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91.
一类Narcissistic反应过渡态的优化 总被引:1,自引:0,他引:1
我们对一类narcissistic 反应XCH_2-CH_2Y→[过渡态TS]→YCH_2—CH_2X (1)进行了研究,结果表明其过渡态能在对称性限制下由能量极小化方法较容易地给出. 采用IMSPAK分子轨道从头算程序,在IBM VM/370计算机系统上用STO—3G极小基组以平衡几何构型的能量梯度优化方法,在对称性限制下对反应(1)的几种反应体系的过渡态构型进行了优化,其结果列于表1. 相似文献
92.
采用固相反应合成了四羟基苯基卟啉与与Fe^2+,Co^2+金属离子的配合物,在室温下,将其与分子O2作用,提纯后得到两种固态氧合配合物.通过元素分析、红外光谱(IR)、核磁共振氢谱(^1HNMR)、电导、热分析(TG/DTA)、紫外光谱(UV)等测试手段确定了氧合配合物的组成为[Co·THPP·O2](NO3)2·2H2O、[Fe·THPP·O2]Cl2·2H2O],可知1mol配合物吸收了1molO2,采用失重法测定了氧合配合物中的配位氧,确定1mol金属配合物吸收1molO2形成超氧配合物. 相似文献
93.
Several Pd-catalyzed reactions were explored to further functionalize the bromo-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one scaffold (Aba). We report in this paper suitable reaction conditions for Suzuki, Buchwald-Hartwig, and Heck reactions. The substitution pattern of the starting aminobenzazepinone turned out to be crucial for the success of these transition metal-catalyzed reactions, which often required modifications of standard literature procedures. The Pd-catalyzed methods provide access to novel substitution patterns of the Aba scaffold. 相似文献
94.
Bahattin Gümgüm Nermin Biricik Feyyaz Durap Ismail Özdemir Nevin Gürbüz Wee Han Ang Paul J. Dyson 《应用有机金属化学》2007,21(8):711-715
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
95.
In this paper, we establish two general theorems for equivalence between the Meir–Keeler type contractive conditions and the contractive definitions involving gauge functions. One of these theorems is an extension of a recent result of Lim (On characterization of Meir–Keeler contractive maps, Nonlinear Anal. 46 (2001) 113–120). 相似文献
96.
We consider a Bolza optimal control problem with state constraints. It is well known that under some technical assumptions every strong local minimizer of this problem satisfies first order necessary optimality conditions in the form of a constrained maximum principle. In general, the maximum principle may be abnormal or even degenerate and so does not provide a sufficient information about optimal controls. In the recent literature some sufficient conditions were proposed to guarantee that at least one maximum principle is nondegenerate, cf. [A.V. Arutyanov, S.M. Aseev, Investigation of the degeneracy phenomenon of the maximum principle for optimal control problems with state constraints, SIAM J. Control Optim. 35 (1997) 930–952; F. Rampazzo, R.B. Vinter, A theorem on existence of neighbouring trajectories satisfying a state constraint, with applications to optimal control, IMA 16 (4) (1999) 335–351; F. Rampazzo, R.B. Vinter, Degenerate optimal control problems with state constraints, SIAM J. Control Optim. 39 (4) (2000) 989–1007]. Our aim is to show that actually conditions of a similar nature guarantee normality of every nondegenerate maximum principle. In particular we allow the initial condition to be fixed and the state constraints to be nonsmooth. To prove normality we use J. Yorke type linearization of control systems and show the existence of a solution to a linearized control system satisfying new state constraints defined, in turn, by linearization of the original set of constraints along an extremal trajectory. 相似文献
97.
98.
Necessary and sufficient conditions in constrained optimization 总被引:22,自引:0,他引:22
Additional conditions are attached to the Kuhn-Tucker conditions giving a set of conditions which are both necessary and sufficient
for optimality in constrained optimization, under appropriate constraint qualifications. Necessary and sufficient conditions
are also given for optimality of the dual problem. Duality and converse duality are treated accordingly. 相似文献
99.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of simpler linear differentialoperators and a nonlinear term. 相似文献
100.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(1):130-137
We have shown previously that iodosylbenzene–iron(III ) porphyrin intermediates ( 2 ) are generated in the reactions of oxoiron(IV ) porphyrin π‐cation radicals ( 1 ) and iodobenzene (PhI), that 1 and 2 are at equilibrium in the presence of PhI, and that the epoxidation of olefins by 2 affords high yields of epoxide products. In the present work, we report detailed mechanistic studies on the nature of the equilibrium between 1 and 2 in the presence of iodoarenes (ArI), the determination of reactive species responsible for olefin epoxidation when two intermediates (i.e., 1 and 2 ) are present in a reaction solution, and the fast oxygen exchange between 1 and H218O in the presence of ArI. In the first part, we have provided strong evidence that 1 and 2 are indeed at equilibrium and that the equilibrium is controlled by factors such as the electronic nature of iron porphyrins, the electron richness of ArI, and the concentration of ArI. Secondly, we have demonstrated that 1 is the sole active oxidant in olefin epoxidation when 1 and 2 are present concurrently in a reaction solution. Finally, we have shown that the presence of ArI in a reaction solution containing 1 and H218O facilitates the oxygen exchange between the oxo group of 1 and H218O and that the oxygen exchange is markedly influenced by factors such as ArI incubation time, the amounts of ArI and H218O used, and the electronic nature of ArI. The latter results are rationalized by the formation of an undetectable amount of 2 from the reaction of 1 and ArI through equilibrium that leads to a fast oxygen exchange between 2 and H218O. 相似文献