scholarly journals Linking Chemical Reaction Intermediates of the Click Reaction to Their Molecular Diffusivity

2021 ◽  
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Click Reaction ◽  
Activation Barrier ◽  
Copper Catalyst ◽  
Enzymatic Reactions ◽  
Reaction Intermediates ◽  
Elementary Reactions ◽  
Molecular Diffusivity ◽  
Catalyst Complex ◽  
Pfg Nmr

Bipolar reactions have been provoked by reports of boosted diffusion during chemical and enzymatic reactions. To some, it is intuitively reasonable that relaxation to truly Brownian motion after passing an activation barrier can be slow, but to others the notion is so intuitively unphysical that they suspect the supporting experiments to be artifact. Here we study a chemical reaction according to whose mechanism some intermediate species should speed up while others slow down in predictable ways, if the boosted diffusion interpretation holds. Experimental artifacts would do not know organic chemistry mechanism, however. Accordingly, we scrutinize the absolute diffusion coefficient (D) during intermediate stages of the CuAAC reaction (coppercatalyzed azide-alkyne cycloaddition click reaction), using proton pulsed field-gradient nuclear magnetic resonance (PFG-NMR) to discriminate between the diffusion of various reaction intermediates. For the azide reactant, its D increases during reaction, peaks at the same time as peak reaction rate, then returns to its initial value. For the alkyne reagent, its D decreases consistent with presence of the intermediate large complexes formed from copper catalyst and its ligand, except for the 2Cu-alk complex whose more rapid D may signify that this species is the real reactive complex. For the product of this reaction, its D increases slowly as it detaches from the triazolide catalyst complex. These examples of enhanced diffusion for some molecular species and depressed diffusion for others causes us to conclude that diffusion coefficients during these elementary reactions are influenced by two components: hydrodynamic radius increase from complex formation, which slows diffusion, and energy release rate during the chemical reaction, which speeds it up. We discuss possible mechanisms and highlight that too little is yet understood about slow solvent reorganization during chemical reactions.<br>

scholarly journals Linking Chemical Reaction Intermediates of the Click Reaction to Their Molecular Diffusivity

2021 ◽  
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Click Reaction ◽  
Activation Barrier ◽  
Copper Catalyst ◽  
Enzymatic Reactions ◽  
Reaction Intermediates ◽  
Elementary Reactions ◽  
Molecular Diffusivity ◽  
Catalyst Complex ◽  
Pfg Nmr

Bipolar reactions have been provoked by reports of boosted diffusion during chemical and enzymatic reactions. To some, it is intuitively reasonable that relaxation to truly Brownian motion after passing an activation barrier can be slow, but to others the notion is so intuitively unphysical that they suspect the supporting experiments to be artifact. Here we study a chemical reaction according to whose mechanism some intermediate species should speed up while others slow down in predictable ways, if the boosted diffusion interpretation holds. Experimental artifacts would do not know organic chemistry mechanism, however. Accordingly, we scrutinize the absolute diffusion coefficient (D) during intermediate stages of the CuAAC reaction (coppercatalyzed azide-alkyne cycloaddition click reaction), using proton pulsed field-gradient nuclear magnetic resonance (PFG-NMR) to discriminate between the diffusion of various reaction intermediates. For the azide reactant, its D increases during reaction, peaks at the same time as peak reaction rate, then returns to its initial value. For the alkyne reagent, its D decreases consistent with presence of the intermediate large complexes formed from copper catalyst and its ligand, except for the 2Cu-alk complex whose more rapid D may signify that this species is the real reactive complex. For the product of this reaction, its D increases slowly as it detaches from the triazolide catalyst complex. These examples of enhanced diffusion for some molecular species and depressed diffusion for others causes us to conclude that diffusion coefficients during these elementary reactions are influenced by two components: hydrodynamic radius increase from complex formation, which slows diffusion, and energy release rate during the chemical reaction, which speeds it up. We discuss possible mechanisms and highlight that too little is yet understood about slow solvent reorganization during chemical reactions.<br>

Molecules, the Ultimate Nanomotor: Linking Chemical Reaction Intermediates to their Molecular Diffusivity

ACS Nano ◽  
2021 ◽  
Vol 15 (9) ◽  
pp. 14947-14953
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Reaction Intermediates ◽  
Molecular Diffusivity

scholarly journals Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

2011 ◽  
Vol 7 ◽  
pp. 1421-1435 ◽  
Author(s):  
Lukas Hintermann ◽  
Mauro Perseghini ◽  
Antonio Togni
Keyword(s):  
Asymmetric Catalysis ◽  
Lewis Acids ◽  
Enantiomeric Excess ◽  
Acetonitrile Solution ◽  
Reaction Intermediates ◽  
Reaction Parameters ◽  
Dichloromethane Solution ◽  
Ligand Structure ◽  
Catalyst Complex ◽  
Experimental Findings

Titanium-based Lewis acids catalyze the α-fluorination of β-ketoesters by electrophilic N–F-fluorinating reagents. Asymmetric catalysis with TADDOLato–titanium(IV) dichloride (TADDOL = α,α,α',α'-tetraaryl-(1,3-dioxolane-4,5-diyl)-dimethanol) Lewis acids produces enantiomerically enriched α-fluorinated β-ketoesters in up to 91% enantiomeric excess, with either F–TEDA (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)) in acetonitrile solution or NFSI (N-fluorobenzenesulfonimide) in dichloromethane solution as fluorinating reagents. The effects of various reaction parameters and of the TADDOL ligand structure on the catalytic activity and enantioselectivity were investigated. The absolute configuration of several fluorination products was assigned through correlation. Evidence for ionization of the catalyst complex by chloride dissociation, followed by generation of titanium β-ketoenolates as key reaction intermediates, was obtained. Based on the experimental findings, a general mechanistic sketch and a steric model of induction are proposed.

Chemical Reaction Kinetics in Solution

2004 ◽  
Author(s):  
W. Ronald Fawcett
Keyword(s):  
Reaction Kinetics ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Physical Property ◽  
Theoretical Description ◽  
Time Range ◽  
Chemical Changes ◽  
Elementary Reactions ◽  
Chemical Reaction Kinetics ◽  
Liquid Solutions

The kinetics of chemical reactions were first studied in liquid solutions. These experiments involved mixing two liquids and following the change in the concentration of a reactant or product with time. The concentration was monitored by removing a small sample of the solution and stopping the reaction, for example, by rapidly lowering the temperature, or by following a physical property of the system in situ, for example, its color. Although the experiments were initially limited to slow reactions, they established the basic laws governing the rate at which chemical changes occur. The variables considered included the concentrations of the reactants and of the products, the temperature, and the pressure. Thus, the reacting system was examined using the variables normally considered for a system at equilibrium. Most reactions were found to be complex, that is, to be made up of several elementary steps which involved one or two reactants. As the fundamental concepts of chemical kinetics developed, there was a strong interest in studying chemical reactions in the gas phase. At low pressures the reacting molecules in a gaseous solution are far from one another, and the theoretical description of equilibrium thermodynamic properties was well developed. Thus, the kinetic theory of gases and collision processes was applied first to construct a model for chemical reaction kinetics. This was followed by transition state theory and a more detailed understanding of elementary reactions on the basis of quantum mechanics. Eventually, these concepts were applied to reactions in liquid solutions with consideration of the role of the non-reacting medium, that is, the solvent. An important turning point in reaction kinetics was the development of experimental techniques for studying fast reactions in solution. The first of these was based on flow techniques and extended the time range over which chemical changes could be observed from a few seconds down to a few milliseconds. This was followed by the development of a variety of relaxation techniques, including the temperature jump, pressure jump, and electrical field jump methods. In this way, the time for experimental observation was extended below the nanosecond range.

Separation of Chemical Reaction Intermediates by Metal-Organic Frameworks

Small ◽  
2011 ◽  
Vol 7 (16) ◽  
pp. 2356-2364 ◽  
Author(s):  
Andrea Centrone ◽  
Erik E. Santiso ◽  
T. Alan Hatton
Keyword(s):  
Chemical Reaction ◽  
Metal Organic Frameworks ◽  
Reaction Intermediates ◽  
Metal Organic

scholarly journals PENGGUNAAN TEMBAGA SEBAGAI BAHAN CATALYTIC CONVERTER TERHADAP PERFORMA MESIN SEPEDA MOTOR SATRIA FU 150

2018 ◽  
Vol 3 (2) ◽  
pp. 97-106
Author(s):  
Muhammad Zaki ◽  
Abdul Ghofur ◽  
Sigit Mujiarto
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Chemical Reaction ◽  
Catalytic Converter ◽  
Copper Catalyst ◽  
Engine Performance ◽  
Copper Plate

Many motorcycles  increased  within past few years, the gas emmited from the motorclyce will be polluted  the population. One of technology that can reduce the emmited gas is using catalytic converter on the muffler. Catalytic converter is a catalyst that can alter or accelerate a matter (chemical reaction) of a carbon monoxide into carbon dioxide. In this research will use two types of catalytic converter that is honey comb and a copper plate. From the test can be seen that the catalytic converter with a honey comb shape better in terms of engine performance than the catalytic converter shaped plate. Compared wihtout any catalytic converter, the highest percentage honey comb catalyst reduce  the power within 0.12 HP, and torque increased to 0.04 Nm. While the highest copper catalyst  that reduce the power within 0.71 HP, and torque decreased to 0.2 Nm.

scholarly journals Particle-based simulation reveals macromolecular crowding effects on the Michaelis-Menten mechanism

2018 ◽  
Author(s):  
Daniel R. Weilandt ◽  
Vassily Hatzimanikatis
Keyword(s):  
Computational Models ◽  
Enzyme Reaction ◽  
Phosphoglycerate Mutase ◽  
Cell Physiology ◽  
Enzymatic Reactions ◽  
Elementary Reactions ◽  
Elementary Kinetics ◽  
Kinetics Of

AbstractMany computational models for analyzing and predicting cell physiology rely onin vitrodata, collected in dilute and cleanly controlled buffer solutions. However, this can mislead models because about 40% of the intracellular volume is occupied by a dense mixture of proteins, lipids, polysaccharides, RNA, and DNA. These intracellular macromolecules interact with enzymes and their reactants and affect the kinetics of biochemical reactions, makingin vivoreactions considerably more complex than thein vitrodata indicates. In this work, we present a new type of kinetics that captures and quantifies the effect of volume exclusion and any other spatial phenomena on the kinetics of elementary reactions. We further developed a framework that allows for the efficient parameterization of this type of kinetics using particle simulations. Our formulation, entitled GEneralized Elementary Kinetics (GEEK), can be used to analyze and predict the effect of intracellular crowding on enzymatic reactions and was herein applied to investigate the influence of crowding on phosphoglycerate mutase inEscherichia coli, which exhibits prototypical reversible Michaelis-Menten kinetics. Current research indicates that many enzymes are reaction limited and not diffusion limited, and our results suggest that the influence of fractal diffusion is minimal for these reaction-limited enzymes. Instead, increased association rates and decreased dissociation rates lead to a strong decrease in the effective maximal velocitiesVmaxand the effective Michaelis-Menten constantsKMunder physiologically relevant volume occupancies. Finally, the effects of crowding in the context of a linear pathway were explored, with the finding that crowding can have a redistributing effect, relative to ideal conditions, on the effective flux responses in the case of two-fold enzyme overexpression. We suggest that the presented framework in combination with detailed kinetics models will improve our understanding of enzyme reaction networks under non-ideal conditions.

scholarly journals Effect of Thermal Radiation, Chemical Reaction and Viscous Dissipation on MHD Flow

2018 ◽  
Vol 23 (3) ◽  
pp. 787-801
Author(s):  
B. Zigta
Keyword(s):  
Kinetic Energy ◽  
Differential Equations ◽  
Thermal Radiation ◽  
Viscous Dissipation ◽  
Chemical Reaction ◽  
Energy Equation ◽  
Eckert Number ◽  
Radiation Chemical ◽  
Thermal Buoyancy ◽  
Molecular Diffusivity

Abstract This study examines the effect of thermal radiation, chemical reaction and viscous dissipation on a magnetohydro- dynamic flow in between a pair of infinite vertical Couette channel walls. The momentum equation accounts the effects of both the thermal and the concentration buoyancy forces of the flow. The energy equation addresses the effects of the thermal radiation and viscous dissipation of the flow. Also, the concentration equation includes the effects of molecular diffusivity and chemical reaction parameters. The gray colored fluid considered in this study is a non-scattering medium and has the property of absorbing and emitting radiation. The Roseland approximation is used to describe the radiative heat flux in the energy equation. The velocity of flow transforms kinetic energy into heat energy. The increment of the velocity due to internal energy results in heating up of the fluid and consequently it causes increment of the thermal buoyancy force. The Eckert number being the ratio of the kinetic energy of the flow to the temperature difference of the channel walls is directly proportional to the thermal energy dissipation. It can be observed that increasing the Eckert number results in increasing velocity. A uniform magnetic field is applied perpendicular to the channel walls. The temperature of the moving wall is high enough due to the presence of thermal radiation. The solution of the governing equations is obtained using regular perturbation techniques. These techniques help to convert partial differential equations to a set of ordinary differential equations in dimensionless form and thus they are solved analytically. The following results are obtained: from the simulation study it is observed that the flow pattern of the fluid is affected due to the influence of the thermal radiation, the chemical reaction and viscous dissipation. The increment in the Hartmann number results in the increment of the Lorentz force but a decrement in velocity of the flow. An increment in the radiative parameter results in a decrement in temperature. An increment in the Prandtl number results in a decrement in thermal diffusivity. An increment in both the chemical reaction parameter and molecular diffusivity results in a decrement in concentration.

scholarly journals Effect of heat source and chemical reaction on MHD flow past a vertical plate with variable temperature

2016 ◽  
Vol 13 (1) ◽  
pp. 101-110 ◽  
Author(s):  
P. K. Rout ◽  
S. N. Sahoo ◽  
G. C. Dash
Keyword(s):  
Heat Source ◽  
Chemical Reaction ◽  
Vertical Plate ◽  
Variable Temperature ◽  
Mhd Flow ◽  
Governing Equations ◽  
Molecular Diffusivity ◽  
Flow Parameters ◽  
Flow Past ◽  
Chemical Reaction Parameter

An analysis has been carried out to study the effect of heat source and chemical reaction on MHD flow past a vertical plate subject to a constant motion with variable temperature and concentration. The governing equations are solved by the Laplace transformation technique. The effects of various flow parameters on the flow dynamics are discussed. Findings of the present study reveal that the velocity of the fluid reduces due to the dominating effect of kinematic viscosity over molecular diffusivity in case of heavier species. Presence of heat source reduces the velocity of the flow. Presence of chemical reaction parameter decreases the concentration distribution.

scholarly journals Enzymatic preparation of functional polysaccharide hydrogels by phosphorylase catalysis

2018 ◽  
Vol 90 (6) ◽  
pp. 1045-1054 ◽  
Author(s):  
Jun-ichi Kadokawa
Keyword(s):  
Glutamic Acid ◽  
Chemical Reaction ◽  
Carboxymethyl Cellulose ◽  
Room Temperature ◽  
Polymeric Materials ◽  
Enzymatic Polymerization ◽  
Enzymatic Reactions ◽  
Enzymatic Preparation ◽  
Ph Responsive ◽  
Chitin Nanofiber

Abstract This article reviews enzymatic preparation of functional polysaccharide hydrogels by means of phosphorylase-catalyzed enzymatic polymerization. A first topic of this review deals with the synthesis of amylose-grafted polymeric materials and their formation of hydrogels, composed of abundant natural polymeric main-chains, such as chitosan, cellulose, xantham gum, carboxymethyl cellulose, and poly(γ-glutamic acid). Such synthesis was achieved by combining the phosphorylase-catalyzed enzymatic polymerization forming amylose with the appropriate chemical reaction (chemoenzymatic method). An amylose-grafted chitin nanofiber hyrogel was also prepared by the chemoenzymatic approach. As a second topic, the preparation of glycogen hydrogels by the phosphorylase-catalyzed enzymatic reactions was described. When the phosphorylase-catalyzed enzymatic polymerization from glycogen as a polymeric primer was carried out, followed by standing the reaction mixture at room temperature, a hydrogel was obtained. pH-Responsive amphoteric glycogen hydrogels were also fabricated by means of the successive phosphorylase-catalyzed enzymatic reactions.

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