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51.
Summary Heterobimetallic complexes of the types [Cp2Ti(-EAr)2-M(dppe)] (ClO4)2 [(1)–(4); M, E = Ni, Te (1); Ni, Se (2); Pt, Te (3); Pt, Se (4); Ar = Ph (a), C6H4-4-Me (b), C6H4-4-OMe (c), C6H4-4-OEt (d)] and [Cp2Ti(-TeAr)2-MCl 2] [M = Pd (5), Pt (6)] were obtained by the reactions of Cp2Ti(EAr)2 with M(dppe)(ClO4)2 and M(PhCN)2Cl2, respectively. While (1), (5) and (6) are stable in the solid state as well as in solution, (2)–(4) undergo dissociation to M(dppe)(EAr)2 and Cp2Ti(ClO4)2 in solution, as shown by multinuclear (31P{1H},195Pt{1H}, 125Te{1H}) n.m.r. studies. The reaction of Cp2Ti(SeAr)2 with M(PhCN)2Cl2, however, leads to the formation of Cp2TiCl2 and a polymeric material [M(SeAr)2]
n
. 相似文献
52.
Devendra Kumar Uday Razdan Alka D. Gupta 《Journal of polymer science. Part A, Polymer chemistry》1992,30(7):1477-1487
Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl) dimethylsilane dianhydride (SIDA), 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis(3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3′, 4,4′-tetracarboxylichenzophen+ne dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271°C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance (1H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers. Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410–400°C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermallystable, tough polymers. 相似文献
53.
S. C. Gupta B. B. Tak N. K. Mathur C. K. Narang 《Journal of Radioanalytical and Nuclear Chemistry》1993,170(1):3-8
Polyamino group-containing resins act both as chelating ion exchangers and weakly basic anion exchangers depending upon the species in contact in the solution. In the present work, ion exchangers based on polyamine incorporated polysaccharides (cellulose and galactomannan or guaran) have been used for removal of radioisotopes of185W as WO
4
2–
,99Mo as MoO
4
2–
and125Sb as Sb3+ from their separate aqueous solutions. These chelating anion exchangers have been synthesized by reaction of polysaccharides with epichlorohydrin followed by the respective polyamines as nucleophiles in a strongly alkaline medium. WO
4
2–
and MoO
4
2–
are adsorbed from their aqueous solutions through anion exchange process by chloride form of cellulose-triethylenetetraamine (cellulose-trien), cellulose-tetraethylenepentaamine (cellulose-tetren), guaran-triethylenetetraamine (guar-trien) and guar-tetraethylenepentaamine (guar-tetren) weakly basic anion exchangers. Guar-tetren chelating polymer has been found to be highly selective for125Sb isotopes presumably due to the presence of chelating cis-hydroxy and tetren groups in the galactomannan matrix. 相似文献
54.
Priti Gupta 《Tetrahedron letters》2005,46(38):6571-6573
A short and practical enantioselective synthesis of tarchonanthuslactone has been achieved in high diastereomeric excess using iterative Jacobsen’s hydrolytic kinetic resolution and ring closing metathesis as the key steps. 相似文献
55.
A simple, rapid, cost-effective and accurate high performance thin layer chromatographic method has been developed for quantification
of valerenic acid in Valeriana jatamansi and Valeriana officinalis which is one of the stable compounds of Valeriana officinalis and designated as a key marker compound. Valerenic acid makes substantial contribution to the sedative and spasmolytic activity
of the essential oil and extract of Valeriana officinalis. Separation and quantification was achieved by HPTLC using ternary mobile phase of hexane: ethyl acetate: acetic acid (80:20:0.5
v/v) on precoated silica gel 60F254 aluminium plates and densitometric determination was carried out after derivatization with anisaldehyde-sulphuric acid reagent
at 700 nm, in absorption-reflectance mode. The calibration curves were linear in the range of (500 ng–2.5 μg). This is the
first HPTLC report for the identification and quantification of valerenic acid in Valeriana jatamansi and Valeriana officinalis. 相似文献
56.
Simulation of the Adhesion of Particles to Surfaces 总被引:1,自引:0,他引:1
The removal of micrometer and submicrometer particles from dielectric and metal films represents a challenge in postchemical mechanical polishing cleaning. Proper modeling of the adhesive force between contaminant particles and these films is needed to develop optimal solutions to postchemical mechanical polishing cleaning. We have previously developed and experimentally validated a model to describe the adhesion between spherical particles and thin films. This simulation expands previous models to characterize the adhesive interaction between asymmetrical particles, characteristic of a polishing slurry, and various films. Our simulation accounts for the contact area between particles and substrates, as well as the morphology of the surfaces. Previous models fail to accurately describe the contact of asymmetrical particles interacting with surfaces. By properly accounting for nonideal and geometry and morphology, the simulation predicts a more accurate adhesive force than predictions based upon an ideal van der Waals model. The simulation is compared to experimental data taken for both semi-ideal particle-substrate systems (polystyrene latex spheres in contact with silicon films) and asymmetrical systems (alumina particles in contact with various films). Copyright 2001 Academic Press. 相似文献
57.
Attempts to cyclise o-chlorophenyl benzyl ether, sulphide, sulphoxide and sulphone by treatment with KNH2/NH3 were unsuccessful. Similar reaction of 1-(o-chlorophenyl)-2,2-diphenylethane led to amination whereas α-(o-chlorobenzyl)phenylacetic acid gave a dihydrocoumarin. Reaction of 4- and 2-(o-chlorophenethyl)-pyridines, however, afforded products comprising benzisoquinolines and 1-pyridylbenzocyclobutenes. 相似文献
58.
59.
P. B. Ruikar M. S. Nagar M. S. Subramanian K. K. Gupta N. Varadarajan R. K. Singh 《Journal of Radioanalytical and Nuclear Chemistry》1995,201(2):125-134
The extraction of plutonium(IV), uranium(VI), zirconium(IV), europium(III) and ruthenium(III) with -pre-irradiated n-dodecane solutions of methylbutyl substituted hexanamide (MBHA), octanamide (MBOA) and decanamide (MBDA) from 3.5M HNO3 has been studied as a function of absorbed dose up to 184×104 Gray. The distribution ratios (Kd) of uranium(VI) decreased gradually up to a dose of 50×104 Gray and became almost constant thereafter, while ruthenium(III) and europium(III) were not extracted in the entire dose range studied. The Kd values of Pu(IV) decreased gradually up to 10×104 Gray, for MBOA, and 30×104 Gray for MBHA and MBDA and then increased up to a dose of 72×104 Gray, indicating the synergistic effect of radiolytic products at higher doses. The extraction of zirconium(IV) was found to increase gradually up to 72×104 Gray. However, the steep fall in Kd values of plutonium(IV), zirconium(IV) beyond a dose of 72×104 Gray was atrributed to third phase formation. The radiolytic degradation of amides was monitored by quantitative IR spectroscopy and was found to follow the order MBOA>MBDA>MBHA at 184×104 Gray having the amines and carboxylic acids as the main radiolytic products. 相似文献
60.
Magnesium formate dihydrate has been synthesized by the action of formic acid on anhydrous magnesium oxide. This product analysed as Mg(COOH)2 · 2H2O. Its mode of thermal decomposition has been studied by thermal methods of analysis including simultaneous DTA/mass spectrometry. Nitrogen adsorption surface area of the solid products at various stages of its decomposition have been obtained. X-Ray diffraction and scanning electron micrographs have also been used to interpret the results. The decomposition of magnesium formate took place in three stages, which includes a phase change, at 265°C. The endotherm at 430°C changed to an exotherm in the presence of air; it corresponded to the decomposition of a new anhydrous phase of magnesium formate. The effect of the sample holder and changing atmospheres on the DSC analysis has been investigated. A scheme is presented for the thermal decomposition. 相似文献