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991.
992.
Sonoluminescence spectra from argon-saturated NaCl solution were measured in the concentration range of 0.5-4 M at the frequency of 138 kHz. The line broadening of sodium atom emission was observed at various acoustic powers in the range from 1.8 to 16.2 W. The sodium D line showed a maximum intensity at a NaCl concentration of 2 M, which corresponded to the maximum production of OH radicals estimated by KI dosimetry. The effects of the addition of a small amount of ethanol on the line width and intensity were closely investigated at various acoustic powers. The sodium line width increases with ethanol concentration and also with power, whereas the line intensity is strongly quenched with increasing ethanol concentration. The results conclusively show that the sodium emission occurs in the gas phase within bubbles. The line broadening is due to interactions with high-pressure argon, and the maximum relative density of gas at bubble collapse was estimated to be 59.5 from the comparison with spectroscopic data. Further line broadening and quenching upon the addition of ethanol arise from collisions with gaseous products obtained from the decomposition of ethanol. The mechanism of sodium excitation is inferred to be as follows. Sodium ions enter bubbles as droplets, and salts are formed because of the high temperature within bubbles. Sodium atoms are generated by the dissociation of salts and then undergo electronic excitation by OH and H radicals. 相似文献
993.
The first total syntheses of two tricyclic sesquiterpenes 1 and 2, isolated from Jatropha neopauciflora, were completed from dimethyl D-tartrate in a stereoselective manner. The crucial steps in these syntheses involved not only the Rh(I)-catalyzed Pauson-Khand-type reaction of the allenene derivative leading to the exclusive formation of the bicyclo[4.3.0]nonenone framework possessing an angular methyl group but also a highly stereoselective construction of the isopropylcyclopropane ring. 相似文献
994.
Kuroda A Ishihara T Takeshige H Asakura K 《The journal of physical chemistry. B》2008,112(4):1163-1169
Water-repellent and self-cleaning properties of lotus leaves are considered to be due to its double roughness structure, protrusion structure (approximately 20 microm) and hairy structure (0.2-1.0 microm). In this study, attempts to fabricate a spatially periodic double roughness structure by two far-from-equilibrium self-organization phenomena, a directional viscous fingering and a spinodal dewetting, were made. A mixture of an octylsilyl titanium dioxide particle having an average diameter of 35 nm suspended in volatile silicone, decamethyl cyclopentasiloxane, and octyl p-methoxycinnamate was spread on a glass plate by dragging an applicator across the top. Formation of a stripe pattern parallel to the direction of dragging, called directional viscous fingering, was sometimes observed. Influences of spreading conditions on the pattern formation were analyzed. In addition, attempts were made to apply the stripe pattern formation to the preparation of a water repellent surface. We have succeeded in preparing a highly water-repellent surface by immersing a glass plate, on which a spatially periodic stripe pattern having a characteristic wavelength of 200-700 microm was formed, in water, after the completion of evaporation of decamethyl cyclopentasiloxane. In this case, dewetting patterns having a characteristic wavelength at around 5 microm were formed at the bottom part of the stripe patterns. Neither the surface on which only the mesoscopic spatially periodic stripe pattern was formed nor the one on which only the microscopic dewetting pattern was formed showed high water-repellent properties, indicating that the coexistence of the two different scales of patterns increased the water-repellent properties of the hydrophobic surface. 相似文献
995.
Asymmetric 1,4-addition of arylboronic acids to (E)-methyl 2-cyano-3-arylpropenoates proceeded in the presence of a rhodium catalyst (3 mol %) coordinated with a chiral diene ligand, (R,R)-Ph-bod*, to give high yields of the corresponding methyl 3,3-diaryl-2-cyanopropanoates with high enantioselectivity (up to 99% ee). This catalytic asymmetric transformation was applied to the asymmetric synthesis of (R)-tolterodine. 相似文献
996.
An organocatalyst-mediated, asymmetric Mannich reaction in the presence of water without using organic solvents has been developed. A highly reactive siloxytetrazole hybrid catalyst has been developed for the reaction of dimethoxyacetaldehyde, while the sodium salt of siloxyproline is an effective catalyst of alpha-imino glyoxylate. Excellent enantioselectivity can be realized, and the usage of organic solvents can be reduced compared to the conventional reactions in organic solvents. 相似文献
997.
Aikawa S Fujita N Myojo H Hayashi T Tanino T 《Chemical & pharmaceutical bulletin》2008,56(10):1431-1435
A newly developed mini-scale high shear granulator was used for scale-up study of wet granulation process from 0.2 to 200 L scales. Under various operation conditions and granulation bowl sizes, powder mixture composed of anhydrous caffeine, D-mannitol, dibasic calcium phosphate, pregelatinized starch and corn starch was granulated by adding water. The granules were tabletted, and disintegration time and hardness of the tablets were evaluated to seek correlations of granulation conditions and tablet properties. As the granulation proceeded, disintegration time was prolonged and hardness decreased. When granulation processes were operated under the condition that agitator tip speed was the same, similar relationship between granulation time and tablet properties, such as disintegration time and hardness, between 0.2 L and 11 L scales were observed. Likewise, between 11 L and 200 L scales similar relationship was observed when operated under the condition that the force to the granulation mass was the same. From the above results, the mini-scale high shear granulator should be useful tool to predict operation conditions of large-scale granulation from its mini-scale operation conditions, where similar tablet properties should be obtained. 相似文献
998.
Takeshi Inoue Takeshi Furukawa Akihiro Yoshimi Tsubasa Nanao Masatoshi Chikamori Kunifumi Suzuki Hironori Hayashi Hirokazu Miyatake Yuichi Ichikawa Masato Tsuchiya Naoto Hatakeyama Sota Kagami Makoto Uchida Hideki Ueno Yukari Matsuo Takeshi Fukuyama Koichiro Asahi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2016,70(6):129
999.
Synthesis of Furoxans (1,2,5‐oxadiazole 2‐oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non‐Acidic Media and Mechanistic Study
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Ryosuke Matsubara Akihiro Ando Yuta Saeki Kazuo Eda Naoki Asada Tomoaki Tsutsumi Yong Soon Shin Masahiko Hayashi 《Journal of heterocyclic chemistry》2016,53(4):1094-1105
Diverse furoxans (1,2,5‐oxadiazole 2‐oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid‐sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism. 相似文献
1000.
Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β‐Keto Esters
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Dr. Kazushi Agura Dr. Yukiko Hayashi Mari Wada Daiki Nakatake Prof. Dr. Kazushi Mashima Prof. Dr. Takashi Ohshima 《化学:亚洲杂志》2016,11(10):1548-1554
The electronic effects of tetranuclear zinc cluster catalysts on transesterification were investigated by changing the carboxylate ligands in the clusters. High catalyst activity crucially depended on the balance between Lewis acidity and Brønsted basicity of the catalyst; this was consistent with the dual activation of both the electrophile and nucleophile by the cooperative zinc centers. In addition, tetranuclear zinc cluster catalysts achieved the transesterification of β‐keto esters with unprecedented levels of broad substrate generality, in which a newly developed pentafluoropropionate‐bridged zinc cluster and 4‐dimethylaminopyridine additive greatly improved the reactivity of sterically congested α‐ and α,α‐disubstituted β‐keto esters. 相似文献