scholarly journals Tandem buildup of complexity of aromatic molecules through multiple successive electrophile generation in one pot, controlled by varying the reaction temperature

2016 ◽  
Vol 14 (5) ◽  
pp. 1680-1693 ◽  
Author(s):  
Akinari Sumita ◽  
Yuko Otani ◽  
Tomohiko Ohwada
Keyword(s):  
Reaction Temperature ◽  
Reaction System ◽  
Reaction Rates ◽  
Aromatic Molecule ◽  
One Pot ◽  
Aromatic Molecules

The unmasking reaction rates and the time of generation of highly reactive electrophiles can be controlled. This reaction system demonstrates the conceptual validity of one-pot build-up of a complex aromatic molecule from multiple starting components.

Experimental and reaction kinetic investigation of 1-octene metathesis reaction with Hoveyda-Grubbs first generation precatalyst

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Percy van der Gryp ◽  
Sanette Marx ◽  
Hermanus C.M. Vosloo
Keyword(s):  
Reaction Temperature ◽  
First Generation ◽  
Reaction System ◽  
Reaction Rates ◽  
Product Distribution ◽  
Molar Ratio ◽  
Distribution Data ◽  
Metathesis Reaction ◽  
Pseudo First Order Reaction ◽  
Catalyst Load

Abstract In this work, we report the catalytic performance of the first generation Hoveyda-Grubbs precatalyst for the metathesis reaction of 1-octene. The reaction temperature (30 to 100°C) and catalyst load (1-octene/Ru molar ratio 5,000 to 10,000) were varied and quantities such as product distribution, activity and selectivity were evaluated. Reaction temperature showed a significant effect and turn over numbers as high as 4458 were observed for this system. Two competing mechanisms were observed for temperatures above 60°C, namely metathesis and isomerisation. The experimental product-time distribution data for the complex parallel reaction system was fairly accurately described by three elementary pseudo-first order reaction rates. The effects of temperature (Arrhenius Equation) and catalyst load were incorporated in the observed rate constant. The observed activation energies were around 10 kcal/mol.

scholarly journals Nickel Supported Natural Zeolite as a Bifunctional Catalysts for Conversion of Citronella Oil Crude to Menthols

2017 ◽  
Vol 18 (02) ◽  
pp. 132-138
Author(s):  
Ralentri Pertiwi ◽  
Silvester Tursiloadi ◽  
Indri Badria Adilina ◽  
Kiky Corneliasari Sembiring ◽  
Yuya Oaki
Keyword(s):  
Catalytic Activity ◽  
Reaction Temperature ◽  
Natural Zeolite ◽  
Reaction System ◽  
Bifunctional Catalyst ◽  
Bifunctional Catalysts ◽  
Acid Activation ◽  
Reaction Products ◽  
One Pot ◽  
Citronella Oil

Characterization and catalytic activity of modified natural zeolite for the conversion of citronella oil to menthol was investigated. In this research, natural zeolite was prepared by acid activation with HCl and impregnated with Ni metal. The addition of Ni metal of around 12.5 nm in diameter provided a bifunctional catalyst for two steps of citronella oil conversion i.e. cyclization and hydrogenation. The process was performed in a one-pot reaction system by stirring at 200oC with pressure of 20 bar H2 for 3h. The reaction products changed slightly with varieties of reaction temperature and amount of catalysts employed. Results showed that Ni/NZB-HT catalyst was the best catalyst which was able to convert citronella oil to menthol with a selectivity of 50% menthol and 100% conversion of citronellal.

scholarly journals Glucuronides Hydrolysis by Intestinal Microbial β-Glucuronidases (GUS) Is Affected by Sampling, Enzyme Preparation, Buffer pH, and Species

Pharmaceutics ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1043
Author(s):  
Christabel Ebuzoeme ◽  
Imoh Etim ◽  
Autumn Ikimi ◽  
Jamie Song ◽  
Ting Du ◽  
...  
Keyword(s):  
Enzyme Preparation ◽  
Reaction System ◽  
Reaction Rates ◽  
Experimental Conditions ◽  
Model Animal ◽  
Fresh Feces ◽  
Time Buffer ◽  
Exogenous Compounds ◽  
Activity Loss ◽  
The Impact

Glucuronides hydrolysis by intestinal microbial β-Glucuronidases (GUS) is an important procedure for many endogenous and exogenous compounds. The purpose of this study is to determine the impact of experimental conditions on glucuronide hydrolysis by intestinal microbial GUS. Standard probe 4-Nitrophenyl β-D-glucopyranoside (pNPG) and a natural glucuronide wogonoside were used as the model compounds. Feces collection time, buffer conditions, interindividual, and species variations were evaluated by incubating the substrates with enzymes. The relative reaction activity of pNPG, reaction rates, and reaction kinetics for wogonoside were calculated. Fresh feces showed the highest hydrolysis activities. Sonication increased total protein yield during enzyme preparation. The pH of the reaction system increased the activity in 0.69–1.32-fold, 2.9–12.9-fold, and 0.28–1.56-fold for mouse, rat, and human at three different concentrations of wogonoside, respectively. The Vmax for wogonoside hydrolysis was 2.37 ± 0.06, 4.48 ± 0.11, and 5.17 ± 0.16 μmol/min/mg and Km was 6.51 ± 0.71, 3.04 ± 0.34, and 0.34 ± 0.047 μM for mouse, rat, and human, respectively. The inter-individual difference was significant (4–6-fold) using inbred rats as the model animal. Fresh feces should be used to avoid activity loss and sonication should be utilized in enzyme preparation to increase hydrolysis activity. The buffer pH should be appropriate according to the species. Inter-individual and species variations were significant.

Sulfidation Experiments in a Pressurized Thermogravimetric Analyzer With Chinese Calcined Limestones

2005 ◽  
Author(s):  
Zhanlong Song ◽  
Mingyao Zhang
Keyword(s):  
Partial Pressure ◽  
Reaction Temperature ◽  
Total Pressure ◽  
Volume Fraction ◽  
Nitrogen Adsorption ◽  
Reaction Rates ◽  
Thermogravimetric Analyzer ◽  
Morphological Studies ◽  
Shrinking Core ◽  
Structure Properties

The sulfidation experiments with two kinds of Chinese calcined limestones were performed in a pressurized thermogravimetric analyzer (PTGA). The effects of reaction temperature (700–950°C), total pressure (0–1MPa), particle size (0.055–2mm), and H2S concentration (0.1–4%) on the sorbent conversions were analyzed. Morphological studies with scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) equipment were made to obtain the pictures of solid surface and of the cross-sectioned samples. Nitrogen adsorption measurements were applied to determine the pore structure properties of the particles. Experimental results show that the sulfidation rate increases with total pressure when the volume fraction of H2S is constant. However, the rate of sulfidation decreases with the increase of total pressure when the H2S partial pressure is constant. Reaction temperature affects the sulfidation greatly, and the reaction rate increases with temperature. The sulfidation is the first order with respect to H2S partial pressure. Moreover, larger particles result in lower conversions and reaction rates. The unreacted shrinking core model was applied to describe the sulfidation to determine the kinetic parameters.

scholarly journals Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by in-situ FT-IR Spectroscopy

2019 ◽  
Author(s):  
Xi Yang
Keyword(s):  
Ir Spectroscopy ◽  
Reaction Rate ◽  
Interfacial Polymerization ◽  
Reaction System ◽  
Reaction Rates ◽  
Water Permeation ◽  
Ft Ir ◽  
Trimesoyl Chloride ◽  
Ft Ir Spectroscopy

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize the nanofiltration (NF) membrane. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies are applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer; (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in-situ FT-IR spectroscopy was firstly used to monitor the IP reaction of PIP/TMC reaction system, with hydrophilic interlayers or macromolecular additives. Moreover, we study the formed polyamide layer growth on the substrate, in a real-time manner. The in-situ FT-IR experimental results confirm that the IP reaction rates are effectively suppressed and the formed polyamide thickness reduces from 138±24 nm to 46±2 nm. Furthermore, the optimized NF membrane with excellent performance are consequently obtained, which include the boosted water permeation flux about 141~238 (L·m2·h/MPa) and superior salt rejection of Na2SO4 > 98.4%.

Preparation of Nanosize Anatase TiO2 Powders by Hydrothermal Synthesis

2007 ◽  
Vol 336-338 ◽  
pp. 2017-2020 ◽  
Author(s):  
Fan Yong Ran ◽  
Wen Bin Cao ◽  
Yan Hong Li ◽  
Xiao Ning Zhang
Keyword(s):  
Grain Size ◽  
Hydrothermal Synthesis ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Reaction Temperature ◽  
Reaction System ◽  
Anatase Tio2 ◽  
Holding Time ◽  
Precursor Concentration

Nanosize anatase TiO2 powders have been synthesized by hydrothermal synthesis by using technical grade TiOSO4 as precursor and urea as precipitating agent. The initial pressure of the reaction system was set at 6 MPa. Stirring speed was fixed at 300r/min. The reaction system reacted at the temperature ranged from 110 to 150°C for holding 2hrs to 8hrs and the concentration of the precursor was ranged from 0.25M to1.5M. XRD patterns show that the synthesized powders are in the form of anatase phase. Calculated grain size is ranged from 6.7 to 8.9nm by Scherrer method from the line broadening of the (101) diffraction peak of anatase. The specific surface area of the powders synthesized under different conditions is ranged from 124 to 240m2/g. The grain size of the powders increases with the increase of the reaction temperature, holding time and precursor concentration, respectively. The specific surface area decreases with the increase of reaction temperature and holding time, and does not obviously change with the change of precursor concentration when the concentration of the precursor is less than 1M. However, when the concentration is higher than 1M, the specific surface area will decrease quickly with the increase of the precursor concentration. XRD and DSC-TG analysis shows that the synthesized anatase TiO2 will begin to transform to rutile TiO2 at about 840°C. When heated to 1000°C for holding 1h, the anatase powders will transform to rutile completely.

scholarly journals Coarse-graining via EDP-convergence for linear fast-slow reaction systems

2020 ◽  
Vol 30 (09) ◽  
pp. 1765-1807 ◽  
Author(s):  
Alexander Mielke ◽  
Artur Stephan
Keyword(s):  
Detailed Balance ◽  
Reaction System ◽  
Gradient Flow ◽  
Coarse Graining ◽  
Reaction Rates ◽  
Coarse Grained ◽  
Gradient Structure ◽  
Reaction Systems ◽  
Fast Reactions ◽  
Finite State

We consider linear reaction systems with slow and fast reactions, which can be interpreted as master equations or Kolmogorov forward equations for Markov processes on a finite state space. We investigate their limit behavior if the fast reaction rates tend to infinity, which leads to a coarse-grained model where the fast reactions create microscopically equilibrated clusters, while the exchange mass between the clusters occurs on the slow time scale. Assuming detailed balance the reaction system can be written as a gradient flow with respect to the relative entropy. Focusing on the physically relevant cosh-type gradient structure we show how an effective limit gradient structure can be rigorously derived and that the coarse-grained equation again has a cosh-type gradient structure. We obtain the strongest version of convergence in the sense of the Energy-Dissipation Principle (EDP), namely EDP-convergence with tilting.

scholarly journals Zinc Chloride Catalyzed Amino Claisen Rearrangement of 1-N-Allylindolines: An Expedient Protocol for the Synthesis of Functionalized 7-Allylindolines

2019 ◽  
Vol 25 (1) ◽  
pp. 22-26 ◽  
Author(s):  
Seema Jain
Keyword(s):  
Zinc Chloride ◽  
Claisen Rearrangement ◽  
Reaction System ◽  
Biologically Active ◽  
Catalyst Loading ◽  
One Pot ◽  
Substitution Pattern ◽  
Claisen Rearrangements ◽  
Lower Temperature ◽  
Molecular Libraries

Abstract7-Allylindolines are valuable synthons for designing biologically active molecular libraries. Lewis acid catalyzed amino-Claisen rearrangement provides a one pot synthetic entry to these heteroarenes. In this context, Zinc chloride (ZnCl2)–N,N-dimethylformamide system efficiently catalyzed amino-Claisen rearrangements of 1-N-allylindolines to 7-allylindolines. The rearrangement is influenced by stereoelectronic effects of substituents present in 1-N-allylindolines. The substrates containing electron donating functionalities underwent rearrangement at lower temperature than substrates with electron withdrawing functional groups. The regioselectivity of the process is governed by the substitution pattern on allyl moiety in 1-N-allylindoline as well as ZnCl2 catalyst loading in the reaction system.

scholarly journals One Pot Use of Combilipases for Full Modification of Oils and Fats: Multifunctional and Heterogeneous Substrates

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 605 ◽  
Author(s):  
Sara Arana-Peña ◽  
Diego Carballares ◽  
Ángel Berenguer-Murcia ◽  
Andrés R. Alcántara ◽  
Rafael C. Rodrigues ◽  
...  
Keyword(s):  
High Specificity ◽  
Reaction Rates ◽  
Cascade Reactions ◽  
Enzyme Specificity ◽  
Case Scenario ◽  
One Pot ◽  
Worst Case ◽  
Intermediate Products ◽  
Global Reaction ◽  
Hydrolysis Of

Lipases are among the most utilized enzymes in biocatalysis. In many instances, the main reason for their use is their high specificity or selectivity. However, when full modification of a multifunctional and heterogeneous substrate is pursued, enzyme selectivity and specificity become a problem. This is the case of hydrolysis of oils and fats to produce free fatty acids or their alcoholysis to produce biodiesel, which can be considered cascade reactions. In these cases, to the original heterogeneity of the substrate, the presence of intermediate products, such as diglycerides or monoglycerides, can be an additional drawback. Using these heterogeneous substrates, enzyme specificity can promote that some substrates (initial substrates or intermediate products) may not be recognized as such (in the worst case scenario they may be acting as inhibitors) by the enzyme, causing yields and reaction rates to drop. To solve this situation, a mixture of lipases with different specificity, selectivity and differently affected by the reaction conditions can offer much better results than the use of a single lipase exhibiting a very high initial activity or even the best global reaction course. This mixture of lipases from different sources has been called “combilipases” and is becoming increasingly popular. They include the use of liquid lipase formulations or immobilized lipases. In some instances, the lipases have been coimmobilized. Some discussion is offered regarding the problems that this coimmobilization may give rise to, and some strategies to solve some of these problems are proposed. The use of combilipases in the future may be extended to other processes and enzymes.

Color Tuning of Biomass-Derived Carbon Nanodots by Reaction Temperature Toward White Light-Emitting Diodes

NANO ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. 2050159
Author(s):  
Yi Gong ◽  
Yanbing Han ◽  
Fang Zhang ◽  
Mingyue Zhai ◽  
Xing Chen ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
White Light ◽  
Heating Temperature ◽  
Light Emitting Diode ◽  
Peak Position ◽  
Carbon Nanodots ◽  
One Pot ◽  
Light Emitting ◽  
White Leds ◽  
Band Emission

In this work, carbon nanodots (CNDs) were synthesized from extract of mango leaves. Sphere nanodots were formed rapidly by one-step microwave heating. The photoluminescence (PL) of the CNDs was found greatly dependent on the reaction temperature. The emission peak position of the CNDs changed from 550[Formula: see text]nm to 430[Formula: see text]nm when the heating temperature increased from 120[Formula: see text]C to 150[Formula: see text]C. Particularly, the CNDs synthesized at 130[Formula: see text]C showed multi-band emission at 411[Formula: see text]nm, 480[Formula: see text]nm and 530[Formula: see text]nm, providing emitting color from blue to yellow. Moreover, the free chlorophyll molecules in the solution added red fluorescence at 670[Formula: see text]nm, and the integrated emitting color of the CNDs solution was close to white. Coated on a commercial 365[Formula: see text]nm light-emitting diode (LED) chip, the CNDs showed greenish white light with CIE coordinates of (0.37, 0.44). This work provided a one-pot, rapid and green method to obtain multi-emissive CNDs toward white LEDs.

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