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排序方式: 共有106条查询结果,搜索用时 15 毫秒
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Carola Tortora Christina Mai Francesca Cascella Dr. Michael Mauksch Prof. Dr. Andreas Seidel-Morgenstern Prof. Dr. Heike Lorenz Prof. Dr. Svetlana B. Tsogoeva 《Chemphyschem》2020,21(16):1775-1787
Viedma deracemization is based on solution phase racemization, dissolution of racemic or scalemic conglomerates and crystal growth through autocatalytic cluster formation. With rate limiting racemization, its acceleration by appropriate catalysts may result in speeding up deracemization. A conglomerate-forming chiral compound may principally racemize directly, or via reverse of its formation reaction. For a hydrazine derivative, we investigated available racemization pathways in presence of pyrrolidine or thiourea amine as base catalysts: via Mannich or aza-Michael reaction steps and their reverse, or by enolization. Racemization by enolization was computationally found to dominate, both under water-free conditions and in presence of water, involving a multitude of different pathways. Faster racemization in presence of water resulted indeed in more rapid deracemization, when the base was pyrrolidine. Under water-free conditions, the role of water as enolization catalyst is assumed by chiral hydrazine itself – in autocatalytic racemization and in which both reactant and product are catalysts. 相似文献
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In this paper, we study a reaction–diffusion system for an isothermal chemical reaction scheme governed by a quadratic autocatalytic step A+B→2B and a decay step B→C, where A, B, and C are the reactant, the autocatalyst, and the inner product, respectively. Previous numerical studies and experimental evidences demonstrate that if the autocatalyst is introduced locally into this autocatalytic reaction system where the reactant A initially distributes uniformly in the whole space, then a pair of waves will be generated and will propagate outwards from the initial reaction zone. One crucial feature of this phenomenon is that for the strong decay case, the formation of waves is independent of the amount of the autocatalyst B introduced into the system. It is this phenomenon of KPP-type which we would like to address in this paper. To study the propagation of reactant and autocatalyst analytically, we first use the tail behavior of waves to construct a pair of generalized super-/sub-solutions for the approximate system of the autocatalytic reaction system. Note that the autocatalytic reaction system does not enjoy comparison principle. Together with a family of truncated problems, we can establish the existence of a family of traveling waves with the minimal speed. Second, we use this pair of generalized super-/sub-solutions to show that the propagation of waves is fully determined by the rate of decay of the initial data at infinity in the sense of Aronson–Weinberger formulation, which in turn confirms the aforementioned numerical and experimental results. 相似文献
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Exceedingly Facile PhX Activation (X=Cl,Br, I) with Ruthenium(II): Arresting Kinetics,Autocatalysis, and Mechanisms
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Dr. Fedor M. Miloserdov Dr. David McKay Dr. Bianca K. Muñoz Dr. Hamidreza Samouei Prof. Stuart A. Macgregor Prof. Vladimir V. Grushin 《Angewandte Chemie (International ed. in English)》2015,54(29):8466-8470
[(Ph3P)3Ru(L)(H)2] (where L=H2 ( 1 ) in the presence of styrene, Ph3P ( 3 ), and N2 ( 4 )) cleave the Ph? X bond (X=Cl, Br, I) at RT to give [(Ph3P)3RuH(X)] ( 2 ) and PhH. A combined experimental and DFT study points to [(Ph3P)3Ru(H)2] as the reactive species generated upon spontaneous loss of L from 3 and 4 . The reaction of 3 with excess PhI displays striking kinetics which initially appears zeroth order in Ru. However mechanistic studies reveal that this is due to autocatalysis comprising two factors: 1) complex 2 , originating from the initial PhI activation with 3 , is roughly as reactive toward PhI as 3 itself; and 2) the Ph? I bond cleavage with the just‐produced 2 gives rise to [(Ph3P)2RuI2], which quickly comproportionates with the still‐present 3 to recover 2 . Both the initial and onward activation reactions involve PPh3 dissociation, PhI coordination to Ru through I, rearrangement to a η2‐PhI intermediate, and Ph? I oxidative addition. 相似文献
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Dr. Anthonius H. J. Engwerda Josh Southworth Dr. Maria A. Lebedeva Dr. Robert J. H. Scanes Prof. Dr. Philipp Kukura Prof. Dr. Stephen P. Fletcher 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20541-20546
We report chemically fuelled out-of-equilibrium self-replicating vesicles based on surfactant formation. We studied the vesicles’ autocatalytic formation using UPLC to determine monomer concentration and interferometric scattering microscopy at the nanoparticle level. Unlike related reports of chemically fuelled self-replicating micelles, our vesicular system was too stable to surfactant degradation to be maintained out of equilibrium. The introduction of a catalyst, which introduces a second catalytic cycle into the metabolic network, was used to close the first cycle. This shows how coupled catalytic cycles can create a metabolic network that allows the creation and perseverance of fuel-driven, out-of-equilibrium self-replicating vesicles. 相似文献
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The characterization of chaotic spatiotemporal dynamics has been studied for a representative nonlinear autocatalytic reaction
mechanism coupled with diffusion. This has been carried out by an analysis of the Lyapunov spectrum in spatiallylocalised regions. The linear scaling relationships observed in the invariant measures as a function of thesub-system size have been utilized to assess the controllability, stability and synchronization properties of the chaotic dynamics.
The dynamical synchronization properties of this high-dimensional system has been analyzed using suitable Lyapunov functionals.
The possibility of controlling spatiotemporal chaos for relevant objectives using available noisy scalar time-series data
with simultaneous self-adaptation of the control parameter(s) has also been discussed. 相似文献