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941.
Enthalpies of dissolution of benzo-15-crown-5 ether (B15C5) in mixtures of acetonitrile with water and in solutions of NaI and NaBPh4 (I=0.05 mol dm–3) in these mixtures were measured at 298.15 K. From the obtained results and appropriate literature data, the thermodynamic functions of B15C5/Na+ complex formation in acetonitrile-water mixtures were determined. The enthalpies of transfer of the complex B15C5/Na+ from pure acetonitrile to the examined mixtures were calculated and are discussed. 相似文献
942.
中性红作试剂荧光光度法测定亚硝酸根 总被引:3,自引:1,他引:3
研究了在盐酸介质中NO^-2与中性红的亚硝化反应。结果表明,在0.048mol/L的盐酸介质中,NO^-2与中性红反应生成无荧光的物质,NO^-2在40-240μg/L,范围内与荧光猝灭程度成正比,常见的共存离子不干扰其测定。所拟方法用于水样中NO^-2的测定,结果满意。 相似文献
943.
Lizhuang Zou Buxing Han Haike Yan K.L. Kasperski Yuming Xu L.G. Hepler 《Journal of colloid and interface science》1997,190(2):472
The enthalpies of adsorption and the isotherms for adsorption of naphthenic acid onto Na-montmorillonite, Na-kaolinite, and Na-illite were studied by means of calorimetry and the static method at 298.15 K. The results show that the enthalpies of adsorption and saturated adsorption amounts of naphthenic acid on different clays change in the order Na-montmorillonite > Na-illite > Na-kaolinite. The interaction between naphthenic acid and clays is discussed. 相似文献
944.
制备了一系列V,Ag,Ni原子比不同的三元氧化物,应用TPD-MS技术研究了样品表面氧的性质,并测定了甲苯选择性氧化生成苯甲醛的催化活性。实验结果表明,样品表面存在有多种吸附的氧物种。在脱附温度<900℃:当Ni含量对Ag(或V)的原子比为0.25或0.50时,仅在低温处出现有表面的O^-和O^2^-两种氧物种的脱附峰;当Ni含量对Ag(或V)的原子比增高到>0.75时,除有表面的O^-和O^2^ 相似文献
945.
以紫外光谱、荧光光谱、粘度法和凝胶电泳方法研究了全反式维甲酸合钇(Ⅲ)配合物与DNA的作用。结果表明,该配合物能在生理条件下比配体和金属离子更有效地切割质粒DNA,体系离子强度和pH值的变化对配合物的切割活性有较大影响,自由基捕捉剂的加入不影响配合物的切割活性。该配合物对DNA的切割可能通过水解机理进行。该配合物可使DNA的粘度增加,使EB-DNA体系的荧光强度和DNA溶液的紫外吸收强度降低。据此推断,该配合物主要以嵌入方式与DNA作用。 相似文献
946.
Gostev F. E. Petrukhin A. N. Titov A. A. Shienok A. I. Marevtsev V. S. Sarkisov O. M. 《Russian Chemical Bulletin》2003,52(3):557-561
Intramolecular processes in electronic-excited states of 2,4,5-triarylimidazole molecules were studied by femtosecond laser spectroscopy. Experiments were carried out with two types of compounds, namely, those experiencing intramolecular proton transfer and two model compounds in which it is impossible. Schemes of the processes studied were proposed and the characteristic rate constants were determined. The excited-state intramolecular proton transfer (ESIPT) in the molecules with planar structure of the reaction center is a very fast process (100 fs). If the reaction center has a nonplanar structure and, hence, the intramolecular hydrogen bond is weakened, the ESIPT time is determined by the time of conformational rearrangement of the molecule. 相似文献
947.
A new approach to calculating the equilibrium characteristics of the adsorption of noble gases on the amorphous surfaces of
adsorbents was developed and applied to the Ar−TiO2(rutile) system. Intermolecular adsorbate-adsorbate interactions are taken into account for the nearest neighbors in the quasi-chemical
approximation. The lattice energy parameters of all interactions of the model are determined from the Lennard-Jones potential
(12-6). The formation of amorphous TiO2(rutile) surface includes completion of the surface layers and partial removal of the surface oxygen ions. The quality of
the amorphization procedure was confirmed by the experimentally measured heats and isotherms of adsorption of the system under
study.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1109–1118, June, 1997. 相似文献
948.
Deprotonated Dithiocarbamic Acid Esters as Thiolate S-Donor Ligands. Structures of Ph(H)NC(S)SMe, Co(PhNC(S)SMe)3, and Cu6(PhNC(S)SMe)6 The reaction of N-phenyl-S-methyldithiocarbamate, PhN(H)C(?S)SMe, ( 1 ) with cobalt(II) and copper(II) salts yields the monomeric compound CoIII(PhNC(S)SMe)3 ( 2 ) and the hexameric compound Cu6I(PhNC(S)SMe)6 ( 3 ). These complexes contain the negatively charged imino-thiolate ligand PhN?C(? S)SMe, which has been formed by deprotonation of 1 . The crystal structures of 1 – 3 have been determined. 1 forms centrosymmetrical dimers through N? H …? S bridge bonds, the conformation in the solid state and in solution is Z,E′. CoIII shows in 2 a trigonal-antiprismatic coordination, with the ligands acting as N,S-chelates. 3 contains an octahedral Cu6-core with Cu …? Cu-distances ranging from 276.3(5) to 305.7(4) pm. Each copper center is trigonally coordinated to one nitrogen and two sulfur atoms of three different ligands. Crystal data: 1 , triclinic, space group P1 , a = 590.5(6), b = 869.0(1), c = 968.5(9) pm, α = 67.29(8), β = 78.44(8), γ = 81.64(9)°, Z = 2, 1 775 reflections, R(Rw) = 0.0317(0.032). 2 , orthorhombic, space group Pbca, a = 978.0(2), b = 1 842.9(4), c = 3 059.7(6) pm, Z = 8, 1 129 reflections, R(Rw) = 0.0997(0.0886). 3 , monoclinic, space group P21/c, a = 1 363.1(3), b = 1 342.8(3), c = 1 671.9(3) pm, β = 103.48°, Z = 2, 1 374 reflections, R(Rw) = 0.0708(0.0617). 相似文献
949.
Tadatomi Nishikubo Atsushi Kameyama Jun Yamashita Masao Tomoi Wakichi Fukuda 《Journal of polymer science. Part A, Polymer chemistry》1993,31(4):939-947
The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO2) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO2 proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc. 相似文献
950.