Permanganate oxidation of glycine: Kinetics, catalytic effects, and mechanisms

1987 ◽  
Vol 65 (10) ◽  
pp. 2329-2337 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Fernando Mata-Perez ◽  
Enrique Brillas
Keyword(s):  
Catalytic Reaction ◽  
Initial Reaction Rate ◽  
Reaction Pathways ◽  
Soluble Form ◽  
Initial Reaction ◽  
Order Unity ◽  
First Order ◽  
Constant Ph ◽  
Apparent Activation Energies ◽  
Experimental Findings

The oxidation of glycine by permanganate ion in aqueous phosphate buffers is autocatalyzed by the soluble form of colloidal manganese dioxide formed as a reaction product. Both the noncatalytic and the catalytic reaction pathways are first order in permanganate, the noncatalytic pathway is also first order in glycine, whereas the catalytic pathway has a kinetic order unity for the autocatalytic agent and a non-integral order (1.31) for glycine. Both reaction pathways are accelerated by an increase in the pH of the medium, whereas an increase in the buffer concentration at constant pH results in an increase in the rate of the noncatalytic pathway and a decrease in the rate of the catalytic one. Additions of potassium chloride to the solutions have no kinetic effect on the reaction. The apparent activation energies of the noncatalytic and catalytic reaction pathways are 64.5 and 62.0 kJ mol−1, respectively. On the other hand, manganese(II), thiosulfate, and hexacyanoferrate(II) ions, as well as benzyltriethylammonium chloride and arabic gum, have all been found to increase the initial reaction rate. Mechanisms in concordance with the experimental findings are proposed.

Kinetische Untersuchung der Methanolyse von chlormethylierten Phenolen / Kinetic Studies of the Methanolysis Reaction of Chloromethylated Phenols

1981 ◽  
Vol 36 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Günter Steina ◽  
Volker Böhmer ◽  
Werner Lötz ◽  
Hermann Kämmerer
Keyword(s):  
Reaction Rate ◽  
Sharp Decrease ◽  
Kinetic Studies ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Phenolic Hydroxy Group ◽  
First Order ◽  
First Order Kinetics ◽  
Reaction Constants ◽  
Phenolic Hydroxy

Abstract The solvolysis of 25 differently substituted chloromethylated phenols was studied kinetically in methanol at 25 °C. A sharp decrease of the initial reaction rate with in-creasing concentrations of added acids can be explained by a very fast solvolysis of the phenolate anions in comparison with the undissociated compounds. The latter show strictly first order kinetics up to high conversions and the rate constants can be partly correlated with the Jaffé relation. Highly negative values for the reaction constants q = -5.4 and q = -6.2 for ortho-and para-chloromethylated compounds show, that the undissociated phenols react according to the SNl -mechanism. However, deviations are found for compounds with strongly electron attracting substituents, which may be partly caused by an intramolecular catalytic effect of the phenolic hydroxy group in the case of the ortho-isomers.

Reduction of benzylideneacetone derivatives with Pd/SiO2–AlPO4 as catalyst and cyclohexene as hydrogen donor

1984 ◽  
Vol 62 (5) ◽  
pp. 917-921 ◽  
Author(s):  
A. Alba ◽  
A. Aramendia ◽  
V. Borau ◽  
A. Garcia-Raso ◽  
C. Jimenez ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
Reaction Rate ◽  
Hydrogen Transfer ◽  
Selective Reduction ◽  
Initial Reaction Rate ◽  
Hydrogen Donor ◽  
Initial Reaction ◽  
First Order ◽  
Donor And Acceptor

The hydrogen transfer reduction of benzylideneacetone derivatives p-X-C6H4—CH=CH—CO—R (X = —OCH3, H; R = C6H5, alkyl, OR, OH) using cyclohexene as hydrogen donor has been studied. The selective reduction of the C=C bond is observed and the effects of the nature of X and R, solvent, catalyst, and reaction temperature on the initial reaction rate are analyzed. In all cases, and for any substrate or catalyst, the reaction is first-order with respect to the hydrogen donor and acceptor.

scholarly journals Promising Immobilization of Industrial-Class Phospholipase A1 to Attain High-Yield Phospholipids Hydrolysis and Repeated Use with Optimal Water Content in Water-in-Oil Microemulsion Phase

2021 ◽  
Vol 11 (4) ◽  
pp. 1456
Author(s):  
Yusuke Hayakawa ◽  
Ryoichi Nakayama ◽  
Norikazu Namiki ◽  
Masanao Imai
Keyword(s):  
Water Content ◽  
Reaction Rate ◽  
Enzyme Reaction ◽  
Initial Reaction Rate ◽  
Industrial Applications ◽  
Molar Ratio ◽  
High Yield ◽  
Initial Reaction ◽  
Phospholipase A1 ◽  
Repeated Use

In this study, we maximized the reactivity of phospholipids hydrolysis with immobilized industrial-class phospholipase A1 (PLA1) at the desired water content in the water-in-oil (W/O) microemulsion phase. The optimal hydrophobic-hydrophilic condition of the reaction media in a hydrophobic enzyme reaction is critical to realize the maximum yields of enzyme activity of phospholipase A1. It was attributed to enzymes disliking hydrophobic surroundings as a special molecular structure for reactivity. Immobilization of PLA1 was successfully achieved with the aid of a hydrophobic carrier (Accurel MP100) combination with the treatment using glutaraldehyde. The immobilized yield was over 90% based on simple adsorption. The hydrolysis reaction was kinetically investigated through the effect of glutaraldehyde treatment of carrier and water content in the W/O microemulsion phase. The initial reaction rate increased linearly with an increasing glutaraldehyde concentration and then leveled off over a 6% glutaraldehyde concentration. The initial reaction rate, which was predominantly driven by the water content in the organic phase, changed according to a typical bell-shaped curve with respect to the molar ratio of water to phospholipid. It behaved in a similar way with different glutaraldehyde concentrations. After 10 cycles of repeated use, the reactivity was well sustained at 40% of the initial reaction rate and the creation of the final product. Accumulated yield after 10 times repetition was sufficient for industrial applications. Immobilized PLA1 has demonstrated potential as a biocatalyst for the production of phospholipid biochemicals.

Ensemble Learning Approach with LASSO for Predicting Catalytic Reaction Rates

Synlett ◽  
2020 ◽  
Author(s):  
Akira Yada ◽  
Kazuhiko Sato ◽  
Tarojiro Matsumura ◽  
Yasunobu Ando ◽  
Kenji Nagata ◽  
...  
Keyword(s):  
Ensemble Learning ◽  
Reaction Rates ◽  
Initial Reaction Rate ◽  
Training Dataset ◽  
Initial Reaction ◽  
Learning Approach ◽  
Learning Framework ◽  
Machine Learning Approach ◽  
Reasonable Prediction ◽  
Epoxidation Of Alkenes

AbstractThe prediction of the initial reaction rate in the tungsten-catalyzed epoxidation of alkenes by using a machine learning approach is demonstrated. The ensemble learning framework used in this study consists of random sampling with replacement from the training dataset, the construction of several predictive models (weak learners), and the combination of their outputs. This approach enables us to obtain a reasonable prediction model that avoids the problem of overfitting, even when analyzing a small dataset.

Co-processing of hydrodeoxygenation and hydrodesulfurization of phenol and dibenzothiophene with NiMo/Al2O3–ZrO2 and NiMo/TiO2–ZrO2 catalysts

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jesús Andrés Tavizón Pozos ◽  
Gerardo Chávez Esquivel ◽  
Ignacio Cervantes Arista ◽  
José Antonio de los Reyes Heredia ◽  
Víctor Alejandro Suárez Toriello
Keyword(s):  
Active Sites ◽  
Reaction Rate ◽  
Supported Catalysts ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Competition Effect ◽  
Support Interaction ◽  
Highly Active ◽  
Metal Support Interaction ◽  
Metal Support

Abstract The influence of Al2O3–ZrO2 and TiO2–ZrO2 supports on NiMo-supported catalysts at a different sulfur concentration in a model hydrodeoxygenation (HDO)-hydrodesulfurization (HDS) co-processing reaction has been studied in this work. A competition effect between phenol and dibenzothiophene (DBT) for active sites was evidenced. The competence for the active sites between phenol and DBT was measured by comparison of the initial reaction rate and selectivity at two sulfur concentrations (200 and 500 ppm S). NiMo/TiO2–ZrO2 was almost four-fold more active in phenol HDO co-processed with DBT than NiMo/Al2O3–ZrO2 catalyst. Consequently, more labile active sites are present on NiMo/TiO2–ZrO2 than in NiMo/Al2O3–ZrO2 confirmed by the decrease in co-processing competition for the active sites between phenol and DBT. DBT molecules react at hydrogenolysis sites (edge and rim) preferentially so that phenol reacts at hydrogenation sites (edge and edge). However, the hydrogenated capacity would be lost when the sulfur content was increased. In general, both catalysts showed similar functionalities but different degrees of competition according to the highly active NiMoS phase availability. TiO2–ZrO2 as the support provided weaker metal-support interaction than Al2O3–ZrO2, generating a larger fraction of easily reducible octahedrally coordinated Mo- and Ni-oxide species, causing that NiMo/TiO2–ZrO2 generated precursors of MoS2 crystallites with a longer length and stacking but with a higher degree of Ni-promotion than NiMo/Al2O3–ZrO2 catalyst.

scholarly journals Exploring Coupled Redox and pH Processes with a Force Field-Based Approach: Applications to Five Different Systems

2020 ◽  
Author(s):  
Vinicius Cruzeiro ◽  
Gustavo Troiano Feliciano ◽  
Adrian Roitberg
Keyword(s):  
Force Field ◽  
Redox Potential ◽  
Desulfovibrio Vulgaris ◽  
Cytochrome C3 ◽  
Computational Tools ◽  
Redox States ◽  
Computational Performance ◽  
Redox Active ◽  
Constant Ph ◽  
Experimental Findings

Coupled redox and pH-driven processes are at the core of many important biological mechanisms. As the distribution of protonation and redox states in a system is associated with the pH and redox potential of the solution, having efficient computational tools that can simulate under these conditions become very important. Such tools have the potential to provide information that complement and drive experiments. In previous publications we have presented the implementation of the constant pH and redox potential molecular dynamics (C(pH,E)MD) method in AMBER and we have shown how multidimensional replica exchange can be used to significantly enhance the convergence efficiency of our simulations. In the current work, after an improvement in our C(pH,E)MD approach that allows a given residue to be simultaneously pH- and redox-active, we have employed our methodologies to study five different systems of interest in the literature. We present results for: capped tyrosine dipeptide, two maquette systems containing one pH- and redox-active tyrosine (α3Y and peptide A), and two proteins that contain multiple heme groups (diheme cytochrome c from Rhodobacter sphaeroides and Desulfovibrio vulgaris Hildenborough cytochrome c3). We show that our results can provide new insights into previous theoretical and experimental findings by using a fully force field-based and GPUaccelerated approach, which allows the simulations to be executed with high computational performance.

scholarly journals Revisiting Catalytic Cycles: A Broader View Through the Energy Span Model

2020 ◽  
Author(s):  
Diego Garay-Ruiz ◽  
Carles Bo
Keyword(s):  
Catalytic Reaction ◽  
Reaction Mechanisms ◽  
Computational Study ◽  
Reaction Network ◽  
Co2 Hydrogenation ◽  
Level Of Detail ◽  
Reaction Pathways ◽  
Catalytic Systems ◽  
Computational Code ◽  
Catalytic Cycles

<div><div><div><p>The computational study of catalytic processes allows discovering really intricate and detailed reaction mechanisms that involve many species and transformations. This increasing level of detail can even result detrimental when drawing conclusions from the computed mechanism, as many co-existing reaction pathways can be in close com- petence. Here we present a reaction network-based implementation of the energy span model in the form of a computational code, gTOFfee, capable of dealing with any user-specified reaction network. This approach, compared to microkinetic simulations, enables a much easier and straightforward analysis of the performance of any catalytic reaction network. In this communication, we will go through the foundations and appli- cability of the underlying model, and will tackle the application to two relevant catalytic systems: homogeneous Co-mediated propene hydroformylation and heterogeneous CO2 hydrogenation over Cu(111).</p></div></div></div>

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