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Transition state

About: Transition state is a research topic. Over the lifetime, 4978 publications have been published within this topic receiving 117965 citations. The topic is also known as: transition state of elementary reaction.


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Journal ArticleDOI
TL;DR: In this article, a combination of the DFT method with the computational description of environmental effects by solvent was applied to a theoretical study of the hydrogen transfer to imines by [2,3,4,5-Ph4(η5-C4COH)Ru(CO)2H] within a molecular model that closely mimics the authentic reaction conditions.

52 citations

Journal ArticleDOI
TL;DR: The observed selectivities in palladium-assisted allylic alkylation were correlated with the solvated transition-state structures obtained at high levels of theory for the reaction of cationic η3-allylpalladium complexes with different nucleophiles in the presence of a solvent as mentioned in this paper.
Abstract: The observed selectivities in palladium-assisted allylic alkylation were correlated with the solvated transition-state structures obtained at high levels of theory for the reaction of cationic η3-allylpalladium complexes with different nucleophiles in the presence of a solvent.

52 citations

Journal ArticleDOI
01 Jan 2009
TL;DR: The thermal cracking patterns from the decomposition and isomerization of octyl-1 radicals have been determined from the pyrolysis of n -octyl iodide in single pulse shock tube experiments at temperatures in the 850-1000 k range and pressures near 2 bar as discussed by the authors.
Abstract: The thermal cracking patterns from the decomposition and isomerization of octyl-1 radicals have been determined from the pyrolysis of n -octyl iodide in single pulse shock tube experiments at temperatures in the 850–1000 K range and pressures near 2 bar. Rate constants for the six beta bond scission and five of the six isomerization processes have been derived over all combustion conditions [0.1–100 bar, 700–1900 K]. Comparisons are made with previous studies on the decomposition of other primary radicals. Results are consistent with similar types of reactions having equal rate constants. The larger size of the octyl radicals makes contributions from secondary to secondary radical isomerization increasingly important. The results confirm that the 1–3 H-transfer process (involving a seven member cyclic transition state) have rate constants that are within a factor of 2 of those for the 1–4 process (six member cyclic transition state) It appears that rate constants for 1–2 H-transfer isomerization, involving an eight member cyclic transition state is unimportant in comparison to contributions from other isomerization processes. The strain energy does not appear to play an important role for these larger transition states. The implications of these results to larger fuel radicals will be discussed.

52 citations

Journal ArticleDOI
01 Oct 2019
TL;DR: In this paper, a modular approach for the systematic synthesis of polymer-nanocrystal hybrids, where palladium nanocrystals are encapsulated within tunable microporous polymer layers, is presented.
Abstract: Effective catalysts stabilize specific transition states and control the transport of species to and from catalytically active sites. Enzymes show these traits thanks to their diverse amino acid functional groups encapsulating metal centres, but are limited in the reaction conditions in which they can operate. Realizing a catalyst with this kinetic and transport control that can be used under demanding industrial conditions is challenging. Here, we show a modular approach for the systematic synthesis of polymer–nanocrystal hybrids, where palladium nanocrystals are encapsulated within tunable microporous polymer layers. The polymer chemistry and morphology control the catalytic performance of the metal sites, affecting the transition state for CO oxidation and controlling the transport of CO2 away from the active site. This approach can be applied to other polymer–nanocrystal compositions and catalytic applications, and is therefore expected to have an impact in many areas of catalysis. Encapsulation is an effective strategy to tune metal-catalysed reactions, although its potential has not been fully explored. Here, design principles and advanced understanding of the reactivity of different polymer-encapsulated Pd nanocrystals are provided using CO oxidation as a benchmark reaction.

52 citations

Journal ArticleDOI
TL;DR: In this paper, computational analysis of enzyme motions leading to transition state formation suggests that local catalytic site motions on the femtoseconds provide the mechanism to locate transition states.
Abstract: ConspectusEnzymatic transition states have lifetimes of a few femtoseconds (fs). Computational analysis of enzyme motions leading to transition state formation suggests that local catalytic site motions on the fs time scale provide the mechanism to locate transition states. An experimental test of protein fs motion and its relation to transition state formation can be provided by isotopically heavy proteins. Heavy enzymes have predictable mass-altered bond vibration states without altered electrostatic properties, according to the Born–Oppenheimer approximation. On-enzyme chemistry is slowed in most heavy proteins, consistent with altered protein bond frequencies slowing the search for the transition state. In other heavy enzymes, structural changes involved in reactant binding and release are also influenced. Slow protein motions associated with substrate binding and catalytic site preorganization are essential to allow the subsequent fs motions to locate the transition state and to facilitate the effici...

52 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202364
2022136
2021148
2020155
2019145
2018147