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991.
The novel acid carbon has been synthesized successfully via one-step hydrothermal carbonization. The acid carbon owned the morphologies of the spheres with smooth surfaces and the acidity of 2.4 mmol/g. The catalytic activities of the novel acid carbon were investigated through oxathioacetalization. The results showed that the acid carbon owned high activity for the reactions with the average yields over 95%. The advantages of high activity, stability, reusability, low cost for the simple synthetic procedure and wide application to various carbonyl compounds made the acid carbon one of the best choices for the reactions. 相似文献
992.
Increase of pH induced by Cu(2+)-catalyzed Fenton reaction promoted ring-opening of triazole-linked fluorescein lactone, which enabled selective "turn-on" fluorescent detection of Cu(2+), along with ultralow naked-eye detection limit down to 200 nM. 相似文献
993.
Biological mineral generation via an amorphous precursor is a topic of great current interest. Various factors such as the temperature, solution composition and presence of organic molecules can influence this important inorganic process. Here we demonstrate that this mineral transformation can actually readily be regulated by solution viscosity, a fundamental but often overlooked property. In our experiment, amorphous calcium carbonate (ACC), a key model compound in biomimetic mineralization studies, is synthesized and dispersed into inert dispersants with different viscosities and the crystallization process is examined by using FT-IR spectroscopy and XRD. It is found that the inhibition of the transformation of ACC becomes more significant with increasing fluid viscosity. This phenomenon can be explained by the differences in ion diffusion in different media. Furthermore, the resulting crystals always have different morphologies and size distributions although they all have the calcite structure. This study implies that the importance of the fluid medium cannot be ignored in building a complete understanding of biological control of biomimetic crystallizations. 相似文献
994.
By means of an electrochemical study, the influence of arsenic, antimony and cobalt on cathodic polarization in the zinc electrowinning process, the associated kinetic equations and parameters, and the polarization mechanism have been studied. The results show that the experimental values of the kinetic parameters are in accord with the theoretical values in the ZnSO4/H2SO4 solution with a single impurity is added. In contrast, the charge transfer coefficient α is smaller than the theoretical value in the ZnSO4/H2SO4 solution when the three impurities are added together. 相似文献
995.
LinHua Xie JianBin Lin XiaoMin Liu Wei Xue WeiXiong Zhang ShuXia Liu JiePeng Zhang XiaoMing Chen 《中国科学:化学(英文版)》2010,53(10):2144-2151
Solvothermal reactions of 1,3,5-benzenetricarboxylic acid (H3btc) with cadmium acetate or zinc acetate yielded two compounds formulated as (Me2NH2)[Cd(btc)]·DMA (1) (btc = 1,3,5-benzenetricarboxylate, DMA = N,N-dimethylacetamide) and (Me2NH2)[Zn(btc)]·DMF (2) (DMF = N,N-dimethylformamide). Both are 3-D frameworks with the rutile topology, which are constructed from six-connected dimeric metal cores and three-connected btc linkers. The solvent molecules and counter cations are located in the 1-D channels of the frameworks. A slight difference between the two compounds is the different connectivity modes of the metal atoms with the carboxylate groups of the ligands. However, this slight difference results in distinct flexibilities of the two frameworks. Variable-temperature powder X-ray diffraction studies revealed that the framework of 1 collapses when heated at 180 °C with loss of the guest species, but compound 2 undergoes two structural transformations below 380 °C. Thermogravimetry-infrared spectroscopy analysis for 2 showed that the two structural transformations are induced by separate losses of solvent molecules and counter cations, and that the dimethylammonium cations are eliminated as neutral dimethylamine molecules. IR spectroscopy demonstrated that the protons are transferred from the counter cations onto the uncoordinated carboxylate oxygen atoms on the channel walls. Sorption and proton conduction studies have also been performed for the compounds. 相似文献
996.
Guohai Xu Yongrong Xie 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(8):m201-m203
In the title compound, [Cd(C8H4O4)(C10H8N2O2)(H2O)]n, (I), each CdII atom is seven‐coordinated in a distorted monocapped trigonal prismatic coordination geometry, surrounded by four carboxylate O atoms from two different benzene‐1,4‐dicarboxylate (1,4‐bdc) anions, two O atoms from two distinct 4,4′‐bipyridine N,N′‐dioxide (bpdo) ligands and one water O atom. The CdII atom and the water O atom are on a twofold rotation axis. The bpdo and 1,4‐bdc ligands are on centers of inversion. Each crystallographically unique CdII center is bridged by the 1,4‐bdc dianions and bpdo ligands to give a three‐dimensional diamond framework containing large adamantanoid cages. Three identical such nets are interlocked with each other, thus directly leading to the formation of a threefold interpenetrated three‐dimensional diamond architecture. To the best of our knowledge, (I) is the first example of a threefold interpenetrating diamond net based on both bpdo and carboxylate ligands. There are strong linear O—H...O hydrogen bonds between the water molecules and carboxylate O atoms within different diamond nets. Each diamond net is hydrogen bonded to its two neighbors through these hydrogen bonds, which further consolidates the threefold interpenetrating diamond framework. 相似文献
997.
Luminol-type compounds can be used as chemiluminescent (CL) derivatization reagents for amines, carboxylic acids and protein. Copper chelate diperiodatocuprate(III) (K5[Cu(HIO6)2], DPC) was synthesized by complexation of copper at trivalent oxidation state and periodate in a strong basic medium. It was found that DPC can greatly enhance the reaction between luminol-type compounds and H2O2 to produce very strong CL emission. Based on this fact, a rapid CE method combined with high-sensitive end-column CL detection was established to simultaneously analyze luminol and N-(4-aminobutyl)-N-ethylisoluminol (ABEI) with wide concentration range of 3.0-300 nmol/L in 5 min. The RSDs of the signal intensity and the migration time were less than 3.9 and 7.0% for a standard sample containing 100 nmol/L luminol and ABEI (n=5), respectively. The investigation implies that DPC is a promising sensitizer for CE-CL detection of a great variety of biomolecules and drugs in biological samples after derivatization using luminol derivatives. 相似文献
998.
We described hereby an instance of diastereoselective silver-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with imine compounds. This new method provided synthetically useful, highly substituted tetrahydroimidazole derivatives with efficiency and high diastereoselectivity. We can conveniently obtain fluorinated dihydroimidazole, imidazole, and diamino esters through simple modification. 相似文献
999.
The asymmetric domino Michael-S(N)2 reaction of various 1,3-dicarbonyl compounds to α-bromonitroalkenes is described for the first time, employing readily available cinchona-derived bifunctional thioureas as organocatalysts. The novel transformations were highly regio-, chemo-, diastereo-, and enantioselective, which simultaneously gave the chiral tricyclic 2,3-dihydrofurans, bicyclic 2,3-dihydrofurans, and tetrasubstituted 2,3-dihydrofurans with two vicinal chiral carbon centers. 相似文献
1000.
Xin‐Gang Xie Dr. Xun‐Wei Wu Dr. Hing‐Ken Lee Dr. Xiao‐Shui Peng Prof. Dr. Henry N. C. Wong Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(23):6933-6941
Plakortone B is a naturally occurring bicyclic[3.3.0]furanolactone compound with attractive bioactivities. Although the relative configuration of plakortone B’s central core had been established by NMR spectroscopic methods, the absolute configuration of its four stereocenters remained unknown. In the present paper, all four possible isomers of plakortone B were synthesized and one of these molecules was found to be identical with the natural plakortone B on the basis of 1H, 13C NMR spectra and specific rotation comparisons. Thus, the absolute configuration of the natural plakortone B was determined to be (3S,4S,6R,10R). 相似文献