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.

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 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.

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.

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.

scholarly journals T181. PROTEIN ACYL-THIOESTERASE ENZYME ACTIVITY IN THE POSTMORTEM DORSOLATERAL PREFRONTAL CORTEX IN SCHIZOPHRENIA

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S300-S301
Author(s):  
Shaun Hopper ◽  
James Meador-Woodruff
Keyword(s):  
Prefrontal Cortex ◽  
Total Protein ◽  
Protein Trafficking ◽  
Dorsolateral Prefrontal Cortex ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Tissue Homogenate ◽  
Initial Reaction ◽  
Cortical Tissue ◽  
Dorsolateral Prefrontal

Abstract Background The role protein trafficking and localization is a recent target of investigation in schizophrenia pathophysiology. An important mediator of protein trafficking is S-acylation, also known as S-palmitoylation, which is the reversible attachment of long chain fatty acids to cysteine residues. S-acylation is a dynamic post-translational modification that modulates hydrophobicity of proteins, regulating their membrane association and subcellular localization. Notably, we have previously reported a proteome-wide decrease in S-acylated protein levels in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia. One potential mechanism of decreased S-acylation is increased removal of acyl groups from proteins by protein acyl-thioesterase enzymes (PATs). Here we describe the optimization of an assay to measure the activity of the PAT family of enzymes in human postmortem cortical tissue and use the assay to address our hypothesis that PAT activity is increased in the DLPFC of subjects with schizophrenia. Methods To determine PAT activity, tissue homogenate was incubated with 4-methylumbelliferyl-6-thio-palmitate-β-D-glucopyranoside (4MU-Gluc-Palm) and 1U of exogenous β-glucosidase (to hydrolyze the 4MU-Gluc reaction intermediary). Released 4MU was excited at 360 ± 40 nm and fluorescent emission was measured, per minute, at 460 ± 40 nm. To determine the relationship between initial reaction rate and amount of enzyme, the initial reaction rate using 300 µM 4MU-Gluc-Palm was measured in homogenate containing 1 – 10 µg of total protein from the DLPFC of a subject with no history of psychiatric illness. The PAT activity of DLPFC homogenate boiled for 30 min and total protein homogenate from lymphocytes were measured as negative and positive control reactions, respectively. To estimate the maximum reaction rate (Vmax) and the concentration of 4MU-Gluc-Palm which achieved ½ Vmax (Km; a measure of enzyme-substrate affinity) the initial reaction rate was calculated in the presence of 0 – 200 µM 4MU-Gluc-Palm and the Michaelis-Menten equation was fit to plots of concentration vs. initial rate. Reactions were performed on 2.5 µg total protein homogenate from the DLPFC of 24 subjects with schizophrenia and 24 non-psychiatrically ill subjects. Results A fluorescent signal, which increases with time to a plateau upon substrate depletion, is detectable in total protein homogenate from DLPFC and lymphocytes, but not boiled DLPFC homogenate. In the DLPFC the initial reaction rate is linear with total protein amount [r2 = .99; p = .007], demonstrating that the reaction is sensitive to varying amounts of enzyme in a 10-fold range. When compared between schizophrenia and control subjects, neither Vmax [t(46) = 0.756; p = .45] nor Km [t(46) = 0.780; p = .44] were statistically significantly different. Discussion Here we have demonstrated that PAT activity is measurable in human cortical tissue homogenate. Additionally, we have found no difference in the Vmax or Km of the combined PAT enzyme group in schizophrenia, providing no evidence to support our hypothesis that total PAT activity is increased in subjects with schizophrenia. This suggests that the proteome-wide decrease in S-acylated proteins in schizophrenia is caused by another mechanism, possibly increased expression or function of one or more of the specific PATs, leading to substrate specific changes in S-acylation, or a decrease in activity the acyl protein transferase enzymes, which attach acyl groups to proteins.

The fast detection of streptavidin based on the initial reaction rate of the binding-induced DNA strand-displacement reaction

2016 ◽  
Vol 8 (37) ◽  
pp. 6701-6704 ◽  
Author(s):  
Chenxi Li ◽  
Ruoyun Lin ◽  
Tian Li ◽  
Feng Liu ◽  
Na Li
Keyword(s):  
Small Molecules ◽  
Reaction Rate ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Strand Displacement ◽  
Fast Detection ◽  
Dna Strand Displacement ◽  
Displacement Reactions ◽  
Dna Strand ◽  
Strand Displacement Reaction

Binding-induced DNA strand-displacement reactions diversify the applications beyond nucleic acids and small molecules.

scholarly journals Layer-Like Zeolite X as Catalyst in a Knoevenagel Condensation: The Effect of Different Preparation Pathways and Cation Exchange

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 474
Author(s):  
Jan-Paul Grass ◽  
Katharina Klühspies ◽  
Bastian Reiprich ◽  
Wilhelm Schwieger ◽  
Alexandra Inayat
Keyword(s):  
Catalytic Activity ◽  
Reaction Rate ◽  
Knoevenagel Condensation ◽  
Ethyl Cyanoacetate ◽  
Reaction Rates ◽  
Initial Reaction Rate ◽  
Comparative Investigation ◽  
Morphological Properties ◽  
Initial Reaction ◽  
Zeolite X

This study is dedicated to the comparative investigation of the catalytic activity of layer-like Faujasite-type (FAU) zeolite X obtained from three different synthesis routes (additive-free route, Li2CO3 route, and TPOAC route) in a liquid-phase Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate to ethyl trans-α-cyanocinnamate. It is shown that the charge-balancing cations (Na+ and K+) and the morphological properties have a strong influence on the apparent reaction rate and degree of conversion. The highest initial reaction rate could be found for the layer-like zeolite X synthesised by the additive-free route in the potassium form. In most cases, the potassium-exchanged zeolites enabled higher maximum conversions and higher reaction rates compared to the zeolite X catalysts in sodium form. However, very thin crystal plates (below 100 nm thickness), similar to those obtained in the presence of TPOAC, did not withstand the multiple aqueous ion exchange procedure, with the remaining coarse crystals facilitating less enhancement of the catalytic activity.

Sign in / Sign up

Export Citation Format

Share Document