples transform into the magenetoplumbite phase as is the non-substituted sample. The compositional dependence of the magnetic properties of the substituted barium hexaferrite was investigated by the magnetization measurement. The decrease in the magnetic anisotropy was confirmed by the change in the magnetization curve and coercivity HC with the composition x. A negative permeability spectrum was observed in the BaFe9(Ti0.5Co0.5)3O19 in the frequency range from 2 to 4 GHz. 相似文献
78.
For the precipitation of calcium carbonate polymorphs in ethanol/water solutions of calcium chloride by the diffusion of the gases produced by sublimation–decomposition of solid ammonium carbonate, polymorph selection and morphology control of the precipitates were demonstrated by the effect of ethanol/water ratio in the mother liquor. The precipitated phases change systematically from gel-like aggregates of hydrated amorphous calcium carbonate in the absolute ethanol solution to well-shaped rhombohedral particles of calcite in the absolute aqueous solution via almost pure phase of vaterite with dendrite structure in 75%-ethanol/25%-aqueous and 50%-ethanol/50%-aqueous solutions. On heating the precipitated sample in flowing dry nitrogen, all the samples transformed to calcite before the thermal decomposition, where the thermal decomposition temperature shifts to higher temperatures with increasing the water content in the mother liquor due to the systematic increase in the particle size of calcite. Accordingly, the present method of controlled precipitation of calcium carbonate polymorphs is also useful to control the particle size and reactivity of calcite produced by heating the precipitates. Selecting vaterite with dendrite structure from the present series of precipitated samples, the structural phase transition to calcite was characterized as the three-dimensional growth of rhombohedral particles of calcite with the enthalpy change ΔH = ? 2.8 ± 0.1 kJ mol?1 and the apparent activation energy Ea = 289.9 ± 5.8 kJ mol?1. 相似文献
79.
80.
Toshio Koizumi Nobuyoshi Saeki Hisatoshi Abematsu Shu-Ichi Terada Osamu Moriya Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1999,37(16):3419-3426
Synthesis and radical polymerization behavior of N-vinylsaccharin (1) are described. Radical homopolymerization of 1 was carried out in the presence of a radical initiator for 24 h to afford the polymer containing a saccharin moiety in the side group, which was insoluble in common organic solvents. Among the copolymers of 1 with various vinyl monomers such as vinyl acetate (VAc), methyl acrylate (MA), acrylonitrile (AN), and styrene (St), only the copolymer [copoly(1-St)] obtained from 1 and St was soluble in common organic solvents. In the copolymerization of 1 and St, the Q and e values of 1 were estimated to be 0.10 and −1.60, respectively. These values are similar to those of N-vinylphthalimide (Q = 0.36, e = −1.52). The reaction of copoly(1-St) with LiAlH4 was carried out in THF for 24 h to convert the saccharin moiety into the ring-opened structure bearing hydroxy and sulfonamide groups. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3419–3426, 1999 相似文献