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排序方式: 共有477条查询结果,搜索用时 343 毫秒
1.
Tapasi Chand Laxmikanta Khamari Deepak Chopra Saptarshi Mukherjee Manmohan Kapur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(43):e202200723
A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization. 相似文献
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Polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA) and polybutyl methacrylate (PBuMA) containing ferric chloride and ferrous sulphate as stabilisers, were prepared by free radical polymerization. Mössbauer spactra of ferrous sulphate stabilised polymers don't show any change in the value of isomer shift (1.30 mm/s) while quadrupole splitting values are quite different from those for pure ferrous sulphate. This indicates that environment of Fe2+ moiety changes in polymers and thus stabilises the polymers. In case of ferric chloride stabilised polymers the isomer shift values don't differ significantly for different polymethacrylates but quadrupole splitting values increase from polymethyl methacrylate to polybutyl methacrylate. The TGA analysis shows that the inclusion of iron salts stabilises the polymers by 40°C (approx.) and at higher temperatures α-Fe2O3 is formed. 相似文献
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A. B. Deshpande S. M. Kale S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1973,11(6):1307-1315
Polymerization of methyl methacrylate has been studied with the chromium acetylacetonate–triisobutyl aluminum catalyst system in benzene medium at 40°C. These studies have been carried out at an Al/Cr ratio of 12 to compare the behavior with the previously studied chromium acetyl acetonate–triethyl aluminum catalyst system. The enhanced yield and gelling of polymer suggests a free-radical mechanism of polymerization. Further, the kinetics of polymerization and the heterotactic structure of polymer as determined by NMR examination have led to confirmation of the freeradical mechanism of polymerization of methyl methacrylate by an excess of triisobutylaluminum in the presence of catalyst complex. 相似文献
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Nikhil M. Kriplani David P. Nackashi Christian J. Amsinck Neil H. Di Spigna Michael B. Steer Paul D. Franzon Ramon L. Rick Gemma C. Solomon Jeffrey R. Reimers 《Chemical physics》2006
Two efficient, physically based models for the real-time simulation of molecular device characteristics of single molecules are developed. These models assume that through-molecule tunnelling creates a steady-state Lorentzian distribution of excess electron density on the molecule and provides for smooth transitions for the electronic degrees of freedom between the tunnelling, molecular-excitation, and charge-hopping transport regimes. They are implemented in the fREEDA™ transient circuit simulator to allow for the full integration of nanoscopic molecular devices in standard packages that simulate entire devices including CMOS circuitry. Methods are presented to estimate the parameters used in the models via either direct experimental measurement or density-functional calculations. The models require 6–8 orders of magnitude less computer time than do full a priori simulations of the properties of molecular components. Consequently, molecular components can be efficiently implemented in circuit simulators. The molecular-component models are tested by comparison with experimental results reported for 1,4-benzenedithiol. 相似文献
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Sunit S. Dixit A. B. Deshpande S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1970,8(5):1289-1297
Methyl methacrylate was polymerized at 40°C with the VCl4–AlEt3 catalyst system in n-hexane. The rate of polymerization was proportional to the catalyst and monomer concentration at Al/V ratio of 2, indicating a coordinate anionic mechanism of polymerization. NMR spectra were further used to confirm the mechanism of polymerization and stability of active sites responsible for isotacticity. 相似文献
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A new method is presented for the analysis of 17[small beta]-estradiol in bovine urine. After deconjugation, the sample is cleaned up using an OASIS[trade mark sign] HLB disposable cartridge and extracted into 1-chlorobutane. The hormone is derivatized using pentafluorobenzoyl chloride. The derivatized estradiol is quantitated using gas-chromatography negative-ion chemical ionization mass spectrometry. Calibrations, obtained using spiked blank urine, are linear in the range of 100-1000 pg mL(-1) with CC[small alpha] approximately 170 pg mL(-1) and CC[small beta] of 287 pg mL(-1). Recoveries are in the range of 80 to 130%. The method is rugged, rapid and sensitive when compared to other hormone methods. 相似文献
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Sunit S. Dixit A. B. Deshpande S. L. Kapur 《Journal of polymer science. Part A, Polymer chemistry》1971,9(5):1167-1172
The polymerization of acrylonitrile with the homogeneous catalyst system of VCl4–AlEt3 in acetonitrile at 40°C has been investigated. The rate of polymerization is found to be first-order with respect to monomer and inversely proportional to the catalyst concentration. The overall activation energy for this catalyst system is 10.97 kcal/mole. The inverse proportionality of rate of polymerization with the catalyst concentration is attributed to the permanent complex formation between the catalyst complex and acrylonitrile, and a reaction scheme is proposed. 相似文献