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排序方式: 共有139条查询结果,搜索用时 15 毫秒
1.
Praveen K. Tandon Gayatri Sumita Sahgal Manish Srivastava Santosh B. Singh 《应用有机金属化学》2007,21(3):135-138
Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H2O2. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
Fukuji Higashi Chong Su Cho Hideo Kakinoki Osao Sumita 《Journal of polymer science. Part A, Polymer chemistry》1977,15(10):2303-2309
Semiconducting organic polymer was obtained by the modification of polyacrylamide (PAAm)–Cu++ chelate with iodine in acetone. Favorable conditions for preparing the chelate effective for the conduction were investigated. Surface resistivities were affected by the amounts of cupric salts and iodine, satisfactory results being given by about 25 wt % of the salts based on PAAm and more than 1 wt % of iodine on the chelate. The conductivity was also varied with the degree of neutralization of the chelate in solution, and optimal values were obtained by addition of about an equimolar amount of potassium hydroxide to cupric salts. Effective structures of the polymer chelate in solution were assumed on the basis of the visible and the NMR spectra and potentiometric titration. 相似文献
3.
The reactions of beta- and alpha-pyranose peracetates with PCl5 gave products regioselectively chlorinated. The reactions of 1,2,3,4,6-penta-O-acetyl-beta-D-glucopyranose (5) and -beta-D-galactopyranose (6) with PCl5 in CCl4 and that of methyl 2,3,4-tri-O-acetyl-beta-D-glucuronatopyranose (7) with PCl5 in toluene gave 2-O-trichloroacetyl-beta-D-pyranosyl chlorides 4, 12 and 14, respectively, as major products, and alpha-D-pyranosyl chlorides 11, 13 and 15, respectively, as minor products. On the other hand, the reactions of compounds 8 and 9 which were alpha-anomers of 5 and 6, respectively, with PCl5 gave as major products transformed acetyl groups at C-6 to -C(Cl) = CCl2 or -C(Cl)2-CCl3 group (16 and 17 from 8 and 18 from 9). The same reaction of 10, which was alpha-anomer of 7, gave alpha-chloride 15 as a major product. The glycosidation of sugar derivative 4 with sarsasapogenin 23 gave beta-glycoside 24 (29.1%) and alpha-glycoside 25 (46.9%), and that of 12 with 23 gave beta-glycoside 26 (24.0%) and alpha-glycoside 27 (40.8%). The improvement of the yields of beta-glycosides 24 and 26 (66.9 and 62.1% for 24 and 26, respectively) in the glycosidations were accomplished by the employment of alpha-bromides 28 and 29 obtained from 4 and 6, respectively. The glycosidations of monoglycosides 30 and 31 obtained by the treatment 24 and 26, respectively, with ammonia-saturated ether with sugar acetate bromides 32 and 34 gave diglycoside derivatives 35 and 33, respectively. 相似文献
4.
Abstract: The addition of (N-alkyl-N-alkoxyammine)dimethylaluminum chlorides to nitriles provides a convenient route to little investigated N-alkoxy amidine hydrochlorides. A survey of the scope of this reaction is presented. 相似文献
5.
Sumita Rani Mukesh Kumar Sumit Sharma Dinesh Kumar 《Journal of Sol-Gel Science and Technology》2014,71(3):470-476
Fine powders of zirconium oxide (ZrO2) were prepared using zirconium oxychloride by combustion method. The crystalline size of pure ZrO2 was in range of 14–45 nm. Graphene was incorporated in ZrO2 using graphene oxide as precursor and reducing it with hydrazine hydrate. X-Ray diffraction, Fourier transform infra-red spectroscopy, thermogravimetric analysis and Raman spectroscopy methods were used to characterize the samples. The role of graphene in structural transformation of ZrO2 to monoclinic phase was clearly observed. 相似文献
6.
Masao Sumita Hibeki Abe Hiroyuki Kayaki Keizo Miyasaka 《Journal of Macromolecular Science: Physics》2013,52(1-2):171-184
The electrical conductivities of carbon-black-filled low-density polyethylene (LDPE), poly(methyl methacrylate) (PMMA), and poly(vinyl chloride)-vinyl acetate (PVC/ VAc) copolymer were measured as functions of carbon content and melt viscosity of the matrix at the temperatures at which the composites were prepared. Sharp breaks in the relationship between the carbon filler content and the conductivity of composites were observed in all specimens at some content of the carbon filler. The conductivity jumps as much as 10 orders of magnitude at the break point. This phenomenon has been known as the “percolation threshold”. The critical carbon content corresponding to the break point 相似文献
7.
8.
In CRM (Customer Relationship Management), the importance of a segmentation method for identifying good customers has been increasing. For evaluation of different segmentation methods, Accuracy often plays a key role. This indicator, however, cannot distinguish two types of errors. The purpose of this paper is to overcome this pitfall by introducing two different indicators: Recall and Precision. Assuming that a promotion is addressed exclusively to the selected target customers, the financial effectiveness of the underlying segmentation method is expressed as a function of Recall and Precision. An optimization problem is then formulated so as to maximize the financial measure by finding the optimal threshold level in terms of the severeness for estimating the target set. By introducing a functional form which represents correctness and mistakes about the target set, the unique optimal solution is derived explicitly. The proposed approach is validated by using real customer purchase data. 相似文献
9.
Liang Bao Liu Noriko Murakami Masao Sumita Keizo Miyasaka 《Journal of Polymer Science.Polymer Physics》1989,27(12):2441-2450
The effect of molecular weight distribution (MWD) on the ultradrawability and mechanical properties of solution-cast films of ultrahigh-molecular-weight polyethylene (UHMW-PE) has been investigated using tensile and dynamic mechanical measurements. The MWD has a marked effect on ultradrawability and thus on the ultimate mechanical properties such as the tensile modulus. It is proposed that UHMW-PE with a narrow MWD(N-PE) attains the ultimate structure at a lower draw ratio than UHMW-PE with a broad MWD(B-PE) because of the existence in the latter of less fully extended intercrystalline tie chains. It is found that, at the same drawing temperature (100°C), N-PE shows a higher modulus than B-PE at draw ratios up to 150 x, which is assumed to be the ultimate value for N-PE. 相似文献