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861.
Zong Yuan Chen Wei Zhang 《中国化学快报》2007,18(12):1443-1446
A simple method for the oxidative aromatization of Hantzsch 1,4-dihydropyridines to the corresponding pyridines is achieved by using hydrogen peroxide as green oxidant and acetic acid as catalyst in aqueous solution. 相似文献
862.
Balkis Al‐Saleh Morsy Ahmed El‐Apasery Rasha Safwat Abdel‐Aziz Mohamed Hilmy Elnagdi 《Journal of heterocyclic chemistry》2005,42(4):563-566
The 3‐anilinoenones 3a,b were prepared from the corresponding 3‐dimemyl‐aminopropenones. The reactivity of 3a,b towards a variety of carbon and nitrogen nucleophiles as well as naphthoquinones is reported. 相似文献
863.
864.
Zr柱撑蒙脱土上负载稀土铈及铜铈催化剂的制备与表征 总被引:1,自引:0,他引:1
The Zr-pillaraed montmorillonite supported Ce and Cu-Ce catalysts were prepared by impregnation method. The performance of the catalysts was evaluated via the catalytic oxidation of volatile organic compounds (acetone, ethyl acetate, and toluene). The results showed that after supporting with Ce and Cu-Ce, the catalysts had a better reducibility. Moreover, the surface areas of the samples were increased. In addition,it was found that the Zr-pillared montmorillonite supported Cu-Ce catalysts had a higher activity and the reaction temperature decreased by 150~200 ℃ compared with the sample without Cu-Ce modification. 相似文献
865.
胶束电动毛细管色谱半导体激光诱导荧光测定单胺类神经递质 总被引:3,自引:0,他引:3
建立了用半导体激光诱导荧光结合胶束电动毛细管色谱测定单胺类神经递质——去甲肾上腺素和多巴胺的高灵敏分析方法。考察了青色素衍生物 ( Cy5 )对去甲肾上腺素和多巴胺的衍生条件。在优化条件下 ,去甲肾上腺素和多巴胺在 3× 1 0 - 8~ 5× 1 0 - 6 mol/L浓度范围内与荧光强度呈良好的线性关系。去甲肾上腺素和多巴胺的检出限分别为 5 .9× 1 0 - 9、 5 .4× 1 0 - 9mol/L。方法简便、灵敏、样品用量少 ,可用于痕量单胺类神经递质分析 相似文献
866.
the interaction of hemin with chloroquine,quinine and quinidine was investigated in 50% water-propylene glycol mixture at pH=9,8.1,7.4 and 6.8using a spectrophotometric method.The data could be well fitted into a model consistent with the formation of a 1:1 complex between the reacting partners.In addition,the results indicated that hemin complexed more strongly with quinidine than with chloroquine and quinine,and the binding constants were pH-dependent.Moreover,it was proved that the water-propylene glycol mixture is well suitable to the study of the systems containing hemin and quinolinebased drugs. 相似文献
867.
Ingo Hartenbach Falk Lissner Tanja Nikelski Steffen F. Meier Helge Müller‐Bunz Thomas Schleid 《无机化学与普通化学杂志》2005,631(12):2377-2382
About Lanthanide Oxotantalates with the Formula MTaO4 (M = La – Nd, Sm – Lu) Besides being a by‐product of solid state syntheses in tantalum ampoules the lanthanide(III) oxotantalates of the formula MTaO4 can be easily prepared by sintering lanthanide sesquioxide M2O3 and tantalum(V) oxide Ta2O5 with sodium chloride as flux. Under these conditions two structure types emerge depending upon the M3+ cationic radius. For M = La – Pr the MTaO4‐type tantalates crystallize in the space group P21/c with lattice constants of a = 762(±1), b = 553(±4), c = 777(±4) pm, β = 101(±1)° and four formula units per unit cell. With M = Nd, Sm – Lu, the monoclinic cell dimensions (space group P2/c) shrink to the lattice constants like a = 516(±9), b = 551(±9), c = 534(±9) pm, β = 96.5(±0.3)° and there are only two formula units present. Both structures show a coordination sphere of eight oxygen atoms for the lanthanide trications shaped as distorted square antiprism for the structure with the larger lanthanides (in the following referred to as A‐type) and as trigonal dodecahedron for the structure with the smaller ones (called as B‐type in the following). The coordination environment about the Ta5+ cations can be described as a slightly distorted octahedron (CN = 6) for the A‐type structure of MTaO4 and a heavily distorted one (CN = 6) for the B‐type. The difference between the two types results from the interconnection of these [TaO6]7? octahedra. Whereas they are connected via four vertices to form corrugated layers according to parallel the bc‐plane in the A‐type, the octahedra of the B‐type MTaO4 structure share edges to built up zig‐zag chains along the c axis. 相似文献
868.
B. Montanari B. Civalleri C. M. Zicovich‐Wilson R. Dovesi 《International journal of quantum chemistry》2006,106(7):1703-1714
The equilibrium structural parameters, high‐ and low‐frequency dielectric tensors, Born effective charges, and Γ‐point vibrational frequencies of bulk Al2O3 corundum are calculated by using the periodic, ab initio program CRYSTAL, which adopts an all‐electron Gaussian‐type basis set. The effect of basis set and the performance of three different functionals, i.e., LDA, PW91, and B3LYP, are discussed. The mean absolute deviation from the measured frequencies is as small as 7 cm?1 for both the LDA and B3LYP functionals, indicating that these functionals perform extremely well in this case. The mean absolute deviation increases to 18 cm?1 when the PW91 functional is used. All three functionals reproduce the equilibrium geometry of corundum to a high level of accuracy, with LDA and B3LYP outperforming PW91 slightly. The comparison of the current all‐electron calculations with previous plane‐wave, pseudo‐potential calculations shows an overall similar performance. The results of isotopic substitution for both Al and O are also presented. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献
869.
Superabsorbent hydrogel composites 总被引:1,自引:0,他引:1
A new cost‐effective approach to enhance gel strength of superabsorbent hydrogels was invented. Superabsorbent hydrogel composites (SHCs) were prepared through an optimized rapid solution polymerization of concentrated partially neutralized acrylic acid in the presence of a crosslinking agent under normal atmospheric conditions. Kaolin was used as an inorganic component in the polymerization process to strengthen the hydrogel products. FT‐IR spectroscopy was used to confirm grafting of acrylic chains on to the surface of kaolin particles. Morphology of the products was studied by scanning electron microscopy (SEM). Compared with the kaolin‐free hydrogel (control), kaolin caused a reduced equilibrium swelling and swelling rate as low as 17–31% and 19–29%, respectively. Kaolin, however, resulted in enhanced gel strength as high as 21–35% compared to the control. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study thermal properties of the composites. The SHCs exhibited higher thermal stability than the control. Meanwhile, changes in certain thermal transitions reconfirmed the chemical interaction of the acrylic chain with kaolin. These thermostabilized strengthened superabsorbent hydrogels may be considered as good candidates for agricultural application to retain more water under soil pressure. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
870.
Fatehy M. Abdel‐Haleem Azza Salah Mahmoud S. Rizk Hussein Moustafa Mikhael Bechelany Ahmed Barhoum 《Electroanalysis》2019,31(4):778-789
Thiourea derivative‐based carbon paste electrode (TUD1‐CPE) was constructed as a potentiometric sensor for the determination of salicylate anion in pharmaceutical formulations, Aspocid® and Aspirin®. The optimized CPE contained 45.5 % graphite, 0.5 % reduced graphene oxide (rGO), 46.0 % nitrophenyl octyl ether (NPOE) plasticizer, 5.0 % TUD1 ionophore, and 3.0 % tridodecylmethyl ammonium chloride as additive. The incorporation of NPOE of high dielectric constant, and rGO in electrode caused better performance of the sensor; Nernstian response of 59.0 mV decade?1 in the concentration range of 10?1–10?5 mole L?1, a detection limit of 1×10?5 mole L?1 in a very short response time of 6 seconds. The prepared sensor showed high selectivity against similar anions (i. e. , benzoate, I?, SCN?). Selectivity was confirmed by calculating the formation constant (Kβ) using sandwich membrane method, where Kβ for TUD1‐salicylate is 100.43. Theoretical calculations at DFT‐B3LY/6‐31G** level of theory were performed to find interaction mechanism, Energies of HOMO and LUMO orbitals, non‐linear optical (NLO) properties (the electronic dipole moment (μ), first‐order hyperpolarizability (β), the hyper‐Rayleigh scattering (βHRS) and the depolarization ratio (DR)), and other global properties; these calculations showed lower values of β and DR, higher value of βHRS, and the shortest lengths of the four N?H bonds between TUD1 and salicylate which confirm their strong complexation and salicylate‐selectivity. Also, all the studied anion‐TUD1 exhibited relatively high NLO properties, and these results were considered as a preliminary study for investigating new types of NLO bearing materials. The sensors were applied successfully for the determination of salicylate anion in Aspocid® and Aspirin®. 相似文献