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121.
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The DIBAL reduction of 2-phenylethyl 3,3,3-trifluoro-2-methylpropionate 2 at -78 degrees C afforded the aluminum acetal 3, and this intermediate, on worming up to 0 degrees C, was found to slowly decompose into the corresponding aldehyde 4, which smoothly reacted with appropriate nucleophiles in a one-pot manner in good to excellent yields with up to 93% diastereoselectivity. 相似文献
124.
T. Nagai K. Sakai T. Asaka A. Yamazaki Y. Matsui 《Journal of solid state chemistry》2006,179(6):1898-1903
The crystal structure of our newly discovered Sr-Co-O phase is investigated in detail through high-resolution electron microscopy (HREM) techniques. Electron diffraction (ED) measurement together with energy dispersive X-ray spectroscopy (EDS) analysis show that an ampoule-synthesized sample contains an unknown Sr-Co-O ternary phase with monoclinic symmetry and the cation ratio of Sr/Co=1. From HREM images a layered structure with a regular stacking of a CdI2-type CoO2 sheet and a rock-salt-type Sr2O2 double-layered block is observed, which confirms that the phase is the parent of the more complex “misfit-layered (ML)” cobalt oxides of [MmA2Om+2]qCoO2 with the formula of [Sr2O2]qCoO2, i.e. m=0. It is revealed that the misfit parameter q is 0.5, i.e. the two sublattices of the CoO2 sheet and the Sr2O2 block coexist to form a commensurate composite structure. We propose a structural model with monoclinic P21/m symmetry, which is supported by simulations of ED patterns and HREM images based on dynamical diffraction theory. 相似文献
125.
Low water/methanol permeable Nafion/CHP organic-inorganic composite membrane with high crystallinity
High methanol crossover is one of the main issues of the polyelectrolyte in direct methanol fuel cells (DMFCs). In order to decrease methanol crossover, we introduced a new method that crystallinity control was performed with incorporating CHP (calcium hydroxyphosphate) into Nafion solution. As a result, crystallinity in the composite membranes increased with CHP content compared to cast Nafion accompanying the formation of new crystalline peaks in the original amorphous region of Nafion. On the other hand, water uptake content, methanol sorption/desorption permeability and methanol crossover in the composite membranes remarkably decreased. We conclude that an increase in crystallinity due to the strong interfacial adhesion between Nafion and CHP can suppress the methanol crossover. 相似文献
126.
Yamazaki D Nishinaga T Tanino N Komatsu K 《Journal of the American Chemical Society》2006,128(45):14470-14471
A terthiophene fused with bicyclo[2.2.2]octene units only at both ends was newly synthesized. Since there is no steric hindrance at the central position, this terthiophene has a possibility to interact only at the central position. One-electron oxidation of this terthiophene afforded a highly stable radical-cation salt as deep blue crystals. The result of X-ray crystal structural analysis demonstrated a characteristically bent pi-dimereric structure, which is formed by mutual attraction of single radical-cation species at the central position to minimize the steric repulsion. Remarkably short intermolecular distances between the central thiophene rings of each unit of the dimeric pair, that is, 2.976(10) A for Cbeta-Cbeta, 3.091(10) A for Calpha-Calpha, and 3.779(3) A for S-S, are good indication of the existence of attracting interaction, which was confirmed by theoretical calculations. This interaction was experimentally demonstrated by the reversible formation of the pi-dimer in CH2Cl2 solution using ESR and UV-vis-NIR spectroscopy. The crystal of the pi-dimer is in its singlet state and ESR silent in the solid state at 300 K, but the signal of a triplet state of the pi-dimer was observed by heating the solid at 400 K. This indicates that this pi-dimer has a quite small triplet-singlet enegy gap and the triplet state is thermally accessible. 相似文献
127.
The adsorption of ten gases on the flexible metal organic framework material [Cu(dhbc)(2)(4,4'-bpy)]·H(2)O (Cu(db)) has been measured over a wide range of temperatures and pressures. The gate opening condition and driving force behind gate adsorption for Cu(db) were discussed by examining the adsorption isotherms. The adsorption isotherms for each adsorbate can be generalized to a characteristic curve using the adsorption potential energy (ε) and the adsorption volume. The adsorption potential (ε(gate)) at gate opening is almost constant over a wide range of temperatures; thus, the gate pressure at a desired temperature can be deduced using the ε(gate) evaluated from one adsorption isotherm. The gate opening capacity of the gases was arranged in the order: CO(2)≒N(2)O>C(2)H(4)≒Xe>CH(4)>CO>O(2)>Ar≒N(2)>H(2), which is governed by the interaction energy between the outer surface of Cu(db) and the adsorbate. It is suggested that the gate effect is brought about when the integral interaction energy of adsorbates with the Cu(db) surface exceeds a defined limit correlating with the π-π stacking energy of Cu(db) layers. 相似文献
128.
A. Yamazaki Y. Inoue M. Koike T. Sakamoto R. Otsuka 《Journal of Thermal Analysis and Calorimetry》1993,40(1):85-97
Thomsonite with ideal chemical composition and with an ordered framework structure was synthesised hydrothermally from zeolite Na?A, which was ground to X-ray amorphous, with 0.05 mol dm?3 CaCl2 solution at 200°C. The dehydration behaviour of the prepared thomsonite was examined by TG-DTA. It was revealed that thomsonite lost most of zeolitic water below 450°C in three steps at about 180°, 340° and 390°C. The peak profiles of, the two higher-temperature endotherms were sharp and similar, and the weight loss at each step was approximately equal. 相似文献
129.
130.
Masahiro Kihara Shin‐Ichiro Kohama Shota Umezono Kanji Wakabayashi Shinichi Yamazaki Kunio Kimura 《Journal of polymer science. Part A, Polymer chemistry》2011,49(5):1088-1096
Poly(p‐oxybenzoyl) (POB) crystals were prepared by reaction‐induced crystallization during direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides. Polymerizations were carried out at 300 °C in dibenzyltoluene at a concentration of 1% with three kinds of anhydrides of boronic acid such as 3,4,5‐trifluorophenylboronic acid (TFB), 4‐methoxyphenylboronic acid (MPB) and 4‐biphenylboronic acid (BPB). The POB crystals were formed as precipitates in the solution and the morphology was considerably influenced by both the structure of the boronic anhydride and its concentration (cB). Needle‐like crystals were firmed in the presence of TFB anhydride (TFBA) at cBs of 5 and 10 mol % by the spiral growth of lamellae. Spherical aggregates of slab‐like crystals were formed at cBs from 50 to 100 mol %. The polymerization with MPB anhydride and BPB anhydride (BPBA) also yielded the needle‐like crystals at cBs of 50 and 5 mol %, respectively. The polymerization with TFBA at lower cB was favorable to prepare the needle‐like crystal. Molecular weight was also influenced by the structure of the boronic anhydride and cB. Mn increased generally with cB and BPBA gave the highest Mn of 14.7 × 103 at cB of 100 mol %. The loose packing of the molecules in the crystal caused by the bulkiness of the end‐groups made the polymerization in the crystals more efficiently. Morphology and molecular weight of the POB crystals could be controlled by the chemical structure and the content of boronic anhydride. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献