Insight into the electronic effect of phosphine ligand on Rh catalyzed CO2 hydrogenation by investigating the reaction mechanism

2016 ◽  
Vol 18 (6) ◽  
pp. 4860-4870 ◽  
Author(s):  
Shao-Fei Ni ◽  
Li Dang
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Coordination Sphere ◽  
Metal Hydride ◽  
Electronic Effect ◽  
Catalytic Efficiency ◽  
Co2 Hydrogenation ◽  
Diphosphine Ligand ◽  
Rate Determining Step ◽  
Insight Into

The effect of the outer coordination sphere of the diphosphine ligand on the catalytic efficiency of [Rh(PCH2XRCH2P)2]+ (XR = CH2, N–CH3, CF2) catalyzed CO2 hydrogenation was studied. It was found that the hydricity of the metal hydride bond determined the activation energy of the rate determining step of the reaction.

scholarly journals Mechanistic Insights into Water-Catalyzed Formation of Levoglucosenone from Anhydrosugar Intermediates by Means of High-Level Theoretical Procedures

2016 ◽  
Vol 69 (9) ◽  
pp. 943 ◽  
Author(s):  
Wenchao Wan ◽  
Li-Juan Yu ◽  
Amir Karton
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Ring Opening ◽  
Reaction Pathway ◽  
Fast Pyrolysis ◽  
Rate Determining Step ◽  
Dehydration Reactions ◽  
High Level ◽  
Multistep Reaction ◽  
Hydration And Dehydration

Levoglucosenone (LGO) is an important anhydrosugar product of fast pyrolysis of cellulose and biomass. We use the high-level G4(MP2) thermochemical protocol to study the reaction mechanism for the formation of LGO from the 1,4:3,6-dianhydro-α-d-glucopyranose (DGP) pyrolysis intermediate. We find that the DGP-to-LGO conversion proceeds via a multistep reaction mechanism, which involves ring-opening, ring-closing, enol-to-keto tautomerization, hydration, and dehydration reactions. The rate-determining step for the uncatalyzed process is the enol-to-keto tautomerization (ΔG‡298 = 68.6 kcal mol–1). We find that a water molecule can catalyze five of the seven steps in the reaction pathway. In the water-catalyzed process, the barrier for the enol-to-keto tautomerization is reduced by as much as 15.1 kcal mol–1, and the hydration step becomes the rate-determining step with an activation energy of ΔG‡298 = 58.1 kcal mol–1.

Mechanism of C–P bond formation via Pd-catalyzed decarbonylative phosphorylation of amides: insight into the chemistry of the second coordination sphere

2020 ◽  
Vol 56 (1) ◽  
pp. 113-116
Author(s):  
Wen-Yan Tong ◽  
Thu D. Ly ◽  
Tao-Tao Zhao ◽  
Yan-Bo Wu ◽  
Xiaotai Wang
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Coordination Sphere ◽  
Bond Formation ◽  
Dft Computations ◽  
Detailed Reaction Mechanism ◽  
Non Covalent Interactions ◽  
Second Coordination Sphere ◽  
Covalent Interactions ◽  
Insight Into

DFT computations establish a detailed reaction mechanism for the first Pd-catalyzed decarbonylative phosphorylation of amides forming C–P bonds, which includes non-covalent interactions as well as proton transfer in the second coordination sphere.

6. Changing the identity of matter

2014 ◽  
pp. 86-105
Author(s):  
Peter Atkins
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Equilibrium Constant ◽  
Chemical Kinetics ◽  
Chemical Reactions ◽  
Chemical Dynamics ◽  
Rate Determining Step ◽  
Constant Rate ◽  
Key Terms ◽  
Spontaneous Reaction

A great deal of chemistry is concerned with changing the identity of matter by the deployment of chemical reactions. Physical chemists are interested in a variety of aspects of chemical reactions, including the rates at which they take place (chemical kinetics) and the details of the steps involved during the transformation (chemical dynamics). Chemical reactions can be achieved simply by mixing and heating, but some are stimulated by light (photochemistry) and others by electricity (electrochemistry). ‘Changing the identity of matter’ explains the key terms of chemical kinetics and chemical dynamics such as spontaneous reaction, reaction quotient, equilibrium constant, rate law, reaction mechanism, rate-determining step, activation energy, and catalysis.

scholarly journals Mechanistic insight into propane dehydrogenation into propylene over chromium (III) oxide by cluster approach and Density Functional Theory calculations

2020 ◽  
Vol 11 (4) ◽  
pp. 342-350
Author(s):  
Toyese Oyegoke ◽  
Fadimatu Nyako Dabai ◽  
Adamu Uzairu ◽  
Baba El-Yakubu Jibril
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Reaction Pathway ◽  
Hydrogen Abstraction ◽  
Propane Dehydrogenation ◽  
Propane Conversion ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Insight Into

A preliminary study to provides insight into the kinetic and thermodynamic assessment of the reaction mechanism involved in the non-oxidative dehydrogenation (NOD) of propane to propylene over Cr2O3, using a density functional theory (DFT) approach, has been undertaken. The result obtained from the study presents the number of steps involved in the reaction and their thermodynamic conditions across different routes. The rate-determining step (RDS) and a feasible reaction pathway to promote propylene production were also identified. The results obtained from the study of the 6-steps reaction mechanism for dehydrogenation of propane into propylene identified the first hydrogen abstraction and hydrogen desorption to be endothermic. In contrast, other steps that include propane’s adsorption, hydrogen diffusion, and the second stage of hydrogen abstraction were identified as exothermic. The study of different reaction routes presented in the energy profiles confirms the Cr-O (S1, that is, the reaction pathway that activates the propane across the Cr-O site at the alpha or the terminal carbon of the propane) pathway to be the thermodynamically feasible pathway for the production of propylene. The first hydrogen abstraction step was identified as the potential rate-determining step for defining the rate of the propane dehydrogenation process. This study also unveils that the significant participation of Cr sites in the propane dehydrogenation process and how the Cr high surface concentration would hinder the desorption of propylene and thereby promote the production of undesired products due to the stronger affinity that exists between the propylene and Cr-Cr site, which makes it more stable on the surface. These findings thereby result in Cr-site substitution suggestion to prevent deep dehydrogenation in propane conversion to propylene. This insight would aid in improving the catalyst performance.

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

Full Kinetics and a Mechanism Investigation for the Generation of 4- Substituted 1, 4-Dihydropyridine Derivatives in the Presence of Green Catalyst and Aqueous Medium: Experimental Procedure

2020 ◽  
Vol 17 ◽  
Author(s):  
Sayyed Mostafa Habibi-Khorassani ◽  
Mehdi Shahraki ◽  
Sadegh Talaiefar
Keyword(s):  
Reaction Mechanism ◽  
Reaction Centre ◽  
Green Catalyst ◽  
Experimental Procedure ◽  
Dominant Mechanism ◽  
Rate Determining Step ◽  
12 Steps ◽  
Reaction Constant ◽  
Substituted 1 ◽  
Dihydropyridine Derivatives

Aims and Objective: The main objective of the kinetic investigation of the reaction among ethyl acetoacetate 1, ammoniumacetat 2, dimedone 3 and diverse substitutions of benzaldehyde 4-X, (X= H, NO2, CN, CF3, Cl, CH (CH3)2, CH3, OCH3, OCH3, and OH) for the generation of 4-substituted 1, 4-dihydropyridine derivatives (product 5) was the recognition of the most realistic reaction mechanism. The layout of the reaction mechanism studied kinetically by means of the UV-visible spectrophotometry approach. Materials and Methods: Among the various mechanisms, only mechanism1 (path1) involving 12 steps was recognized as a dominant mechanism (path1). Herein, the reaction between reactants 1 and 2 (kobs= 814.04 M-1 .min-1 ) and also compound 3 and 4-H (kobs= 151.18 M-1 .min-1 ) were the logical possibilities for the first and second fast steps (step1 and step2, respectively). Amongst the remaining steps, only step9 of the dominant mechanism (path1) had substituent groups (X) near the reaction centre that could be directly resonated with it. Results and Discussion: Para electron-withdrawing or donating groups on the compound 4-X increases the rate of the reaction 4 times more or decreases 8.7 times less than the benzaldehyde alone. So, this step is sensitive for monitoring any small or huge changes in the reaction rate. For this reason, step9 is the rate-determining step of the reaction mechanism (path1). Conclusion: The recent result is the agreement with the Hammett description with an excellent dual substituent factor (r = 0.990) and positive value of reaction constant (ρ = +0.9502) which confirmed both the resonance and inductive effects “altogether” contributed on the reaction centre of step9 in the dominant mechanism (path1).

Gas Cell Infrared and Attenuated Total Reflection Infrared Spectroscopic Studies for Organic–Inorganic Interactions in Adsorption of Fulvic Acid on the Goethite Surface Generating Carbon Dioxide

2021 ◽  
pp. 000370282199121
Author(s):  
Yuki Nakaya ◽  
Satoru Nakashima ◽  
Takahiro Otsuka
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Fulvic Acid ◽  
Spectroscopic Studies ◽  
Reaction Model ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Gas Cell ◽  
Rate Determining Step ◽  
Ir Spectroscopic

The generation of carbon dioxide (CO2) from Nordic fulvic acid (FA) solution in the presence of goethite (α-FeOOH) was observed in FA–goethite interaction experiments at 25–80 ℃. CO2 generation processes observed by gas cell infrared (IR) spectroscopy indicated two steps: the zeroth order slower CO2 generation from FA solution commonly occurring in the heating experiments of the FA in the presence and absence of goethite (activation energy: 16–19 kJ mol–1), and the first order faster CO2 generation from FA solution with goethite (activation energy: 14 kJ mol–1). This CO2 generation from FA is possibly related to redox reactions between FA and goethite. In situ attenuated total reflection infrared (ATR-IR) spectroscopic measurements indicated rapid increases with time in IR bands due to COOH and COO– of FA on the goethite surface. These are considered to be due to adsorption of FA on the goethite surface possibly driven by electrostatic attraction between the positively charged goethite surface and negatively charged deprotonated carboxylates (COO–) in FA. Changes in concentration of the FA adsorbed on the goethite surface were well reproduced by the second order reaction model giving an activation energy around 13 kJ mol–1. This process was faster than the CO2 generation and was not its rate-determining step. The CO2 generation from FA solution with goethite is faster than the experimental thermal decoloration of stable structures of Nordic FA in our previous report possibly due to partial degradations of redox-sensitive labile structures in FA.

CO2 hydrogenation on a metal hydride surface

2012 ◽  
Vol 14 (16) ◽  
pp. 5518 ◽  
Author(s):  
Shunsuke Kato ◽  
Andreas Borgschulte ◽  
Davide Ferri ◽  
Michael Bielmann ◽  
Jean-Claude Crivello ◽  
...  
Keyword(s):  
Metal Hydride ◽  
Co2 Hydrogenation
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