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41.
[reaction: see text] A tin(II) chloride-mediated short, efficient, and practical regioselective synthesis of biheterocyclic 5,6-dihydro-quinazolino[4,3-b]quinazolin-8-ones with three-point diversity is reported. A one-step reductive transformation of 2-(2-nitrophenyl)-3H-quinazolin-4-one in various alcohols furnished the desired tetracyclic product in good yields with high purity. 相似文献
42.
R. Verma J. Arunachalam S. Gangadharan J. C. Vyas G. P. Kothiyal M. K. Gupta 《Fresenius' Journal of Analytical Chemistry》1992,344(6):261-264
Summary Coprecipitation behaviour of As, Au, Co, Cr, Cu, Eu, Fe, Ir, La, Lu, Mn, Mo, Nb, Ni, Pd, Pt, Sb, Sc, Ta, W, Zn and Zr during precipitation of hydrous oxide of niobium from lithium niobate was investigated. The matrix was dissolved in HF-HNO3, evaporated to dryness and niobium was precipitated from HNO3-H2O2 medium. The recovery studies were made using radiotracers. A radiochemical separation scheme based on group precipitation has been developed for the determination of Au, Co, Cr, Cu, Fe, Mn, Ni, Pd, Pt, Zn, Zr and rare earth elements. The method was applied to the analysis of lithium niobate. This analysis has provided fruitful information for improving the quality of the crystal. 相似文献
43.
Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham Kannappan Santhakumar 《Transition Metal Chemistry》2006,31(2):250-255
A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)2(A)X]2+ and cis-α-[Cr(trien)(A)X]2+ (A = Dodecyl or Cetylamine; X = F−, Cl−, Br−) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous
solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution
were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the
temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ Gm0, Δ Hm0 and Δ Sm0). 相似文献
44.
Kannappan Santhakumar Narayanasamy Kumaraguru Sankarlingam Arunachalam Mahadevimanglam Narayanasamy Arumugham 《Transition Metal Chemistry》2006,31(4):475-481
The kinetics and mechanism of iron(II) reduction of cis- α-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically
in an aqueous acid medium by following the disappearance of CoIII using an excess of the reductant under pseudo-first-order conditions: [FeII = 0.25 mol dm−3, [H+ = 0.1 mol dm−3, [μ = 1.0 mol dm−3 ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid
independence in the range [H+ = 0.05−0.25 mol dm−3. The second order rate constant increased with CoIII concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of [FeII], [H+] and [ μ] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of
Fe2+(aq) with CoIII complex proceeds by an inner-sphere mechanism. 相似文献
45.
Vapour phase dissolution (VPD) has been used for the dissolution of high purity arsenic through acid vapours generated by aquaregia mixture, prior to trace element characterization. Trace impurities in As were determined by employing ion-exchange and volatilization methodologies for quantitative separation of the As matrix. After dissolving the As matrix through VPD procedure, sample solution in 0.1 M HF medium was loaded on Dowex-50WX8. The sorbed elements were then eluted first with a 20 ml aliquot of 4 M HNO3 followed by another 10 ml of 6 M HNO3 for the elution of REE (La, Ce, Gd and Lu). In the volatilization procedure, arsenic was removed from H2SO4 medium as volatile bromide by three successive additions of HBr at a temperature of about 220 °C. The trace element determinations were carried out by ICP-QMS. In both the matrix separation procedures namely on Dowex-50WX8 in 0.1 M HF medium and volatilization from H2SO4+HBr medium showed that the removal of arsenic matrix was nearly quantitative (>99.99%). The recoveries of trace elements were found to be >95%. Good agreement was obtained for many elements in both the procedures. The VPD approach provides considerable reduction of the process blank levels for all the elements when compared with conventional open dissolution approach. The subsequent ion-exchange or volatilization steps, contribute more to the overall process blanks. 相似文献
46.
J. Arunachalam C. Mohl P. Ostapczuk H. Emons 《Fresenius' Journal of Analytical Chemistry》1995,352(6):577-581
The recovery of trace elements of ecotoxic importance has been studied on certified soil and sediment reference samples after pressurized digestions with HNO3, HNO3+HF and HNO3+HCl+HF mixtures, respectively. The acid digests have been analyzed by ICP-MS. The results indicate that digestion with nitric acid alone is satisfactory for the recovery of As, Cd, Co, Cu and Zn. Cr and Pb showed lower recoveries with HNO3 alone but addition of HF improved their extraction. With appropriate corrections, ICP-MS can be used for the routine analysis of soils and sediments. These digestion procedures, evaluated based on reference samples, have been used for the trace element characterization of soil samples from the German Environmental Specimen Bank. 相似文献
47.
R. Senthil Kumar S. Arunachalam V.S. Periasamy C.P. Preethy A. Riyasdeen M.A. Akbarsha 《Polyhedron》2008
The novel water-soluble polymer–cobalt(III) complex samples, cis-[Co(phen)2(BPEI)Cl]Cl2 · 4H2O (phen = 1,10-phenanthroline, BPEI = branched polyethyleneimine), with different amounts of cobalt complex content in the polymer chain, were prepared by ligand substitution method in water–ethanol medium and characterized by Infra-red, UV–Vis, 1H NMR spectral and elemental analysis methods. The interaction of these polymer–cobalt(III)-phenanthroline complex samples with calf thymus DNA has been explored using electronic absorption spectroscopy, emission spectroscopy and gel electrophoresis techniques. The presence of multiple small size molecular binding sites, namely, the cobalt(III)–phenanthroline complex moieties, and free amino groups in a single big sized polymer molecule enhanced both the electrostatic and/or van der Waals interaction and partial intercalative bindings with calf thymus DNA. The antitumor activity of a sample of polymer–cobalt(III) complex was determined using HEp-2 cell line and different cell death indicator stains and MTT assay. Many of the cultured HEp-2 cells treated with this complex suffered loss of viability and death mostly through apoptosis as evidenced by the nuclear and cytoplasmic morphology. 相似文献
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