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WIREs Comput Mol Sci
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Microkinetic modeling in homogeneous catalysis

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Computational homogeneous catalysis has focused traditionally on the calculation of free energy barriers, which are ultimately related to rate constants. Experiments do not focus on rate constants, but on reaction rates, which depend also on concentrations. The increasing efficiency of DFT and other electronic structure techniques has led to the development of models that provide quite accurate rate constants, to the extent that improved agreement with experiment requires the introduction of the role of concentration. Microkinetic modeling, consisting in the construction of explicit kinetic reaction networks merging the rate constants provided by calculation and concentration data supplied by experiment, is a simple and elegant way to introduce concentration effects in the computational description of homogeneous catalysis. It has a long history of application in computational heterogeneous catalysis and experimental biochemistry, but its use in computational homogeneous catalysis is still in an early stage. There are a number of situations in homogeneous catalysis where microkinetics have been shown to be critical, such as systems with complex reaction networks and systems where one key species has a concentration orders of magnitude different from the others. Microkinetic modeling, with its low computational cost, is likely to become a standard tool in computational homogeneous catalysis. It is certainly not necessary for all theoretical studies, but the researcher should always be aware of its existence. This article is categorized under: Structure and Mechanism > Reaction Mechanisms and Catalysis
Example of catalytic cycle with corresponding chemical equations and associated free energies for each species. Energies in kcal/mol
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Evolution of the product ratio [prodA]/[prodB] over time (in logarithmic scale and in seconds) in the hypothetic catalytic cycle. Four different sets of initial concentrations are considered: [reactA]0 = [reactB]0 = 0.01 M (blue), 0.7 M (brown), 1.4 M (orange), and 2.0 M (yellow)
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Examples of a hypothetical catalytic cycle highlighting the importance of reactions orders
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Schematic representation of the mechanism for the halogen abstraction (top) and oxidative addition (bottom)
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Schematic representation of the mechanism for the photo‐initiated aromatic perfluoroalkylation of α‐cyano arylacetates
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Schematic representation of the simplified mechanism for the Pd‐catalyzed decarboxylative transformation of vinyl cyclic carbonates
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Top, legend of species representation. Right, reaction network of computed minima related to cucurbit[6]uril and its guests (some connections omitted). Left, pruned reaction network of structures selected for microkinetic model. Free energies in kcal/mol. Bottom left square, uncatalyzed reaction
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Schematic representation of the competition between alkane activation and diazocompound destruction (homocoupling) processes
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Differential equations derived from the example catalytic cycle depicted in Figure and initial concentrations. A graphic with the microkinetic model outcome with concentrations of the species involved in the example (mol/L) over time (time in logarithmic scale and in seconds) is also presented
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Structure and Mechanism > Reaction Mechanisms and Catalysis

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