Inverse solvent effects in the heterogeneous and homogeneous epoxidation of cis-2-heptene with [2-percarboxyethyl]-functionalized silica and meta-chloroperbenzoic acid

2014 ◽  
Vol 12 (20) ◽  
pp. 3246-3250 ◽  
Author(s):  
Rossella Mello ◽  
Jeymy T. Sarmiento-Monsalve ◽  
Diana Vargas-Oviedo ◽  
Rafael Acerete ◽  
María Elena González-Núñez ◽  
...  
Keyword(s):  
Solid Surface ◽  
Solvent Effects ◽  
Reaction Rate ◽  
Functionalized Silica ◽  
Solvent Layer

The organized solvent layer on the solid surface determines the reaction rate in the heterogeneous epoxidation of cis-2-heptene.

scholarly journals Methyl Iodide Adsorption on Reduced Silver-Functionalized Silica Aerogel: How Temperature Impacts the Adsorption?

2021 ◽  
Author(s):  
Siqi Tang ◽  
Seungrag Choi ◽  
Lawrence Tavlarides
Keyword(s):  
Methyl Iodide ◽  
Photoelectron Spectroscopy ◽  
Silica Aerogel ◽  
Reaction Rate ◽  
Reaction Pathway ◽  
Effect Of Temperature ◽  
Functionalized Silica ◽  
Contributing Factors ◽  
X Ray ◽  
Temperature Impacts

To understand the effect of temperature to the adsorption, 104 ppbv and 1044 ppbv methyl iodide (CHI) adsorptions on reduced silver-functionalized silica aerogel (Ag-Aerogel) at 100, 150 and 200 ℃ were performed. In the experiments, a significantly high uptake rate (3 – 4 times higher than that at 100 and 150 ℃) was observed for the 104 ppbv adsorption at 200 ℃. To explain such behavior, a potential reaction pathway was proposed and multiple physical analyses including nitrogen titration, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. Based on the results, the contributing factors appear to be the formation of different Ag-I components induced by temperature, higher silver site availability, decreasing diffusion limitation, and increasing reaction rate described by the Arrhenius relationship.

Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis

2018 ◽  
Vol 20 (16) ◽  
pp. 11317-11326 ◽  
Author(s):  
A. Wangler ◽  
R. Canales ◽  
C. Held ◽  
T. Q. Luong ◽  
R. Winter ◽  
...  
Keyword(s):  
Equilibrium Constant ◽  
Solvent Effects ◽  
Reaction Rate ◽  
Peptide Hydrolysis ◽  
Michaelis Constant ◽  
Thermodynamic Activities ◽  
Reaction Equilibrium

This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant Kth of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations.

Intermolecular perturbation approach to specific solvent effects

1985 ◽  
Vol 63 (7) ◽  
pp. 1382-1385 ◽  
Author(s):  
Ottó B. Nagy
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Solvent Effect ◽  
Solvent Effects ◽  
Reaction Rate ◽  
Order Perturbation ◽  
Order Perturbation Theory ◽  
Perturbation Approach ◽  
Donor Ability ◽  
Second Order Perturbation Theory

One possible specific solvent effect, namely, the π-donor ability is considered in the light of simple intermolecular second order perturbation theory. By using the Polányi–Evans–Bell principle this theory predicts that increasing -π-donor ability of solvent should decrease the reaction rate. This prediction is fully borne out by experimental data observed for the solvent effect on 4 + 2 cycloaddition of tétracyanoethylène to anthracene.

Shear induced formation of lubrication layers of negative normal stress gels

Soft Matter ◽  
2017 ◽  
Vol 13 (37) ◽  
pp. 6515-6520 ◽  
Author(s):  
Tetsuya Yamamoto ◽  
Yuichi Masubuchi ◽  
Masao Doi
Keyword(s):  
Normal Stress ◽  
Solid Surface ◽  
Polymer Networks ◽  
Contact Friction ◽  
Biopolymer Gels ◽  
Solvent Layer

Many biopolymer gels generate negative normal stress, with which their polymer networks shrink in the normal of applied shear. Shearing such a gel produces a solvent layer, which greatly reduces the contact friction between the gel and the solid surface.

Solvent Effects on the Kinetics and Mechanism of the Acid-Catalysed Hydrolysis of Diterf.-butylsuccinate in Dioxane-Water Mixtures

1985 ◽  
Vol 40 (1) ◽  
pp. 84-91 ◽  
Author(s):  
Adel N. Asaad ◽  
Fayez Y. Khalil
Keyword(s):  
Dielectric Constant ◽  
Solvent Effects ◽  
Rate Constants ◽  
Mixed Type ◽  
Reaction Rate ◽  
Solvent Composition ◽  
Water Molecules ◽  
Molecular Dipole ◽  
First Order ◽  
Hydrolysis Of

The acid-catalysed hydrolysis of ditert.-butylsuccinate in dioxane-water mixtures proceeds via consecutive first-order reactions. The rate constants kI and kII corresponding to the two steps decrease with increasing dioxane content of the medium. After reaching a minimum at 90% (w/w) dioxane, both rate constants increase again with further addition of dioxane. The kinetic ratio kI/kII is smaller than the statistical value 2.0, and is markedly affected both by solvent composition and temperature. The maximum concentration of the intermediate half ester decreases with increasing dioxane content. The observed activation energies EI and EII of the two steps of the reaction are largely dependent on temperature as well as solvent composition indicating a mixed type of bond fission represented by the AAl 1 and AAC 2 mechanisms, whose relative contributions in the overall rate constants kI and kIIcould be calculated on the basis of the number of water molecules incorporated in the corresponding transition states. The effect of bulk dielectric constant on the reaction rate was investigated in the light of the available electrostatic theories and showed the reaction to be an ion-molecular dipole type of interaction. The activation thermodynamic parameters were computed and discussed as criteria of solvent effect and mechanism.

Optimization of Chemical Reaction Processes in Microreactors Using Reaction Rate Analyses

2011 ◽  
Author(s):  
Yukako Asano ◽  
Shigenori Togashi ◽  
Yoshishige Endo
Keyword(s):  
Reaction Time ◽  
Quantum Chemical Calculations ◽  
Solvent Effects ◽  
Quantum Chemical ◽  
Reaction Rate ◽  
Side Reaction ◽  
Reaction Rates ◽  
Sandmeyer Reaction ◽  
Diffusion Controlled ◽  
Bromination Reaction

We applied microreactors to the three following reactions: a consecutive bromination reaction, the two-step Sandmeyer reaction, and an acetylation reaction including solvent effects. We obtained the reaction rate constants from few experimental data or quantum chemical calculations and optimized the reaction conditions such as the reaction times and temperature. We then experimentally validated them by microreactors. A consecutive bromination reaction, where the objective reaction was followed by the side reaction, was one of the processes. The reaction temperature played an important role in the effects of a microreactor. The yield of the objective product was improved by about 40% using a microreactor. The two-step Sandmeyer reaction was also applied, where the 1st-step reaction was followed by the 2nd-step reaction to produce the objective product. The 1st-step reaction had the diffusion-controlled process, while the 2nd-step reaction had the reaction-controlled one. The yield of the objective product was improved when microreactors were used and the reaction time for the 2nd-step reaction was set appropriately. Moreover, an acetylation reaction including solvent effects on reaction rates was considered and the solvent effects could be predicted from quantum chemical calculations. The calculation suggested that acetic acid with the larger electron-accepting property gave more stability to the species formed in the transition state. The reaction time was shortened using a microreactor, when the reaction process was changed from reaction-controlled to diffusion-controlled by changing the solvent used.

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