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941.
942.
本文用自旋捕捉-ESR技术研究了二茂戊铁、环二烯和胺甲基类取代二茂铁的紫外光解过程中的活泼自由基。结果表明,二茂铁光解初级过程中生成的自由基为(C_5H_5Fe)·和C_5H_5·,其衍生物光解则生成(C_5H_5Fe)·和RC_5H_4·,而(C_5H_5Fe)·还可以进一步分解给出C_5H_5和Fe。 相似文献
943.
R. Bruce King 《Theoretical chemistry accounts》1980,56(4):269-296
The following procedure is described for investigating the qualitative dynamics of simple chemical systems: 1) A so-called influence diagram is generated representing the relationships between the reference reactants (phase-determining intermediates); 2) This influence diagram is used to generate a truth table indicating possible transitions between state vectors representing the signs of the time derivatives of of the reference reactant concentrations; 3) The truth table is used to determine a state transition diagram representing the flow topology around unstable equilibrium points; 4) The characteristic equation of the adjacency matrix of the influence diagram is solved in order to determine the presence of such unstable equilibrium points. The two types of qualitative dynamics possible for chemical systems containing two reference reactants and one feedback circuit are bifurcation between two attracting regions (bistability) and limit cycle oscillation. However, in two reference reactant systems oscillation requires an additional self-activating loop to generate the unstable equilibrium point required for its realization. Bistability and limit cycle oscillation are also two of the possible types of qualitative dynamics for chemical systems containing three reference reactants. However, chemical systems with three reference reactants and two or more feedback circuits can also contain interlocking limit cycles, which can lead to toroidal oscillations or chaos. The influence diagrams are given for the systems exhibiting these various types of dynamic behavior along with a summary of the important properties of all 729 possible influences for simple chemical systems containing three reference reactants. 相似文献
945.
946.
Hans‐Peter Kormann Günter Schmid Katrin Pelzer K. Philippot Bruno Chaudret 《无机化学与普通化学杂志》2004,630(12):1913-1918
Nanoporous alumina membranes, loaded with palladium and ruthenium nanoparticles of various size, were used for gas phase hydrogenation of 1, 3‐butadiene and for oxidation of carbon monoxide, respectively. Those membranes contain 109 ‐ 1011 pores per cm2, all running perpendicular to the surface. Membrane discs of 20 mm in diameter and only 60 μm thick, incorporated in a reactor in which the reactants can be pumped in a closed circuit through the pores, turned out to very actively catalyze hydrogenation of butadiene (Pd) and oxidation of CO (Ru). The activity of the Pd catalysts depends characteristically on the particles size, the gas flow, and of the educts ratio. As could be expected, larger particles are less active than smaller ones, whereas increasing gas flows in case of hydrogenation accelerates the reactions. Excessive hydrogen reduces selectivity with respect to the various butenes, but favours formation of butane. 相似文献
947.
The rhodium-phosphine complex catalyst Rh(CO)(acac)(PPh3)(Ⅰ) for 1-hexene hydroformylation was studied under the following reaction conditions: CO/H2=1(mole rate), pressure 1.0 MPa, temperature 25-120℃, by using the pressurized in-situ 1H NMR technique. Experimental results indicated that the formation of a rhodium hydride complex from (Ⅰ) began at room temperature and its amount increased with increasing of reaction temperature. This intermediate complex began to decompose at 100℃ and disapeared completely at 120℃. The intensity change of the proton signal was parallel to catalytical activity in hydroformylation of olefins. Under pure CO pressure the proton signal of Ph-H bond was not observed. There was a 0.2 ppm difference in proton chemical shifts of Rh-H bond under pure H2 pressure and under H2+CO pressure. The results showed that the rhodium-hydride carbonyl complex is the active intermediate in the industrial hydroformylation process. 相似文献
948.
Sodium poly(styrenesulfonate)(polySSNa)-grafted polymer nanoparticles were synthesized by core-cross-linking of block copolymer micelles and subsequent chemical transformation. Block copolymers, poly(p-((1-methyl)silacyclobutyl)styrene-block-poly(neopentyl p-styrenesulfonate)s, polySBS-b-polySSPen, were synthesized by nitroxy-mediated living radical polymerization. The block copolymers formed micelles (Rh=15-23 nm, where Rh represents the hydrodynamic radius) with a polySBS core and polySSPen shell in acetone. The micelle core was cross-linked by ring-opening polymerization of silacyclobutyl groups in polySBS. Hydrolysis of the neopentyl groups provided polySSNa-grafted nanoparticles. The Rh of the particles before the hydrolysis ranged from 12 to 21 nm in acetone, while they varied to the range from 50 to 110 nm in water after the hydrolysis. 相似文献
949.
István Szilágyi Krisztina Imrik Dariusz Sarzisky Sándor Dóbé Tibor Bérces 《Reaction Kinetics and Catalysis Letters》2002,77(2):341-345
The title reactions have been studied at room temperature by applying the discharge flow method coupled with laser induced fluorescence detection of methoxy radicals and resonance fluorescence detection of bromine atoms. The following rate constants were determined: CH3O + Br Õ products (1) k
1 (298 K) = (3.4 ± 0.4 (1)) × 1013 cm3 mol-1 s-1, CH3O + Br2 Õ products (2) k
2 (298 K) £ 5 × 108 cm3 mol-1 s-1. 相似文献
950.
利用波长为266nm的激光光解CHBr3产生CH自由基,其与NO反应作为NCO自由基的来源.在298K,总压2660Pa的条件下,采用激光诱导荧光的方法,研究了NCO自由基与SO2、CS2的反应.得到了NCO自由基与SO2、CS2双分子反应速率常数分别为(1.8±0.3)×10-11和(3.1±0.4)×10-12cm3·molecule-1·s-1.对这两个反应在B3LYP/6-31 G(d)的水平上进行理论研究的结果表明,NCO自由基与SO2、CS2的反应是加成反应,其机理是NCO自由基中的N原子攻击反应物的中心原子,得到加成产物. 相似文献