Photocatalytic Decomposition of Metoprolol and Its Intermediate Organic Reaction Products: Kinetics and Degradation Pathway

2016 ◽  
Vol 14 (3) ◽  
pp. 809-820 ◽  
Author(s):  
Alfonso Pinedo ◽  
Mariana López ◽  
Elisa Leyva ◽  
Brenda Zermeño ◽  
Benito Serrano ◽  
...  
Keyword(s):  
Uv Light ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Initial Reaction Rate ◽  
Degradation Pathway ◽  
Photocatalytic Decomposition ◽  
Initial Reaction ◽  
Low Molecular Weight ◽  
Reaction Products ◽  
Constant Flow Rate

Abstract High purity metoprolol prepared by neutralization of an aqueous solution of metoprolol tartrate is efficiently mineralized to CO2 and water by photocatalysis with TiO2, UV light and a constant flow rate of oxygen. Since the tartrate anions were eliminated, all the HO• generated by photocatalysis reacted efficiently with the aromatic part of the medication. The reaction pathway includes two routes of degradation. The first one includes the transformation of metoprolol to hydroquinone via formation of 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde. Metoprolol is also degraded directly to hydroquinone. Then, this aromatic compound is oxidized to 1,2,4-benzenetriol, which is rapidly oxidized to low molecular weight organic acids before being completely mineralized to CO2 and water. Kinetic studies indicated that the initial reaction rate of the degradation of metoprolol, 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde is described by the LH-HW model.

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.

scholarly journals Optimal Design of Experiments for Hybrid Nonlinear Models, with Applications to Extended Michaelis–Menten Kinetics

2020 ◽  
Vol 25 (4) ◽  
pp. 601-616 ◽  
Author(s):  
Yuanzhi Huang ◽  
Steven G. Gilmour ◽  
Kalliopi Mylona ◽  
Peter Goos
Keyword(s):  
Optimal Design ◽  
Nonlinear Models ◽  
Nonlinear Least Squares ◽  
Kinetic Studies ◽  
Initial Reaction Rate ◽  
Industrial Applications ◽  
Design Criterion ◽  
Initial Reaction ◽  
Wide Range ◽  
Nonlinear Least Squares Estimation

Abstract Biochemical mechanism studies often assume statistical models derived from Michaelis–Menten kinetics, which are used to approximate initial reaction rate data given the concentration level of a single substrate. In experiments dealing with industrial applications, however, there are typically a wide range of kinetic profiles where more than one factor is controlled. We focus on optimal design of such experiments requiring the use of multifactor hybrid nonlinear models, which presents a considerable computational challenge. We examine three different candidate models and search for tailor-made D- or weighted-A-optimal designs that can ensure the efficiency of nonlinear least squares estimation. We also study a compound design criterion for discriminating between two candidate models, which we recommend for design of advanced kinetic studies. Supplementary materials accompanying this paper appear on-line

scholarly journals Photocatalytic degradation of Bisphenol A: Kinetic studies and determination of the reaction pathway

2018 ◽  
Vol 16 (5) ◽  
Author(s):  
Luis F. Garay Rodríguez ◽  
Brenda Zermeño ◽  
Karla Alejandra López De la O ◽  
Elisa Leyva ◽  
Edgar Moctezuma
Keyword(s):  
Aqueous Solutions ◽  
Photocatalytic Degradation ◽  
Reaction Rate ◽  
Reaction Pathway ◽  
Batch Reactor ◽  
Analytical Techniques ◽  
Kinetic Studies ◽  
Degradation Process ◽  
Reaction Products ◽  
Uv Lamps

The photocatalytic degradation of BPA aqueous solutions with commercial TiO2 (Evonik P25) was carried out in a home-made batch reactor illuminated with four UV lamps (λmax= 365 nm) in order to determine the kinetic parameters of the reaction rate equation and to identify and quantify some of the most stable aromatic intermediate reaction products. Low concentration (20 ppm) BPA solutions were completely degraded and mineralized in less than three hours of reaction. Whereas, BPA aqueous solutions with concentration above 50 ppm are transformed in other chemical compounds in 6 hours of reaction and fully mineralized in 15 hours of reaction. Kinetic analysis of the experimental results of BPA concentration as a function of time indicated that this photocatalytic degradation process follows a LH-HW reaction rate law where the reaction order shift from zero order to first order as the reactant concentration is decreased. Analysis of the reaction samples by different analytical techniques indicated that BPA is mineralized via formation of hydroquinone, benzoquinone, benzene-triol, catechol, and phenol by two simultaneous reaction pathways.

scholarly journals Removal of 1,4-Naphthoquinone by Birnessite-Catalyzed Oxidation: Effect of Phenolic Mediators and the Reaction Pathway

2020 ◽  
Vol 17 (13) ◽  
pp. 4853
Author(s):  
Han-Saem Lee ◽  
Jin Hur ◽  
Doo-Hee Lee ◽  
Mark A. Schlautman ◽  
Hyun-Sang Shin
Keyword(s):  
Reaction Pathway ◽  
Removal Rate ◽  
Coupling Reaction ◽  
Initial Reaction ◽  
Limiting Factor ◽  
Reaction Products ◽  
Hammett Constant ◽  
Cross Coupling Reaction ◽  
Liquid Chromatography Tandem Mass ◽  
Catalyzed Oxidation

This study investigated the birnessite (δ-MnO2) catalyzed oxidative removal of 1,4-naphthoquinone (1,4-NPQ) in the presence of phenolic mediators; specifically, the kinetics of 1,4-NPQ removal under various conditions was examined, and the reaction pathway of 1,4-NPQ was verified by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The removal rate of 1,4-NPQ by birnessite-catalyzed oxidation (pH = 5) was faster in the presence of phenolic mediators with electron-donating substituents (pseudo-first-order initial stage rate constant (k1) = 0.380–0.733 h−1) than with electron-withdrawing substituents (k1 = 0.071–0.244 h−1), and the effect on the substituents showed a positive correlation with the Hammett constant (Σσ) (r2 = 0.85, p < 0.001). The rate constants obtained using variable birnessite loadings (0.1–1.0 g L−1), catechol concentrations (0.1–1.0 mM), and reaction sequences indicate that phenolic mediators are the major limiting factor for the cross-coupling reaction of 1,4-NPQ in the initial reaction stages, whereas the birnessite-catalyzed surface reaction acts as the major limiting factor in the later reaction stages. This was explained by the operation of two different reaction mechanisms and reaction products identified by LC-MS/MS.

2-Mercaptothiazole and Derivatives as Vulcanization Accelerators

1962 ◽  
Vol 35 (5) ◽  
pp. 1360-1429 ◽  
Author(s):  
C. D. Trivette ◽  
E. Morita ◽  
E. J. Young
Keyword(s):  
Experimental Data ◽  
Kinetic Studies ◽  
Thiol Group ◽  
Zinc Stearate ◽  
Side Reactions ◽  
Initial Reaction ◽  
Reaction Products ◽  
Technical Literature ◽  
Free Thiol Group ◽  
The Individual

Abstract In this paper the subject of rubber vulcanization accelerated by 2-mercapto-benzothiazole and its derivatives has been reviewed. The technical literature from 1945 through 1960 and patents from 1932 through 1960 have been covered. Topics include: methods of synthesis and manufacture of these accelerators; application and compounding data on their use in rubber processing; and studies of the modes of action and mechanisms for the chemical reactions involved during accelerated vulcanization. Much disagreement exists concerning the mechanism of accelerated vulcanization and the action of thiazole accelerators. However, most of the conflict lies not in the experimental data collected, but in the interpretation of the meaning of the data. It is well documented that MBT and activators (zinc stearate, or zinc oxide and stearic acid) undergo an initial reaction; that these reaction products then react with sulfur and/or rubber hydrocarbon to form intermediate compounds; and that these intermediates then react in some manner to form sulfur crosslinks. Not known, for the most part, are the precise reaction steps involved; the sequence in which these reactions occur; the individual mechanisms, whether ionic, free radical, or neither, by which these reactions proceed; and the side reactions involved, if any (except in natural rubber, in which the non-crosslink forming cyclization reaction is well documented) which might lead to erroneous conclusions from the experimental data, particularly from kinetic studies. These same conclusions apply in general to thiazole sulfenamide accelerated sulfur vulcanization, with the exception that, in contrast to MBT, which has a free thiol group available for immediate reaction, the sulfenamide must first decompose or react in some manner before acceleration occurs. Sulfur and divalent sulfur compounds readily undergo both radical and ionic reactions, depending only on co-reactants and reaction conditions. At present, the reactions of sulfur with hydrocarbons and accelerators are not sufficiently well understood to draw concrete conclusions about the mechanism of acceleration. Further progress on elucidation of the mechanism will come with a better knowledge of the chemistry and mechanisms of sulfur reactions.

The Kinetics of Inhibition of the Action of Thrombin by the Fibrinopeptides Formed during the Clotting of Fibrinogen

1966 ◽  
Vol 16 (01/02) ◽  
pp. 277-295 ◽  
Author(s):  
A Silver ◽  
M Murray
Keyword(s):  
Amino Acids ◽  
Competitive Inhibition ◽  
Amorphous Material ◽  
Peptide Bond ◽  
Initial Reaction ◽  
Reaction Products ◽  
Coagulation Mechanism ◽  
Kinetics Of ◽  
Kinetics Of Inhibition ◽  
Burk Plot

SummaryVarious investigators have separated the coagulation products formed when fibrinogen is clotted with thrombin and identified fibrinopeptides A and B. Two other peaks are observed in the chromatogram of the products of coagulation, but these have mostly been dismissed by other workers. They have been identified by us as amino acids, smaller peptides and amorphous material (37). We have re-chromatographed these peaks and identified several amino acids. In a closed system of fibrinogen and thrombin, the only reaction products should be fibrin and peptide A and peptide B. This reasoning has come about because thrombin has been reported to be specific for the glycyl-arginyl peptide bond. It is suggested that thrombin also breaks other peptide linkages and the Peptide A and Peptide B are attacked by thrombin to yield proteolytic products. Thrombin is therefore probably not specific for the glycyl-arginyl bond but will react on other linkages as well.If the aforementioned is correct then the fibrinopeptides A and B would cause an inhibition with the coagulation mechanism itself. We have shown that an inhibition does occur. We suggest that there is an autoinhibition to the clotting mechanism that might be a control mechanism in the human body.The experiment was designed for coagulation to occur under controlled conditions of temperature and time. Purified reactants were used. We assembled an apparatus to record visually the speed of the initial reaction, the rate of the reaction, and the density of the final clot formed after a specific time.The figures we derived made available to us data whereby we could calculate and plot the information to show the mechanism and suggest that such an inhibition does exist and also further suggest that it might be competitive.In order to prove true competitive inhibition it is necessary to fulfill the criteria of the Lineweaver-Burk plot. This has been done. We have also satisfied other criteria of Dixon (29) and Bergman (31) that suggest true competitive inhibition.

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.

scholarly journals Self-Assembled Bimetallic Aluminum-Salen Catalyst for the Cyclic Carbonates Synthesis

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4097
Author(s):  
Wooyong Seong ◽  
Hyungwoo Hahm ◽  
Seyong Kim ◽  
Jongwoo Park ◽  
Khalil A. Abboud ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Cyclic Carbonate ◽  
Reaction Conditions ◽  
Formation Reaction ◽  
X Ray ◽  
Carbonate Formation ◽  
Salen Aluminum

Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO2. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.

scholarly journals Biochar Chemistry in a Weathered Tropical Soil: Kinetics of Phosphorus Sorption

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 295
Author(s):  
Marina Moura Morales ◽  
Nicholas Brian Comerford ◽  
Maurel Behling ◽  
Daniel Carneiro de Abreu ◽  
Iraê Amaral Guerrini
Keyword(s):  
Mineral Soil ◽  
Soil Surface ◽  
Kinetic Studies ◽  
Inorganic Phosphorus ◽  
Initial Reaction ◽  
Phosphorus Sorption ◽  
P Sorption ◽  
Published Research ◽  
Kinetics Of

The phosphorus (P) chemistry of biochar (BC)-amended soils is poorly understood. This statement is based on the lack of published research attempting a comprehensive characterization of biochar’s influence on P sorption. Therefore, this study addressed the kinetic limitations of these processes. This was accomplished using a fast pyrolysis biochar made from a mix of waste materials applied to a highly weathered Latossolo Vermelho distrofico (Oxisol) from São Paulo, Brazil. Standard method (batch method) was used. The sorption kinetic studies indicated that P sorption in both cases, soil (S) and soil-biochar (SBC), had a relatively fast initial reaction between 0 to 5 min. This may have happened because adding biochar to the soil decreased P sorption capacity compared to the mineral soil alone. Presumably, this is a result of: (i) Inorganic phosphorus desorbed from biochar was resorbed onto the mineral soil; (ii) charcoal particles physically covered P sorption locations on soil; or (iii) the pH increased when BC was added SBC and the soil surface became more negatively charged, thus increasing anion repulsion and decreasing P sorption.

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.

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