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41.
42.
研究了一系列二芳甲酰甲烷化合物在不同溶剂中的分子内氢键及酮-烯醇互变异构平衡。δ_(OH)和lgK与取代基常数(σ)之间均有良好的线性关系存在。+I和+R取代基使分子内氢键增强,而使烯醇式含量降低。 相似文献
43.
Densities have been measured for the electrolyte (NaCl, NaBr and NaI)‐monosaccharide (D ‐mannose and D‐ribose)‐water solutions at 298.15 K. These data have been used to calculate the apparent molar volumes of the saccharides (VΦ,S) and electrolytes (VΦ,E) in the studied solutions. Infinite dilution apparent molar volumes, VΦ,S0 and VΦ,E0, have been evaluated, together with the standard transfer volumes of the saccharides (ΔtVS0) from water to aqueous electrolyte solutions and those of the electrolytes (ΔtVE0) from water to aqueous saccharide solutions. It was shown that both the ΔtVS0 and ΔtVE0 values are positive and increase with increasing molalities of sodium halides and saccharides, respectively. Overall, the ΔtVS0 and ΔtVE0 values have the order of NaCl > NaBr > NaI except for NaI‐ribose and NaI‐ribose. Volumetric interaction parameters for the electrolyte‐monosaccharide pairs in water were obtained and interpreted by the stereochemistry of the monosaccharide molecules and the structural interaction model. 相似文献
44.
微波辅助萃取/气相色谱-质谱联用分析蔬菜中的有机磷农药 总被引:29,自引:0,他引:29
建立了微波辅助萃取(MAE)/气相色谱-质谱联用法(GC-MS)测定蔬菜样品中二嗪磷、水胺硫磷的分析方法,研究了不同溶剂的萃取效率。选择二氯甲烷为萃取溶剂,采用二因素三水平的正交设计实验优化了萃取溶剂体积和萃取时间。方法的线性范围分别为二嗪磷和对硫磷4ng/g-400ng/g,水胺硫磷20ng/g-400ng/g,检出限分别为二嗪磷和对硫磷4ng/g-400ng/g、水胺硫磷20ng/g-400ng/g,检出限分别为二嗪磷0.29ng/g、对硫磷1.70ng/g、水胺硫磷2.30ng/g。测定200.0ng/g和50.0ng/g加标蔬菜样品,回收率为72.2%-102.0%,RSD为1.5%-11.0%。与传统的机械振荡萃取法相比,不仅萃取效率相当,而且还具有省时省溶剂的优点。 相似文献
45.
46.
带咪唑、苯并咪唑等配位基团的过渡金属配合物是一类很重要的物质[1~ 9] 。本文探讨它与Zn(Ⅱ )的配位性质及配合物的晶体结构。1 实验部分1 .1 标题配合物的合成及表征将 92mg 2 (0 氯苯基 )苯并咪唑和 40mgZnCl2(AR)分别溶于无水乙醇(AR)后混合均匀 ,于室温下静置 3 0天 ,析出长方体形无色晶状物 ,产率为 47%。采用Perkin Elmer 2 4 0C元素分析仪测定配合物中C、H、N含量。用DDS 1 1C数显电导率仪 ,以DMF为溶剂测定配合物的摩尔电导。采用Nicolet5DX B傅立叶变换红外光谱仪 ,KBr压… 相似文献
47.
Li Z Chen Z Cui H Hales K Qi K Wooley KL Pochan DJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7533-7539
Disk and cylindrical micellar assemblies were formed through self-organization of poly(acrylic acid)-b-poly(methyl acrylate)-b-polystyrene (PAA-b-PMA-b-PS) amphiphilic triblock copolymers with organic diamines as counterions in water/ tetrahydrofuran (THF) solvent mixtures. The system was investigated by means of transmission electron microscopy and cryogenic transmission electron microscopy. It was found that the assembled-state morphologies could be modified by alteration of the type and concentration of cationic diamine counterion undergoing interaction with the negatively charged, polyelectrolyte PAA corona block, the relative amount of water in the water/THF mixture, and the hydrophobic block chain length. Multivalency of the organic amine counterion was critical for disk formation. It was further demonstrated that a single block copolymer underwent disc-to-cylindrical micellar transitions reversibly with variation in the relative water/THF ratio. The ability to form disks beginning from either THF-rich or water-rich solutions indicated that the disk morphology was thermodynamically stable and that THF was important in keeping the micellar structure from becoming kinetically frozen. The nanoassemblies were produced having low size dispersities and were stable for at least one month. Intermediate structures between disks and cylinders were also observed, indicating two distinct kinetic pathways between the two micelle structures. 相似文献
48.
Novel linear poly(NIPA‐co‐CL) copolymers have been synthesized by radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐methylene‐1,3‐dioxepane (MDO). The structure of copolymers was confirmed by 1H NMR and IR spectroscopy. Cross‐linked poly(NIPA‐co‐CL) hydrogels have also been prepared in toluene using N,N′‐methylenebisacrylamide as cross‐linking agent. The hydrogels thus obtained exhibit good temperature response and are biodegradable in the presence of proteinase K.
49.
新型水溶性膦铑络合物催化烯烃的氢甲酰化反应研究 总被引:10,自引:1,他引:10
新型水溶性膦铑络合物催化烯烃的氢甲酰化反应研究燕远勇,左焕培,金子林(大连理工大学化工学院,大连116012)关键词烯烃,水溶性膦铑络合催化剂,氢甲酰化,醛.1.前言为克服催化剂的流失和与反应产物的分离困难,近年来均相催化的一个重要进展是开发了以磺化... 相似文献
50.
Yuchuan Zhang Jiasheng Qian Zhuo KeXiangcheng Zhu Hong BiKangming Nie 《European Polymer Journal》2002,38(2):333-337
The intermolecular interactions between poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAc) in tetrahydrofuran (THF), methyl ethyl ketone (MEK) and N,N′-dimethylformamide (DMF) were thoroughly investigated by the viscosity measurement. It has been found that the solvent selected has a great influence upon the polymer-polymer interactions in solution. If using PVAc and THF, or PVAc and DMF to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+THF) or (PVAc+DMF) is less than in corresponding pure solvent of THF or DMF. On the contrary, if using PVAc and MEK to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+MEK) is larger than in pure solvent of MEK. The influence of solvent upon the polymer-polymer interactions also comes from the interaction parameter term Δb, developed from modified Krigbaum and Wall theory. If PVC/PVAc blends with the weight ratio of 1/1 was dissolved in THF or DMF, Δb<0. On the contrary, if PVC/PVAc blends with the same weight ratio was dissolved in MEK, Δb>0. These experimental results show that the compatibility of PVC/PVAc blends is greatly associated with the solvent from which polymer mixtures were cast. The agreement of these results with differential scanning calorimetry measurements of PVC/PVAc blends casting from different solvents is good. 相似文献