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1.
Palladium 15-20 nm particles stabilized by a Keggin-type polyoxometalate were prepared by reduction of K(5)PPdW(11)O(39) with H(2). The nanoparticles were shown to be effective catalysts for Suzuki-, Heck-, and Stille-type carbon-carbon coupling and carbon-nitrogen coupling reactions of bromoarenes in aqueous media. Chloroarenes were also reactive in reaction media without solvent. [reaction: see text] 相似文献
2.
Summary The chlorobenzaldehydes, 2-bromo-4-tolualdehyde and 2-iodobenzaldehyde react with IrCl(CO)(PPh3)2 at 190 to 220° to give PhIrCl2(CO)(PPh3)2,p-tolyl IrBr2(CO)(PPh3)2 and PhIrCl2(CO)(PPh3), respectively. Iodo-and bromobenzene form PhIrCl(Hal)(CO)(PPh3)2 complexes, whereas chlorobenzene does not react under these conditions. Halogen transfer from the aromatic to the metal atom in the reaction of halobenzaldehydes, and halogen extrusion in various homogeneously catalyzed processes, are assumed to follow similar reaction patterns. 相似文献
3.
Kogan V Aizenshtat Z Neumann R 《Angewandte Chemie (International ed. in English)》1999,38(22):3331-3334
Excellent deoxygenation of ketones and aldehydes is achieved with Keggin-type polyoxometalates in the presence of hydrogen (see Equation (1) for an example). The mixed addenda phosphovanadomolybdate [PV(2)Mo(10)O(4)](5-) was found to be the best catalyst. X-ray diffraction and IR studies suggest that the polyoxometalates are structurally stable under the strongly reducing conditions. 相似文献
4.
5.
U Green Z Aizenshtat S Ruthstein H Cohen 《Physical chemistry chemical physics : PCCP》2012,14(37):13046-13052
Once coal is excavated it comes into contact with atmospheric oxygen and begins to undergo low temperature oxidation. The mechanism by which the molecular oxygen interacts with the coal macromolecule is suggested to occur in several steps. These steps primarily involve O(2) diffusion to the surface where physical adsorption followed by chemical adsorption takes place. The chemical adsorption forms several types of oxides that can subsequently react to form several products, primarily CO(2). It has also been suggested that some of these oxidation mechanisms might involve radical reactions. As the previous studies were conducted under conditions where significant structural changes occur it is possible that in the low temperature range (T < 100 °C) the oxidation mechanism is different. Several different rank (lignite-subbituminous-bituminous) coals were isothermally heated at 95 °C in an air atmosphere for a period of up to 6 months and samples were collected at two week intervals. The radical concentration of each sample was measured by Continuous Wave Electron Paramagnetic Resonance (CW-EPR). It is apparent that there are distinct differences between the lower rank (lignite) and the higher rank (subbituminous, bituminous) coals. The lower rank coals exhibited only carbon centered radicals with an adjacent oxygen atom and the higher rank coals exhibited only carbon centered radicals. Interestingly, the lower rank coals exhibited no change in radical concentration due to the long term oxidation treatment while the higher rank coals showed a distinct increase in the radical concentration. These findings shed new light on the complex heterogeneous low temperature oxidation reactions occurring at the coal surface. 相似文献
6.
Thermochemical sulfate reduction a review 总被引:2,自引:0,他引:2
The high concentrations of hydrogen sulfide found in many oil and gas fields is thought to arise from the oxidation of petroleum
hydrocarbons by sulfate—a reaction that reduces the value of the resource. This review, undertaken in order to better understand
the geochemistry of TSR reaction in oil field sediments, covers the relevant information on thermochemical sulfate reduction
(TSR) to 1991. The theoretical and experimental aspects of TSR reactions (including sulfur and carbon isotope studies) are
reviewed and their significance to the geochemical system discussed. The present review agrees with previous suggestions that
biochemical reduction of sulfate dominates in sedimentary environments below 120°C, and supports the possibility that reactive
sulfur species will oxidize certain organic molecules at meaningful rates in geochemically reasonable reaction periods at
temperatures above 175°C. We conclude that under typical petroleum reservoir reaction conditions, both elemental sulfur and
polysulfides are capable of oxidizing some organic molecules under basic conditions. But that sulfate alone will not react
unless lower oxidation state sulfur is present. The possible interaction of low-valence-state sulfur with sulfate to form
TSR active oxidants is examined. both H2S and SO
4
2−
are required for the formation of active polysufide reductants (e.g. thiosulfate or polythionates) in TSR systems. Such intermediates
can serve to lower the overall activation energy of the oxidation of hydrocarbons by sulfate via thermal generation of sulfur
radicals that can function as TSR active oxidants in many oil field sediments. We suggest that some proposed chemical mechanisms
for TSR need to be experimentally verified and the results re-interpreted with respect to TSR relations in geologic systems.
Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65th birthday 相似文献
7.
Moshe Weitzberg Zeev Aizenshtat Jochanan Blum 《Journal of heterocyclic chemistry》1984,21(6):1597-1601
Reactions of phenanthrene 9,10-imine (1) with alkyl halides, sodium azide and ammonium thiocyanate in two liquid phase systems were investigated. In the presence of aqueous sodium hydroxide and alkyl halides triethylbenzylammonium (TEBA) salts promote N-alkylation of 1 with preservation of the aziridine ring. Tetrabutylammonium (TBA) salts catalyze nucleophilic substitutions in which the three membered ring is cleaved. Aqueous sodium azide reacts with 1 to give trans-10-azido-9,10-dihydro-9-phenanthrenamine (2) . Ammonium and potassium thiocyanate cause expansion of the aziridine ring; while the unsubstituted imine 1 yields the 2-thiazolamine derivative 4 , N-butylphenanthrene 9,10-imine (8) froms trans-3a,11b-dihydro-3-butylphenanthro[9,10-d]thiazol-2-imine (9) with an exocyclic CN bond. The structure of 9 was established by X-ray crystal analysis. 相似文献
8.
Sarah Shtelzer Moshe Weitzberg Juliette Jeries Tuvia Sheradsky Zeev Aizenshtat Jochanan Blum 《Journal of heterocyclic chemistry》1984,21(1):1-3
Phenanthrene 9,10-imine ( 1 ) was shown to undergo N-alkylation without aziridine ring cleavage by (a) metallation with sodium methylsulfinylmethide followed by addition of an alkyl halide at −20° (b) reaction of 1 , sodium hydride and the halide in dimethylformamide at 40° (c) treatment of a dichloromethane solution of 1 , the halide and triethylbenzylammonium chloride with aqueous sodium hydroxide under phase transfer conditions. The syntheses of N-isopropyl-, N-butyl-, N-pentyl-, N-allyl- and N-benzylphenanthrene 9,10-imine ( 2–6 ) are described. 相似文献
9.
Moshe Weitzberg Zeev Aizenshtat Jochanan Blum 《Journal of heterocyclic chemistry》1981,18(8):1513-1516
Chlorides of carboxylic, sulfonic and phosphoric acids proved to convert phenanthrene-9,10-imine into the corresponding rearranged acet- sulfon- and phosphonamidophenanthrene. Trimethylchlorosilane and N,O-bis(trimethylsilyl)acetamide reacted with the imine without destruction of the aziridine ring. The silylated compound could be transferred into the respective N-substituted phenanthrene-9,10-imines when treated with acetyl-, methanesulfonyl-, 4-tosyl- and diethylphosphoryl chloride. A remarkably stable N-chlorophenanthrene-9,10-imine was obtained from the unsubstituted compound and N-chlorosuccinimide. 相似文献
10.
Methylation of polysulfides [(NH4)2Sn)] by reaction with CF3SO3CH3 followed by separation of the produced dimethylpolysulfides by liquid chromatography and subsequent highly accurate stable isotope analysis by a continuous-flow isotope ratio mass spectrometer shows that polysulfide anions in an aqueous solution exchange isotopes with the other sulfur species in the system. It demonstrates for the first time that polysulfide anions are 34S-enriched in equilibrium relative to total sulfur as a function of their sulfur chain length. 相似文献