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排序方式: 共有103条查询结果,搜索用时 109 毫秒
1.
The thermolysis of dicarbonylcyclopentadienyliron dimer in a sealed tube at 300°C has been reported to produce ferrocene, carbon monoxide, carbon dioxide, cyclopentadiene and elemental iron. We observe in addition to these products the production of biferrocene and elemental carbon. Thermolysis of carbonylcyclopentadienyliron tetramer (produced from the dimer by thermolysis in refluxing xylene) produces ferrocene, iron and carbon monoxidre; no biferrocene, carbon dioxide or elemental carbon are produced. A scheme is proposed to account for these products. 相似文献
2.
Previous work has shown that -disubstituted (acac)2 titanium (IV) complexes exist in solution as nonrigid molecules [1]. These studies were followed by variable temperature 1H NMR spectroscopy. The spectra shows that for the dialkoxy and dihalo complexes the acetylacetonate (acac) rings exchange the methyl groups between the two nonequivalent sites of the cis isomer. These rearrangements take place an intramolecular rearrangement: both twisting and one bond rupture mechanisms have been suggested for these stero-chemical rearrangements [2-4]. 相似文献
3.
Wilkie GD Elliott GI Blagg BS Wolkenberg SE Soenen DR Miller MM Pollack S Boger DL 《Journal of the American Chemical Society》2002,124(38):11292-11294
The scope of intramolecular Diels-Alder and a novel tandem Diels-Alder/1,3-dipolar cycloaddition cascade of 1,3,4-oxadiazoles is disclosed. In the cases examined, the tandem cycloadditions construct three new rings with formation of four new C-C bonds and set all six stereocenters about a central six-membered ring in a single step including three contiguous and four total quaternary centers without a trace of a second diastereomer. 相似文献
4.
Thitivat Suebsaeng Charles A. Wilkie Vern T. Burger Janet Carter Charles Eric Brown 《Journal of polymer science. Part A, Polymer chemistry》1984,22(4):945-957
The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13C-NMR, FR-IR, and MAS 31P-NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO2, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation. 相似文献
5.
Two methacrylate‐modified clays have been prepared and used to produce nanocomposites of polystyrene and poly(methyl methacrylate) by in situ polymerization. These nanocomposites have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cone calorimetry and the evaluation of mechanical properties. When the clay contains only a single methacrylate unit, the styrene system is exfoliated but methacrylate is intercalated. When two methacrylate units are present on the cation of the clay, both systems are exfoliated. TGA data show that the thermal stability of all the nanocomposites is improved, as expected. The relationships between the fire properties and nanostructure of the nanocomposites are complicated, as shown by cone calorimetry. The conclusions that one may reach using cone calorimetry do not completely agree with those from XRD and TEM. The evaluation of mechanical properties shows an increase in Young's modulus for all nanocomposites along with a decrease in elongation; tensile strength is decreased for methacrylate nanocomposites but increased for styrenics systems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
Donald R. Dimmel Charles A. Wilkie Paul J. Lamothe 《Journal of mass spectrometry : JMS》1975,10(1):18-25
The mass spectra of (Me3Sn)nCH4?n, where n varies from 1 to 4, (Me3Sn)2CClX, where X equals H, Cl, Br or I, together with some tetraalkyltin compounds and Me3SnCCl3, are presented. Comparisons with mass spectra of the silicon analogs1 show a large number of similarities, including the appearance of allylic ions which require Group IV metal to carbon π-bonding. Multiple rearrangements are observed with the halogenated tin compounds which bring the α-halogen into direct bonding with the tin atom. 相似文献
7.
Jianxian Xue Charles A. Wilkie 《Journal of polymer science. Part A, Polymer chemistry》1995,33(7):1019-1024
When a poly(ethylene terephthalate), PET, film is heated in an aqueous solution of methacrylic acid in the presence of hydrogen peroxide as an initiator, it is found that the weight of the film is increased. The amount of methacrylic acid that may be added onto the film is dependent upon the concentration of the monomer, the initiator, and the temperature at which the reaction occurs. Pretreatment of the film with 1,1,2,2,tetrachloroethane causes swelling and the amount of add-on is increased as the swelling level increases. Methacrylic-acid-modified PET films hydrolyze at room temperature in aqueous sodium hydroxide; the rate of hydrolysis is dependent upon the amount of add-on and the concentration of the base. This procedure leads to a chemically induced blend of polymethacrylic acid and poly(ethylene terephthalate), and grafting of the monomer onto the polymer film does not occur. © 1995 John Wiley & Sons, Inc. 相似文献
8.
Direct observations of infrared absorption in the weakly bound dimer of carbonyl sulphide, produced in pulsed molecular beams, have been made. Diode laser spectra in the 5 micron, carbonyl stretching, wavelength region were recorded with FWHM linewidths of approximately 100 MHz. All of the observations are consistent with OCS dimer having a C 2h , centrosymmetric geometry, with the centres of mass of the monomers nearly opposite one another. This essentially perpendicular structure places the S atoms close to the centre of the complex. The perpendicular distance between the monomer axes is 3·64 Å. Intermolecular potential functions containing dispersion and electrostatic contributions are discussed. 相似文献
9.
α‐zirconium phosphate (ZrP) (prepared by both reflux and hydrothermal methods) is silylated with chlorotrimethylsilane and characterized by X‐ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Polystyrene/silylated‐ZrP composites show higher thermal stability as the ZrP content increases. Cone calorimetry suggests that the reduction of the peak heat release rate of polystyrene (PS)/ZrP composites does not increase as the ZrP loading increases; the aspect ratio of ZrP has little effect in fire performance of PS/ZrP composites. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
Bekzat ABDIKADYR Alp KILI Onur ALEV Serkan BÜYÜKK
SE Zafer Ziya
ZTÜRK 《Turkish Journal of Chemistry》2021,45(2):295
Pristine and WO3 decorated TiO2 nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO2 NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO2 NRs and thermally oxidised to obtain WO3 nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO2 NRs with WO3. 相似文献