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Journal articles on the topic 'Mechanism of reaction'

Author: Grafiati

Published: 30 May 2022

Last updated: 31 May 2022

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1

Bucher-Nurminen, Kurt. "Reaction veins in marbles formed by a fracture-reaction-seal mechanism." European Journal of Mineralogy 1, no. 5 (November 16, 1989): 701–14. http://dx.doi.org/10.1127/ejm/1/5/0701.

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2

Ardèvol, Albert, Javier Iglesias-Fernández, Víctor Rojas-Cervellera, and Carme Rovira. "The reaction mechanism of retaining glycosyltransferases." Biochemical Society Transactions 44, no. 1 (February 9, 2016): 51–60. http://dx.doi.org/10.1042/bst20150177.

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The catalytic mechanism of retaining glycosyltransferases (ret-GTs) remains a controversial issue in glycobiology. By analogy to the well-established mechanism of retaining glycosidases, it was first suggested that ret-GTs follow a double-displacement mechanism. However, only family 6 GTs exhibit a putative nucleophile protein residue properly located in the active site to participate in catalysis, prompting some authors to suggest an unusual single-displacement mechanism [named as front-face or SNi (substitution nucleophilic internal)-like]. This mechanism has now received strong support, from both experiment and theory, for several GT families except family 6, for which a double-displacement reaction is predicted. In the last few years, we have uncovered the molecular mechanisms of several retaining GTs by means of quantum mechanics/molecular mechanics (QM/MM) metadynamics simulations, which we overview in the present work.

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3

Koča, Jaroslav, Milan Kratochvíl, and Vladimír Kvasnička. "Reaction mechanism graphs." Collection of Czechoslovak Chemical Communications 50, no. 7 (1985): 1433–49. http://dx.doi.org/10.1135/cccc19851433.

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The concept of reaction mechanism graphs has been introduced. These graphs describe the decomposition of an arbitrary organic reaction into its most elementary mechanistic steps representing heterolytic or homolytic dissociation and association processes, etc.. A clustering method of reaction mechanism graphs with the same number of elementary steps is specified. The suggested formalism was successfully used in our preliminary computer analysis of reaction mechanism.

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4

Schwarz, K., C. Samanta, M. Fujiwara, H. Rebel, R. De Leo, N. Matsuoka, H. Utsunomiya, et al. "Reaction mechanism of." European Physical Journal A 7, no. 3 (2000): 367. http://dx.doi.org/10.1007/s100500050404.

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5

García-García, P., K. Segovia-Bravo, A. López-López, M. Jaren-Galán, and A. Garrido. "Mechanism and Polyphenols Involved in the Browning Reaction of Olives." Czech Journal of Food Sciences 27, Special Issue 1 (June 24, 2009): S195—S196. http://dx.doi.org/10.17221/1099-cjfs.

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The purpose of this work was to disclose the mechanisms of the browning reaction produced on the surface of the fresh Manzanilla olive cultivar due to the bruises caused during hand or mechanical harvesting. The role played by the different phenols in the browning reaction and the implication of the enzymes present in the olive flesh have also been studied. The reaction was reproduced in model solutions where olive phenol extracts were put into contact with crude enzymatic olive extracts (active or denaturised) in a solution buffered at the same pH of the olive flesh (5.0) added or not with ascorbic acid to prevent oxidation. The proposed mechanism would consist of two steps. First, there is an enzymatic release of hydroxytyrosol, due to the action of the fruits’ β-glucosidases and esterases on oleuropein and hydroxytyrosol glucoside; additional hydroxytyrosol can also be produced (in a markedly lower proportion) by the chemical hydrolysis of oleuropein. In a second phase, hydroxytyrosol and verbascoside are oxidised by the fruits‘ polyphenoloxidase (mainly) and by a chemical reaction, which occurs to a limited extent due to the olive flesh pH 5.0. This hypothesis of the browning reaction mechanism is in agreement with the results in fresh fruits, because oleuropein is the compound that decreased in a higher proportion when the olives were bruised; and the sum of the concentrations of compounds that contain hydroxytyrosol in its molecule is mainly responsible for the decrease in total phenols in olives.

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6

Dayal, Akash, Manish Shrivastava, Rajiv Upadhyaya, and Lakhbir Singh Brar. "Numerical Combustion Evaluation of Select Detailed Chemistry Mechanisms for Their Impact on Compression Ignition Diesel Engine Performance Prediction." Advanced Science, Engineering and Medicine 12, no. 8 (August 1, 2020): 1072–76. http://dx.doi.org/10.1166/asem.2020.2670.

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The study focuses on the selection of detailed chemistry model for numerical combustion of compression ignition diesel engine. Three different established chemical reaction mechanisms of different chemistry resolution are considered to predict the macro performance characteristics. The numerical computation is performed on turbocharged 5.67L 130PS commercial vehicle diesel engine. The three chemical reactions mechanisms are used for engine performance prediction analysis viz. PSM Mechanism (having 121 species and 593 reactions), ERC Mech reaction mechanism model (having 61 species with 235 reactions) and Chalmers’ reaction mechanism model (having 42 species with 168 reactions) for analyses. The surrogate diesel fuel n-heptane is used in the combustion analysis. By making use of the three-chemistry model, conclusive results indicate significant differences in the computational runtime without much loss in the accuracy of the performance characteristics (expressed as the indicated mean effective pressure (IMEP)).

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7

Wang, Zhi-Xiang, Ming-Bao Huang., and Ruo-Zhuang Liu. "Theoretical study on the insertion reaction of CH(X2Π) with CH4." Canadian Journal of Chemistry 75, no. 7 (July 1, 1997): 996–1001. http://dx.doi.org/10.1139/v97-119.

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The CH + CH4 reaction has been studied by means of ab initio molecular orbital calculations incorporating electron correlation with Møller–Plesset perturbation theory up to second and fourth orders with the 6-31G(d,p) and 6-311++G(2d,p) basis sets. An energetically feasible insertion reaction path has been found in the potential energy surface that confirms the experimental proposal for the mechanism of the CH + CH4 reaction. The feature of the mechanism for the CH + CH4 insertion reaction is found to be different from the feature of the mechanisms for the CH + NH3, CH + H2O, and CH + HF insertion reactions, but somewhat similar to that for the CH2 + CH4 insertion reaction. Energetic results for the CH + CH4 reactions are in agreement with experiment. Keywords: CH radical, methane, reaction mechanism.

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8

IWATA, YORITAKA, NAOYUKI ITAGAKI, JOACHIM A. MARUHN, and TAKAHARU OTSUKA. "THE COMPETITIVE REACTION MECHANISM IN EXOTIC NUCLEAR REACTIONS." International Journal of Modern Physics E 17, no. 09 (October 2008): 1660–68. http://dx.doi.org/10.1142/s0218301308010672.

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Two principal reaction dynamics are introduced. One is the spin displacement, which is caused from the spin-dependence of the interaction, and the other is the isovector displacement, which is caused from the isospin-dependence of it. The competition of these two dynamics is a rather important factor as the target or projectile has more excess neutrons or protons. In this paper the competitive reaction mechanism is theoretically formulated, where the time-dependent mean field calculations are performed for justification.

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9

Hirata, M., K. Ochi, and T. Takaki. "Reaction Mechanism in the N -> N Reactions." Progress of Theoretical Physics 100, no. 3 (September 1, 1998): 681–86. http://dx.doi.org/10.1143/ptp.100.681.

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10

Li, Yun, Hua-You Hu, Jian-Ping Ye, Hoong-Kun Fun, Hong-Wen Hu, and Jian-Hua Xu. "Reaction Modes and Mechanism in Indolizine Photooxygenation Reactions." Journal of Organic Chemistry 69, no. 7 (April 2004): 2332–39. http://dx.doi.org/10.1021/jo035070d.

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11

Croce, A. E. "First-order parallel and consecutive reaction mechanisms — Isosbestic points criterium." Canadian Journal of Chemistry 86, no. 9 (September 1, 2008): 918–24. http://dx.doi.org/10.1139/v08-098.

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A criterium for the selection of reaction mechanism derived from a condition for isosbestic points occurrence is presented. Analytical relationships involving the molar absorption coefficients of the species, which participate in a mechanism of parallel first-order reactions and the corresponding rate coefficients, are also reported. A model system of four species that present overlapping absorption spectra may correspond to the reactant and products of a system of parallel or consecutive first-order reactions. In the first case, under experimental conditions in which the absorbances are additive, the presence of an isosbestic point in the spectrum of the reaction mixture at a given wavelength leads to a time-independent ratio of the degree of advancement of reaction variables. From this, relevant kinetic information may be extracted, namely, the ratio of the reaction rate coefficients. Moreover, the occurrence of isosbestic points allows discarding the second mechanism. This conclusion is independent of the number of absorbing species. Model calculated examples show the application of the equations here derived. The resolution for the general case of mechanisms of N first-order reactions is provided.Key words: chemical kinetics, time-resolved absorption spectra, reaction mechanism.

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12

Stack, Andrew G., and Paul R. C. Kent. "Geochemical reaction mechanism discovery from molecular simulation." Environmental Chemistry 12, no. 1 (2015): 20. http://dx.doi.org/10.1071/en14045.

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Environmental context Computational simulations are providing an increasingly useful way to isolate specific geochemical and environmental reactions and to test how important they are to the overall rate. In this review, we summarise a few ways that one can simulate a reaction and discuss each technique’s overall strengths and weaknesses. Selected case studies illustrate how these techniques have helped to improve our understanding for geochemical and environmental problems. Abstract Methods to explore reactions using computer simulation are becoming increasingly quantitative, versatile and robust. In this review, a rationale for how molecular simulation can help build better geochemical kinetics models is first given. Some common methods are summarised that geochemists use to simulate reaction mechanisms, specifically classical molecular dynamics and quantum chemical methods and their strengths and weaknesses are also discussed. Useful tools such as umbrella sampling and metadynamics that enable one to explore reactions are discussed. Several case studies wherein geochemists have used these tools to understand reaction mechanisms are presented, including water exchange and sorption on aqueous species and mineral surfaces, surface charging, crystal growth and dissolution, and electron transfer. The effect that molecular simulation has had on our understanding of geochemical reactivity is highlighted in each case. In the future, it is anticipated that molecular simulation of geochemical reaction mechanisms will become more commonplace as a tool to validate and interpret experimental data, and provide a check on the plausibility of geochemical kinetic models.

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13

BOWDEN, K. "ChemInform Abstract: Reaction Constants and Reaction Mechanism." ChemInform 27, no. 20 (August 5, 2010): no. http://dx.doi.org/10.1002/chin.199620273.

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14

Rakovsky, Slavcho, Metody Anachkov, Mikhail Belitskii, and Gennady Zaikov. "Kinetics and Mechanism of the Ozone Reaction with Alcohols, Ketones, Ethers and Hydroxybenzenes." Chemistry & Chemical Technology 10, no. 4s (December 25, 2016): 531–51. http://dx.doi.org/10.23939/chcht10.04si.531.

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The review, based on 92 references, is focused on degradation of organics by ozonation and it comprises various classes of oxygen-containing organic compounds – alcohols, ketones, ethers and hydroxybenzenes. The mechanisms of a multitude of ozone reactions with these compounds in organic solvents are discussed in details, presenting the respective reaction schemes. The corresponding kinetic parameters are given and some thermodynamic parameters are also listed. The dependences of the kinetics and the mechanism of the ozonation reactions on the structure of the compounds, on the medium and on the reaction conditions are revealed. Various possible applications of ozonolysis are specified and discussed. All these reactions have practical importance for the protection of the environment.

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15

van der Donk, Wilfred A., Ah-Lim Tsai, and Richard J. Kulmacz. "The Cyclooxygenase Reaction Mechanism." Biochemistry 41, no. 52 (December 2002): 15451–58. http://dx.doi.org/10.1021/bi026938h.

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16

Yoshikawa, Shinya, and Atsuhiro Shimada. "Reaction Mechanism of CytochromecOxidase." Chemical Reviews 115, no. 4 (January 20, 2015): 1936–89. http://dx.doi.org/10.1021/cr500266a.

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17

Baran, V., M. Colonna, and M. Di Toro. "Neck fragmentation reaction mechanism." Nuclear Physics A 730, no. 3-4 (January 2004): 329–54. http://dx.doi.org/10.1016/j.nuclphysa.2003.10.022.

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18

Sun, Yang-Kook, and Chong S. Yoon. "The reaction mechanism revealed." Nature Nanotechnology 12, no. 6 (March 27, 2017): 503–4. http://dx.doi.org/10.1038/nnano.2017.40.

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19

Lv, Linhui, Yanlin Ye, Zhongxin Cao, Jun Xiao, Dongxing Jiang, Tao Zheng, hui Hua, et al. "Knockout Reaction Mechanism for6He+." Plasma Science and Technology 14, no. 6 (June 2012): 506–9. http://dx.doi.org/10.1088/1009-0630/14/6/15.

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20

Nhan, N. T. T., P. H. Kien, P. K. Hung, N. V. Hong, and L. T. San. "About the diffusion mechanism in the silica liquid." International Journal of Modern Physics B 30, no. 10 (April 20, 2016): 1650059. http://dx.doi.org/10.1142/s0217979216500594.

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In this paper, we have numerically studied the diffusion mechanism in silica liquid based on the idea that the collective movement of particles is controlled by reactions [Formula: see text] and [Formula: see text]. Four models at temperatures from 2600 K to 3500 K have been constructed by molecular dynamic simulation. The simulation shows that the liquid has a small amount of defect-cells which are of importance for the diffusion. In particular, the majority of reactions happen via defect-cells SiO5 and OSi3. Moreover, the defect-cells do not uniformly distribute in the liquid, but they have a tendency to locate nearby forming large cluster. Further, it is revealed that the spatial distribution of reactions is heterogeneous. We found two distinct clusters. First cluster (none-reaction cluster) consists of particles on which no reaction happens. The second cluster (reaction cluster) includes particles where the reactions happen. The size of clusters found is dependent with temperature and diffusion time. Moreover, the mobility of particles in none-reaction cluster is significantly smaller than in reaction cluster. This indicates the dynamics heterogeneity in the liquid. We suggest that the dynamics slowdown is originated from the percolation of none-reaction cluster.

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21

Long, Fengqin, Zheng Chen, Keli Han, Lu Zhang, and Wei Zhuang. "Differentiation between Enamines and Tautomerizable Imines Oxidation Reaction Mechanism using Electron-Vibration-Vibration Two Dimensional Infrared Spectroscopy." Molecules 24, no. 5 (March 1, 2019): 869. http://dx.doi.org/10.3390/molecules24050869.

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Intermediates lie at the center of chemical reaction mechanisms. However, detecting intermediates in an organic reaction and understanding its role in reaction mechanisms remains a big challenge. In this paper, we used the theoretical calculations to explore the potential of the electron-vibration-vibration two-dimensional infrared (EVV-2DIR) spectroscopy in detecting the intermediates in the oxidation reactions of enamines and tautomerizable imines with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). We show that while it is difficult to identify the intermediates from their infrared and Raman signals, the simulated EVV-2DIR spectra of these intermediates have well resolved spectral features, which are absent in the signals of reactants and products. These characteristic spectral signatures can, therefore, be used to reveal the reaction mechanism as well as monitor the reaction progress. Our work suggests the potential strength of EVV-2DIR technique in studying the molecular mechanism of organic reactions in general.

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22

Zhukov, Victor P., and Alan F. Kong. "A Compact Reaction Mechanism of Methane Oxidation at High Pressures." Progress in Reaction Kinetics and Mechanism 43, no. 1 (March 2018): 62–78. http://dx.doi.org/10.3184/146867818x15066862094914.

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A skeletal methane kinetic mechanism is developed for conditions relating to the combustion of undiluted methane–oxygen mixtures at high pressures. The new skeletal mechanism is based on the detailed mechanism of oxidation of alkanes by Zhukov (2009). The skeletal model has been created by eliminating unimportant species and reactions from the detailed mechanism. The reduction technique is based on the reaction path and sensitivity analyses. They allow one to determine the reactions and species that play important roles in combustion in rocket combustion chambers. The skeletal mechanism consists of 23 species and 51 reactions. The final and intermediate versions of the skeletal mechanism are compared with the parent detailed mechanism, with other reduced kinetic models and with experimental data on the ignition of methane at high pressures. This comparison shows that the developed skeletal mechanism has a better performance than other kinetic mechanisms in terms of accuracy and required computational power.

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23

Cao, Le, Chenggang Wang, Mao Mao, Holger Grosshans, and Nianwen Cao. "Derivation of the reduced reaction mechanisms of ozone depletion events in the Arctic spring by using concentration sensitivity analysis and principal component analysis." Atmospheric Chemistry and Physics 16, no. 23 (December 1, 2016): 14853–73. http://dx.doi.org/10.5194/acp-16-14853-2016.

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Abstract. The ozone depletion events (ODEs) in the springtime Arctic have been investigated since the 1980s. It is found that the depletion of ozone is highly associated with an auto-catalytic reaction cycle, which involves mostly the bromine-containing compounds. Moreover, bromide stored in various substrates in the Arctic such as the underlying surface covered by ice and snow can be also activated by the absorbed HOBr. Subsequently, this leads to an explosive increase of the bromine amount in the troposphere, which is called the “bromine explosion mechanism”. In the present study, a reaction scheme representing the chemistry of ozone depletion and halogen release is processed with two different mechanism reduction approaches, namely, the concentration sensitivity analysis and the principal component analysis. In the concentration sensitivity analysis, the interdependence of the mixing ratios of ozone and principal bromine species on the rate of each reaction in the ODE mechanism is identified. Furthermore, the most influential reactions in different time periods of ODEs are also revealed. By removing 11 reactions with the maximum absolute values of sensitivities lower than 10 %, a reduced reaction mechanism of ODEs is derived. The onsets of each time period of ODEs in simulations using the original reaction mechanism and the reduced reaction mechanism are identical while the maximum deviation of the mixing ratio of principal bromine species between different mechanisms is found to be less than 1 %. By performing the principal component analysis on an array of the sensitivity matrices, the dependence of a particular species concentration on a combination of the reaction rates in the mechanism is revealed. Redundant reactions are indicated by principal components corresponding to small eigenvalues and insignificant elements in principal components with large eigenvalues. Through this investigation, aside from the 11 reactions identified as unimportant in the concentration sensitivity analysis, additionally nine reactions were indicated to contribute only little to the total response of the system. Thus, they can be eliminated from the original reaction scheme. The results computed by applying the reduced reaction mechanism derived after the principal component analysis agree well with those by using the original reaction scheme. The maximum deviation of the mixing ratio of principal bromine species is found to be less than 10 %, which is guaranteed by the selection criterion adopted in the simplification process. Moreover, it is shown in the principal component analysis that O(1D) in the mechanism of ODEs is in quasi-steady state, which enables a following simplification of the reduced reaction mechanism obtained in the present study.

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24

Gao, Connie W., Joshua W. Allen, William H. Green, and Richard H. West. "Reaction Mechanism Generator: Automatic construction of chemical kinetic mechanisms." Computer Physics Communications 203 (June 2016): 212–25. http://dx.doi.org/10.1016/j.cpc.2016.02.013.

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25

Fuller, Jon, Alessandro Fortunelli, William A. Goddard III, and Qi An. "Reaction mechanism and kinetics for ammonia synthesis on the Fe(211) reconstructed surface." Physical Chemistry Chemical Physics 21, no. 21 (2019): 11444–54. http://dx.doi.org/10.1039/c9cp01611b.

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To provide guidelines to accelerate the Haber–Bosch (HB) process for synthesis of ammonia from hydrogen and nitrogen, we used Quantum Mechanics (QM) to determine the reaction mechanism and free energy reaction barriers under experimental reaction conditions (400 °C and 20 atm) for all 10 important surface reactions on the Fe(211)R surface.

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26

Le Corre, Stéphanie S., Mathieu Berchel, Hélène Couthon-Gourvès, Jean-Pierre Haelters, and Paul-Alain Jaffrès. "Atherton–Todd reaction: mechanism, scope and applications." Beilstein Journal of Organic Chemistry 10 (May 21, 2014): 1166–96. http://dx.doi.org/10.3762/bjoc.10.117.

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Initially, the Atherton–Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different nucleophiles. The mechanism of this reaction led to controversial reports over the past years and is adequately discussed. We also present the scope of the AT reaction. Finally, we investigate the AT reaction by means of exemplary applications, which mainly concern three topics. First, we discuss the activation of a phenol group as a phosphate which allows for subsequent transformations such as cross coupling and reduction. Next, we examine the AT reaction applied to produce fire retardant compounds. In the last section, we investigate the use of the AT reaction for the production of compounds employed for biological applications. The selected examples to illustrate the applications of the Atherton–Todd reaction mainly cover the past 15 years.

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27

Acosta-Guzmán, Paola, Alejandra Mateus-Gómez, and Diego Gamba-Sánchez. "Direct Transamidation Reactions: Mechanism and Recent Advances." Molecules 23, no. 9 (September 18, 2018): 2382. http://dx.doi.org/10.3390/molecules23092382.

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Amides are undeniably some of the most important compounds in Nature and the chemical industry, being present in biomolecules, materials, pharmaceuticals and many other substances. Unfortunately, the traditional synthesis of amides suffers from some important drawbacks, principally the use of stoichiometric activators or the need to use highly reactive carboxylic acid derivatives. In recent years, the transamidation reaction has emerged as a valuable alternative to prepare amides. The reactivity of amides makes their direct reaction with nitrogen nucleophiles difficult; thus, the direct transamidation reaction needs a catalyst in order to activate the amide moiety and to promote the completion of the reaction because equilibrium is established. In this review, we present research on direct transamidation reactions ranging from studies of the mechanism to the recent developments of more applicable and versatile methodologies, emphasizing those reactions involving activation with metal catalysts.

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28

Yang, Y. F., H. Y. Wang, J. G. Wang, R. Y. Zhao, and Q. C. Jiang. "Ignition and reaction mechanisms of thermal explosion reaction in the Ni-Ti-C system under air and Ar." Journal of Materials Research 24, no. 10 (October 2009): 3197–205. http://dx.doi.org/10.1557/jmr.2009.0370.

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The ignition and reaction mechanisms of the thermal explosion reaction in the Ni-Ti-C system under air and Ar conditions were investigated. The reaction for the formation of TiC can be initiated at a low temperature under air. The ignition temperature under air is much lower than that under Ar. Under Ar, both the ignition and reaction mechanisms consist of dissolution, reaction, and precipitation. Under air, the ignition mechanism is confirmed to be the chemical oven mechanism, and the reaction mechanism is dissolution, reaction, and precipitation. The mechanism of gas transport plays a much more minor role in the ignition and reaction processes under air.

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29

Aliyev, A. M., M. Y. Abbasov, M. G. Aliyeva, G. A. Alizade, and R. Yu Agayeva. "THE KINETICS AND MECHANISM OF THE SELECTIVE OXIDATIVE DEHYDROGENATION REACTİON OF METHYLCYCLOPENTANE." Azerbaijan Chemical Journal, no. 3 (September 28, 2021): 12–20. http://dx.doi.org/10.32737/0005-2531-2021-3-12-20.

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The oxidative dehydrogenation of alicyclic diene hydrocarbons refers to scarcely studied heterogeneous catalytic reactions which proceed with the participation of oxygen. The dehydrogenation of methylcyclopentane is an endothermic reaction. To improve the reaction kinetics, this research was to develop a structured catalyst by conductive metals (Cu, Zn, Co, Cr) support which could hold an adherent catalytic layer. The active phase was impregnated onto these support metals and the developed catalyst was tested for the dehydrogenation of methylcyclopentane. The catalyst preparation involved three main key steps which were support oxidative reaction, loading of active particles on the catalyst surface, preparation of an active catalyst layer on the surface finally bringing the catalyst into the active phase. Different types of catalyst activation and deactivation mechanisms stability have been studied in this investigation. The advantage of this works, the oxidative dehydrogenation of methylcyclopentane is that it occurs at the expense of oxygen in the air. The zeolite structure study helped identify the effect of the combination of catalysts, and adsorption of metals on clinoptilolite and dispersion on the selectivity of the catalyst particles. Numerical values of the kinetic parameters were calculated

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30

Mora, José, Cristian Cervantes, and Edgar Marquez. "New Insight into the Chloroacetanilide Herbicide Degradation Mechanism through a Nucleophilic Attack of Hydrogen Sulfide." International Journal of Molecular Sciences 19, no. 10 (September 21, 2018): 2864. http://dx.doi.org/10.3390/ijms19102864.

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The nucleophilic attack of hydrogen sulfide (HS−) on six different chloroacetanilide herbicides was evaluated theoretically using the dispersion-corrected hybrid functional wB97XD and the 6-311++G(2d,2p) Pople basis sets. The six evaluated substrates were propachlor (A), alachlor (B), metolachlor (C), tioacetanilide (D), β-anilide (E), and methylene (F). Three possible mechanisms were considered: (a) bimolecular nucleophilic substitution (SN2) reaction mechanism, (b) oxygen assistance, and (c) nitrogen assistance. Mechanisms based on O- and N-assistance were discarded due to a very high activation barrier in comparison with the corresponding SN2 mechanism, with the exception of compound F. The N-assistance mechanism for compound F had a free activation energy of 23.52 kcal/mol, which was close to the value for the corresponding SN2 mechanism (23.94 kcal/mol), as these two mechanisms could occur in parallel reactions with almost 50% of each one. In compounds A to D, an important electron-withdrawing effect of the C=O and C=S groups was seen, and consequently, the activation free energies in these SN2 reactions were smaller, with a value of approximately 18 kcal/mol. Instead, compounds E and F, which have a CH2 group in the β-position, presented a higher activation free energy (≈22 kcal/mol). Good agreement was found between experimental and theoretical values for all cases, and a reaction force analysis was performed on the intrinsic reaction coordinate profile in order to gain more details about the reaction mechanism. Finally, from the natural bond orbital (NBO) analysis, it was possible to evaluate the electronic reorganization through the reaction pathway where all the transition states were early in nature in the reaction coordinate (δBav < 50%); the transition states corresponding to compounds A to D turned out to be more synchronous than those for compounds E and F.

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31

Zettervall, Niklas, Christer Fureby, and Elna J. K. Nilsson. "Reduced Chemical Kinetic Reaction Mechanism for Dimethyl Ether-Air Combustion." Fuels 2, no. 3 (August 25, 2021): 323–44. http://dx.doi.org/10.3390/fuels2030019.

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Development and validation of a new reduced dimethyl ether-air (DME) reaction mechanism is presented. The mechanism was developed using a modular approach that has previously been applied to several alkane and alkene fuels, and the present work pioneers the use of the modular methodology, with its underlying H/C1/O base mechanism, on an oxygenated fuel. The development methodology uses a well-characterized H/C1/O base mechanism coupled to a reduced set of fuel and intermediate product submechanisms. The mechanism for DME presented in this work includes 30 species and 69 irreversible reactions. When used in combustion simulation the mechanism accurately reproduced key combustion characteristics and the small size enables use in computationally demanding Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS). It has been developed to accurately predict, among other parameters, laminar burning velocity and ignition delay times, including the negative temperature regime. The evaluation of the mechanism and comparison to experimental data and several detailed and reduced mechanisms covers a wide range of conditions with respect to temperature, pressure and fuel-to-air ratio. There is good agreement with experimental data and the detailed reference mechanisms at all investigated conditions. The mechanism uses fewer reactions than any previously presented DME-air mechanism, without losing in predictability.

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32

Taylor, Annette F. "Mechanism and Phenomenology of an Oscillating Chemical Reaction." Progress in Reaction Kinetics and Mechanism 27, no. 4 (December 2002): 247–326. http://dx.doi.org/10.3184/007967402103165414.

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Chemical reactions, which are far from equilibrium, are capable of displaying oscillations in species concentrations and hence in colour, electrode potential, pH and/or temperature. The oscillations arise from the interplay between positive and negative kinetic feedback. Mechanisms for such reactions are presented, along with the rich phenomenology that these systems exhibit, from complex oscillations and chemical waves, to stationary concentration patterns. This review will focus on the Belousov-Zhabotinksy reaction but reference to other reactions will be made where appropriate.

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33

Maruyama, Kazuhiro, and Toshimasa Katagiri. "Mechanism of the Grignard reaction. Reaction of benzil." Journal of the American Chemical Society 108, no. 20 (October 1986): 6263–70. http://dx.doi.org/10.1021/ja00280a025.

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34

Butuk, N., and J. P. Pemba. "Computing CHEMKIN Sensitivities Using Complex Variables." Journal of Engineering for Gas Turbines and Power 125, no. 3 (July 1, 2003): 854–58. http://dx.doi.org/10.1115/1.1469006.

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This paper discusses an accurate numerical approach based on complex variables for the computation of the Jacobian matrix of complex chemical reaction mechanisms. The Jacobian matrix is required in the calculation of low dimensional manifolds during kinetic chemical mechanism reduction. The approach is suitable for numerical computations of large-scale problems and is more accurate than the finite difference approach of computing Jacobians. The method is demonstrated via a nonlinear reaction mechanism for the synthesis of Bromide acid and a H2/Air mechanism using a modified CHEMKIN package. The Bromide mechanism consisted of five species participating in six elementary chemical reactions and the H2/Air mechanism consisted of 11 species and 23 reactions. In both cases it is shown that the method is superior to the finite difference approach of computing derivatives with an arbitrary computational step size h.

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35

Branca, Carmen, and Blasi di. "Parallel and series-reaction mechanisms of wood and char combustion." Thermal Science 8, no. 2 (2004): 51–64. http://dx.doi.org/10.2298/tsci0402051b.

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Thermo gravimetric curves in air of beech wood and char, obtained from conventional pyrolysis of beech wood at a laboratory scale, have been re-examined using different kinetic models. Multi-step reaction mechanisms consisting of either four (wood) or two (char) reactions are needed for accurate predictions of weight loss curves. In the case of wood, three reactions are linear in the reactant mass fraction whereas the fourth step presents a power-law dependence. A linear reaction for devolatilization and a non-linear reaction for combustion are used for the weight loss curves of char. It has been found that activation energies and pre-exponential factors are in variant with series or parallel reactions, providing changes in the stoichiometric coefficients. Further more, the activation energies of the two reactions occurring at higher temperatures in the four-step mechanism (wood) and those of the two-step mechanism (char) are the same. Thus pre-exponential factors and reaction order take into account variations in the char reactivity derived from different pyrolysis conditions.

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36

Kayser, Margaret M., Krista L. Hatt, and Donald L. Hooper. "Mechanism of Wittig reaction with cyclic anhydrides." Canadian Journal of Chemistry 70, no. 7 (July 1, 1992): 1985–96. http://dx.doi.org/10.1139/v92-249.

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The reactions of stabilized phosphoranes with cyclic anhydrides give enol-lactones as final products. The initial condensation, however, leads to the formation of acyclic adducts that are observable by NMR, can be easily trapped, and, in some cases, can be isolated. A study of the mechanism of these condensations by NMR spectroscopic methods and by various trapping experiments is described and the reaction pathway is proposed.

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37

Guosheng Wang, Guosheng Wang, and Siyu Han and Ronghui Xu Siyu Han and Ronghui Xu. "The Ring Formation Mechanism in Cyclization of Berberine." Journal of the chemical society of pakistan 43, no. 3 (2021): 308. http://dx.doi.org/10.52568/000578/jcsp/43.03.2021.

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Berberine hydrochloride is a natural alkaloid with significant antitumor activities against many types of cancer cells, can be synthesized by cyclic reaction with hydrochloride condensate and glyoxal as raw materials and copper chloride as catalyst. In this study, the transition and energy change for the each reaction step was calculated by the density functional theory program Dmol3 in Materials Studio 2017. and the results testified that there are two ring formation in the cycliztion process, and according to the result we proposed the mechanism of this cyclization reaction. We also use infrared and ultraviolet spectroscopy to monitor the reaction process in real time and prove the ring formation process. The reaction mechanism was firstly proposed at the basic results of above.

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38

Guosheng Wang, Guosheng Wang, and Siyu Han and Ronghui Xu Siyu Han and Ronghui Xu. "The Ring Formation Mechanism in Cyclization of Berberine." Journal of the chemical society of pakistan 43, no. 3 (2021): 308. http://dx.doi.org/10.52568/000578.

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Abstract:

Berberine hydrochloride is a natural alkaloid with significant antitumor activities against many types of cancer cells, can be synthesized by cyclic reaction with hydrochloride condensate and glyoxal as raw materials and copper chloride as catalyst. In this study, the transition and energy change for the each reaction step was calculated by the density functional theory program Dmol3 in Materials Studio 2017. and the results testified that there are two ring formation in the cycliztion process, and according to the result we proposed the mechanism of this cyclization reaction. We also use infrared and ultraviolet spectroscopy to monitor the reaction process in real time and prove the ring formation process. The reaction mechanism was firstly proposed at the basic results of above.

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39

Pastore, Christopher, and Moishe Garfinkle. "The expected time to attain chemical equilibrium from a thermodynamic probabilistic analysis." Canadian Journal of Chemistry 90, no. 3 (March 2012): 243–55. http://dx.doi.org/10.1139/v11-154.

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Employing a stochastic model, both Planck and Fokker proposed almost a century ago that stoichiometric chemical reactions proceed by a chain mechanism involving discrete reaction steps. To determine whether such a chain mechanism was in fact a valid mechanism for chemical reactions was the subject of a recent study (Garfinkle, M. 2002. J. Phys. Chem. 106A: 490). Using a thermodynamic–probabilistic algorithm the stochastic reaction paths were found to be in excellent agreement with the observed reaction paths plotted from experimental data. This study was then extended to test the conclusions of Ehrenfest and Prigogine that a chain mechanism dictates that the number of discrete reaction steps required for a chemical reaction to attain equilibrium must be finite. The stochastic and empirical reaction paths were compared using experimental data for first-, second-, and third-order reactions as well as fractional order reactions. The empirical verification was excellent.

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40

Kochetova, Ludmila B., and Tatiana P. Kustova. "Kinetics and mechanism of acyl transfer reactions. Part 15. Quantumchemicalsimulation of mechanisms of reactions of N-ethylaniline sulfonation." Butlerov Communications 57, no. 2 (February 28, 2019): 19–27. http://dx.doi.org/10.37952/roi-jbc-01/19-57-2-19.

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The RHF/6-31G(d) quantum chemical simulation of the mechanism of the interaction of the secondary fatty aromatic amine N-ethylaniline with benzenesulfonyl chloride under conditions of non-specific water solvation, using the continuum model of the solvent, as well as of sulfonylation reactions of N-ethylaniline solvation complexes containing one water molecule, modeled specific solvation of N-ethylaniline with water, and one molecule of water and one of dioxane, which simulate the solvation of the amine with aqueous dioxane. Three-dimensional potential energy surface of these processes is calculated. It is shown that in the case of a reaction proceeding under conditions of non-specific solvation of reagents, the route with axial attack of the N-ethylaniline molecule to the sulfonyl reaction center is realized, in the two other cases the reactions proceed along a single route, starting as an axial attack of the nucleophile, which goes further with decreasing of the attack angle as reagent molecules approach each other. It was established that all the simulated reactions proceed in accordance with bimolecular coordinated mechanism of nucleophilic substitution SN2, which implies the formation of a single transition state in the reaction path. It was found that geometrical configuration of the reaction center in the transition state of N-ethylaniline reaction with benzenesulfonyl chloride under non-specific solvation by water is close to trigonal-bipyramidal, which is determined by the axial direction of the nucleophilic attack, in the two other cases it is medium between the trigonal-bipyramidal and tetragonal-pyramidal, which is associated with the change in the angle of N-ethylaniline attack as the reactant molecules approach each other. In a reaction involving N-ethylaniline monohydrate, a water molecule forms a 6-membered cyclic structure with reagent molecules in the transition state, in which the transfer of a proton from N-ethylaniline amino group to a hydrogen chloride molecule occurs via a relay mechanism involving the water molecule. The activation energy values of the studied processes were calculated; it is shown that both specific and universal solvation significantly lower the energy barrier of the reaction compared to the reaction occurring in gas phase, which is consistent with the data obtained earlier for related processes.

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41

Milenković, Dejan, Jelena Đorović, Edina Avdović, Žiko Milanović, and Marko Antonijević. "THERMODYNAMIC AND KINETIC INVESTIGATION OF ANTIRADICAL POTENTIAL OF CYANIDIN." Journal of the Serbian Society for Computational Mechanics, Special (June 1, 2020): 85–95. http://dx.doi.org/10.24874/jsscm.2020.01.08.

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In the present paper, M05-2X/6-311+G(d,p) level of theory was used to investigate antiradical activity of cyanidin towards highly damaging radical species (.OH, .OCH3, .OOH and .OOCH3). The applied method successfully reproduces the values of reaction enthalpies (ΔHBDE, ΔHIP, and ΔHPA). These parameters are important to determine which of the mechanisms are preferred. Reaction enthalpies related to the antioxidant mechanisms of the investigated species were calculated in water and DMSO. The enthalpies of reactions indicate the preferred radical scavenging mechanisms in polar (water) and polar aprotic (DMSO) solvents. Single- electron transfer followed by proton transfer (SET-PT) is not a favorable reaction pathway under any conditions. Both remaining mechanisms, HAT and SPLET, are suitable for the reaction of cyanidin with •OH and •OCH3 in all solvents under investigation. On the other hand, in the reaction of cyanidin with •OOH and •OOCH3, the SPLET mechanism is possible in both solvents. Simulation of the reaction of the cyanidin anion with the hydroxy radical confirmed that position 3` of Cy‒O- is the most suitable for reaction with •OH through electron transfer mechanism (ET) in both solvents.

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42

LI, RUI, YENG-TSENG WANG, and CHENG-LUNG CHEN. "COMPUTATIONAL MODELING STUDY ON METABOLISM MECHANISM OF OSELTAMIVIR." Journal of Theoretical and Computational Chemistry 12, no. 05 (August 2013): 1350037. http://dx.doi.org/10.1142/s0219633613500375.

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Oseltamivir (OTV) is widely used in the treatment of both influenza virus A and B infections. Additionally, OTV is an effective antiviral drug in treating the 2009 A ( H1N1 ) influenza virus. Clinical studies concluded that OTV is readily extensively converted to the active carboxylate metabolite after oral administration. In order to investigate the metabolism mechanism of OTV, we carried out density functional theory (DFT) quantum mechanical calculations. The molecule orbital (MO) theory and natural population analysis (NPA) were also employed to help understanding the reaction mechanism. All possible reaction pathways for OTV metabolism are considered, involving hydrolysis of ester and amide. Two mechanisms were considered in this work, viz. concerted mechanism and stepwise mechanism. Our results indicate the stepwise mechanism is more favorable in both hydrolysis reactions and the rate-determining stage is the formation of the tetrahedral intermediate. In addition, the hydrolysis reactions can be assisted by substrate NH2 group and solvent water molecules. The substrate-assisted mechanism for the formation of the carboxylate metabolite is the most favorable one.

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43

Fujisawa, K., S. Yasui, and Y. Moro-oka. "Reaction mechanism of tyrosinase catalysis." Journal of Inorganic Biochemistry 67, no. 1-4 (July 1997): 74. http://dx.doi.org/10.1016/s0162-0134(97)89955-2.

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44

Andreou, Alexandra, and Ivo Feussner. "Lipoxygenases – Structure and reaction mechanism." Phytochemistry 70, no. 13-14 (September 2009): 1504–10. http://dx.doi.org/10.1016/j.phytochem.2009.05.008.

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45

Buxbaum, Engelbert, and Philip G. Woodman. "90 Reaction mechanism of Hsc70." Biochemical Society Transactions 23, no. 4 (November 1, 1995): 557S. http://dx.doi.org/10.1042/bst023557s.

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46

Zhang, Ruibo, Tesfaye A. Abtew, Nicholas F. Quackenbush, Linda W. Wangoh, Matthew Huie, Alexander B. Brady, David Bock, et al. "Electrode Reaction Mechanism of Ag2VO2PO4Cathode." Chemistry of Materials 28, no. 10 (May 13, 2016): 3428–34. http://dx.doi.org/10.1021/acs.chemmater.6b00828.

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47

Blass, K. G. "The entire Jaffé reaction mechanism." Clinical Biochemistry 33, no. 3 (April 2000): 225–26. http://dx.doi.org/10.1016/s0009-9120(00)00087-4.

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48

Ozturk, N., C. P. Selby, Y. Annayev, D. Zhong, and A. Sancar. "Reaction mechanism of Drosophila cryptochrome." Proceedings of the National Academy of Sciences 108, no. 2 (December 27, 2010): 516–21. http://dx.doi.org/10.1073/pnas.1017093108.

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49

Córdoba, José M., María J. Sayagués, María D. Alcalá, and Francisco J. Gotor. "Synthesis of Ti3SiC2Powders: Reaction Mechanism." Journal of the American Ceramic Society 90, no. 3 (March 2007): 825–30. http://dx.doi.org/10.1111/j.1551-2916.2007.01501.x.

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50

Lee, T. S. H. "Mechanism ofHe3(π−,pn) reaction." Physical Review C 31, no. 6 (June 1, 1985): 2163–67. http://dx.doi.org/10.1103/physrevc.31.2163.

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