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Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
2.
Kita Y Matsuda S Inoguchi R Ganesh JK Fujioka H 《The Journal of organic chemistry》2006,71(14):5191-5197
The Lewis acid-promoted rearrangement of 2,2,3,3-tetrasubstituted 2,3-epoxy alcohols with several kinds of protecting groups was investigated. When SnCl4 is used as a Lewis acid, the reaction proceeds in a regio- and stereo-controlled manner to afford two types of carbonyl compounds selectively from a single 2,3-epoxy alcohol only by changing the protecting group of the alcohol. The method was then applied to the formation of two types of acyclic and cyclic quaternary carbon centers from the single compound in optically active forms. 相似文献
3.
离子液体作为溶剂/催化剂用于卤代烃对胺的选择性烷基化反应 总被引:1,自引:0,他引:1
在三乙胺存在下,在离子液体([bmim]I和[bmim]PF6)中进行了各种卤代烃对胺类化合物中氨基的选择性烷基化反应.反应在相对温和的条件下进行,转化率和选择性优异.离子液体可以回收并重复使用. 相似文献
4.
Fourteen titanium alkoxides were synthesized for comparison of their catalytic properties in the bulk and solution polymerization of lactide (LA). In bulk polymerizations, they are effective catalysts in terms of polymer yield and molecular weight. Titanatranes gave polylactides with significantly increased molecular weight over more extended polymerization times, and those with five-membered rings afforded polymers in higher yields and with larger molecular weights than their six-membered ring counterparts. Steric hindrance of the rings was found to significantly affect polymer yields. Increased heterotactic-biased poly(rac-LA) was formed as the number of chlorine atoms increased in TiCl(x)(O-i-Pr)(4)(-)(x). In solution polymerizations, titanium alkoxides catalyzed controlled polymerizations of LA, and end group analysis demonstrated that an alkoxide substituent on the titanium atom acted as the initiator. That polymerization is controlled under our conditions was shown by the linearity of molecular weight versus conversion. A tendency toward formation of heterotactic-biased poly(rac-LA) was observed in the solution polymerizations. The rate of ring-opening polymerization (ROP) and the molecular weight of the polymers are greatly influenced by the substituents on the catalyst, as well as by factors such as the polymerization temperature, polymerization time, and concentration of monomer and catalyst. 相似文献
5.
The structure of 1,3-dehydro-5-adamantyl cation and its isoelectronic boron analogue 1,3-dehydro-5-boraadamantane as well as some related adamantane systems, hitherto unknown as persistent long-lived species, were investigated by using the density functional theory (DFT) method. (13)C and (11)B NMR chemical shifts of the compounds were also calculated using the IGLO method. Stabilization of the systems due to homoconjugation is discussed. 相似文献
6.
GK Johri Akhilesh Tiwari Saumya Saxena Rajesh Sharma Kuldeep Srivastava Manoj Johri 《Pramana》2002,58(3):563-567
Calculations for the relative width (Δω/ω0) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric
microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is
useful for the understanding of photonic crystals and occurrence of the photonic band gap. 相似文献
7.
Yasuyuki Kita Satoshi Matsuda Ryoko Inoguchi Jnaneshwara K. Ganesh Hiromichi Fujioka 《Tetrahedron letters》2005,46(1):89-91
The SnCl4-promoted rearrangement of 2,2,3,3-tetrasubstituted-2,3-epoxy-1-alcohol derivatives proceeded in a regio- and stereo-controlled manner to selectively give two types of rearranged products from a single isomer by changing the protecting group of the alcohol. 相似文献
8.
<正>The square soft-edge diaphragm with round angle is designed by Matlab,and is sent to a liquid crystal spatial light modulator by the computer.In order to obtain precompensation for the following laser system, local diaphragm transmission can be adjusted by feedback signals of surface-channel charge-coupled device (SCCD).This method can reduce the diffraction effect and realize no modulation,high stability,high homogeneity,and large scale laser beam.Several parameters of soft-edge diaphragms which affect the laser beam quality are studied systematically,and the optimized values are obtained.The method can avoid the serious modulation of hard edges and provide soft-edge diaphragms of different shapes in a fast and convenient way for the large scale laser beam system. 相似文献
9.
Microwave assisted preparation of a number of isatin derivatives is reported. A simple synthesis of (±)-convolutamydine-A, a potent compound against leukemia cells, is presented. 相似文献
10.
Kita Y Futamura J Ohba Y Sawama Y Ganesh JK Fujioka H 《The Journal of organic chemistry》2003,68(15):5917-5924
The Lewis acid treatment of 2,3-epoxysulfonates with 2,3-dialkyl substituents or 2-alkyl-3-aryl substituents produced the rearrangement products via C3-cleavage of the oxirane ring in high yields. On the other hand, 2-aryl-3-alkyl-2,3-epoxysulfonates produced the products via C2-cleavage of the oxirane ring. The sulfonyloxy groups of the alpha-sulfonyloxy ketones, having a chiral benzylic quaternary carbon center obtained by the rearrangement of 2-alkyl-3-aryl-2,3-epoxysulfonates, were reductively eliminated to give the ketones with a chiral benzylic quaternary carbon center. The method was applied to the formal synthesis of (-)-aphanorphine and total syntheses of (-)-alpha-herbertenol and (-)-herbertenediol. 相似文献
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