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81.
Masayuki Yamane 《Journal of Sol-Gel Science and Technology》1997,8(1-3):483-487
A thick silica gel film, corresponding to the glass film of 10–20 micron in thickness, has been formed at the interface between
two immiscible liquids, hexane and water, using E-40, a partially polymerized silicon alkoxide, as the precursor. The film
formation was possible using both acid- and base-catalyzed water, but was greatly dependent on the type of catalyst. Only
the trace of a film was observed for the system catalyzed with a strong electrolyte such as HCl, HNO3 or NaOH, while a gel film, corresponding to the glass film of several to 10 micron in thickness was formed with a weak electrolyte
such as ammonia, organic acid like acetic acid, citric acid, etc., of similar pH value. The direct introduction of organic
base catalyst like triethylamine in hexane was much more effective than the use of ammonia water, suggesting that the polymerization
of E-40 to form a gel film takes place in the organic phase, where water molecules, as well as undissociated ammonia or organic
acids, can diffuse in. 相似文献
82.
以ZnO纳米柱阵列为模板, 采用溶胶-凝胶法制备出TiO2/ZnO和N掺杂TiO2/ZnO的复合纳米管阵列. 扫描电镜(SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis)的结果表明: 两种阵列的纳米管均为六角形结构, 直径约为100 nm, 壁厚约为20 nm; 在N-TiO2/ZnO复合纳米管阵列中, 掺入的N离子主要是以N-Ox、N-C和N-N的形式化学吸附在纳米管表面, 仅有少量的N离子以取代式掺杂的方式占据TiO2晶格O的位置; 表面N物种形成的表面态能级和取代式掺杂导致带隙的窄化, 增强了纳米管阵列的光吸收效率, 促进了光生载流子的分离. 光催化实验结果表明, N离子的掺杂有利于N-TiO2/ZnO复合纳米管阵列光催化活性的提高. 相似文献
83.
E. V. Gorobetz A. N. Kasatkin A. V. Kutchin G. A. Tolstikov 《Russian Chemical Bulletin》1994,43(3):466-470
Hydroalumination of methyl nopol ether with a LiAlH4-3AlBr3 system is accompanied by a skeleton rearrangement and gives 6-dibromoalumo-7-methoxymethyl-2-menthene. Further hydroalumination affords a mixture of 2,6- and 2,5-bis(dibromoalumo)-7-(methoxymethyl)menthanes in 8020 ratio. Hydrolysis and oxidation of these organoaluminum compounds were carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 506–510, March, 1994. 相似文献
84.
V. R. Kartashov T. N. Sokolova I. V. Timofeev E. V. Skorobogatova N. S. Zefirov 《Russian Chemical Bulletin》1994,43(5):760-768
The kinetics of mercuration of bornylene and cyclohexene in different solvents in the presence of NaOAc and LiClO4 has been investigated. Addition of NaOAc sharply decreases the rate of addition reactions of mercuric acetate to bornylene and cyclohexene in alcohols; the main direction of the mercuration of bornylene is the formation of acetoxy-adducts, and the yield of solvo-adducts decreases from 76 % in the absence of NaOAc, to 19 % in the presence of the salt (4·10–3 mol L–1). A reaction scheme involving the participation of intermediate ion pairs and a solvated mercurinium ion is suggested and confirmed by a steady-state concentration method. The influence of NaOAc on the rate of the reaction and on product formation is realized through the common ion effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 819–826, May, 1994. 相似文献
85.
Biflavonoids, widely distributed in natural plants, had strong biological activities including spasmolysis, peripheral vasodilatation, antibradykinin activity and antispasmogenic action against prostaglandin PGE1, inhibition of cyclic GMP and cyclic AMP phosphodiesterase and inhibition of hepatoma cells. Recently, some biflavonoids were demonstrated to enhance suppersion of lymphocyte proliferation, inhibition of phospholipaseCr1, anti-inflammatory activity, anti-HIV activity, anticompleme… 相似文献
86.
A radical mechanism of the reaction of molybdenum carbonyl complexes with bis(triethylgermyl)mercury
M. I. Sykhrannova A. N. Tatarnikov S. Ya. Khorshev E. N. Gladyshev 《Russian Chemical Bulletin》1993,42(9):1585-1587
The reaction of [Cp(CO)3Mo]2 with (Et3Ge)2Hg occurs in toluene and THF by a radical mechanism. The interaction between [Cp(CO)3Mo]2Hg and (Et3Ge)2Hg has a radical character only in THF. The formation of Cp(CO)3MoH at the first stage of these reactions substantially affects the further course of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1648–1650, September, 1993. 相似文献
87.
N. A. Mohamed Farook 《Journal of solution chemistry》2007,36(3):345-356
The oxidation kinetics of substituted and unsubstituted 4-oxoacids (S) by N-chlorosaccharin (NCSA) have been studied in aqueous acetic acid media. The reaction follows first-order kinetics in each
of the 4-oxoacids, NCSA and H+. The effect of changes in the electronic nature of the substrate reveals that positive charge develops in the transition
state. Based on the kinetic results and product analysis, a suitable mechanism has been proposed for the reaction of NCSA
with 4-oxoacids. 相似文献
88.
用套索冠醚N,N′-双(2-甲基吡啶)-二氮杂-18-冠-6作为固定相,涂渍在弹性石英毛细管内,测其柱效、惰性、热稳定性、平均极性及选择性等性质.其结构由元素分析、红外光谱、核磁共振及质谱分析的试验数据所证实.试验表明,它具有良好的色谱性能、中等极性,适用于对醇、卤代烃、芳香烃等各类异构体的分离,并用分子结构观点探讨了保留机理. 相似文献
89.
William H. Donovan 《Structural chemistry》1995,6(4-5):243-254
Ab initio and semiempirical molecular orbital calculations have been applied to study the concerted and stepwise isotopic scrambling mechanisms of 2-chloroethyl methyl sulfide in the gas phase and in aqueous solution. The calculations reveal the structural details of the reactants, transition structures, and intermediates involved in this reaction and provide relative energy estimates. The concerted mechanism is found to be competitive with the stepwise mechanism in the gas phase, but the stepwise mechanism is favored in aqueous solution as no true transition structure for the concerted mechanism could be found using the solvation models. A combined approach of evaluating solvation energies with the generalized-Bom-plus-surface-tensions SM
x
solvation models of Cramer and Truhlar at ab initio optimized geometries is found to deliver the best agreement with experimentally determined reaction barriers. Together with the recent experimental results of McManus and co-workers, the present study provides insights into the controlling factors involved in the elementary reaction steps of sulfur mustards and a solid foundation for investigations into more complex reactions of related compounds. 相似文献
90.
ZHANG Shu-dong KONG Xiang-he ZHU Xiang-jun WANG Yan JIANG Su-rong 《高等学校化学研究》2006,22(5):621-625
IntroductionReactions of metal ions with neutral molecules orclusters produce a variety of metal complex ions andother new series of cluster ions including cations andanions.The laser ablation-molecular beam(LA-MB)method has marked its relevance in the st… 相似文献