THEORETICAL INVESTIGATION ON THE REACTION MECHANISM OF CuI-CATALYZED FORMATION OF ETHYL 2-PHENYLACETOACETATE

2009 ◽  
Vol 08 (supp01) ◽  
pp. 1087-1098
Author(s):  
LAI-CAI LI ◽  
YING ZHANG ◽  
AN-MIN TIAN ◽  
NING-BEW WONG
Keyword(s):  
Reaction Mechanism ◽  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Catalytic Mechanism ◽  
Functional Theory ◽  
Nonlocal Correlation ◽  
Rate Determining Step ◽  
Stage 1 ◽  
Two Stages

The reaction mechanism of CuI -catalyzed formation of ethyl 2-phenylacetoacetate by arylation of ethyl acetoacetate has been investigated by density functional theory (DFT) using Becke's three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional (B3LYP). The geometries of the reactants, intermediates, transition states, and products have been optimized and verified by means of vibration frequency calculations. According to our assumption, this reaction can be divided into two stages. The rate-determining step is found to be the 3 → 4-TS procedure, which is the first procedure of stage 1. The low energy barrier of 39.85 kcal/mol indicates that this reaction can be carried out, which is in accordance with the experimental facts. For comparison, we have investigated the reaction mechanism of the same chemical reaction without CuI catalyst, whose energy barrier of rate-determining step is 212.76 kcal/mol higher than that with CuI catalyst. This fact suggests that CuI catalyst accelerates the reaction by remarkably lowering the energy barrier. The solvation effects on the barriers of the reaction are important. But the energetic order in DMSO solvent seems to be almost the same as that in gas-phase, which indicates that our conclusion achieved in gas-phase is believable. Our findings reveal the microscopic catalytic mechanism of CuI and are in agreement with the experimental facts.

Ethylenediamine Catalyzed Decarboxylation of Oxaloacetic Acid: A DFT Investigation

2013 ◽  
Vol 781-784 ◽  
pp. 253-258
Author(s):  
Ming Zhi Song ◽  
Zai Long Zhang ◽  
Chuan Gang Fan ◽  
Da Zhi Li ◽  
Shi Guo Zhang
Keyword(s):  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Water Solution ◽  
Membered Ring ◽  
Transition Structure ◽  
Functional Theory ◽  
Oxaloacetic Acid ◽  
Stepwise Mechanism ◽  
Rate Determining Step

The decarboxylation mechanism of oxaloacetic acid aided with ethylenediamine or without any catalyst is investigated employing Density Functional Theory (DFT). DFT calculations for both the gas phase and in water solution indicate a stepwise mechanism for each of the steps of the reactions. In the catalyzed mechanism, the dehydration of carbinolamine (IM1) is via a seven-membered ring transition structure (TS5), which is consistent with the structure proposed by Thalji, et al. The decarboxylation of the imine (IM6) is the rate determining step with an energy barrier of 16.46 kcal/mol, lower than the reaction without any catalysts or catalyzed with ions.

scholarly journals Ensemble Effects of Explicit Solvation on Allylic Oxidation

2021 ◽  
Author(s):  
Hung Le ◽  
Mariano Guagliardo ◽  
Anne Gorden ◽  
Aurora Clark
Keyword(s):  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Umbrella Sampling ◽  
Catalytic Cycle ◽  
Allylic Oxidation ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Ensemble Effects ◽  
Explicit Solvation

<div>Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene</div><div>using a Cu(II) (E)-6-amino-7-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile, which creates the desired cyclohexenone and H 2 O as products. In comparison to prior study using gas-phase DFT, a significant solvent effect is observed on the rate determining allylic H-atom abstraction step (which has a free energy barrier of 12.1 ± 0.2 kcal/mol). During the cycle, the explicit solvation and ensemble sampling of solvent configurations reveals an important dehydrogenation and re-hydrogenation step of the -NH 2 ligand that is essential to catalyst recovery. This work illustrates the importance of ensemble solvent configurational sampling to reveal the breadth of processes that underpin the full catalytic cycle.</div>

scholarly journals Theoretical investigation on the effect of the ligand on bis-silylation of C(sp)–C(sp) by Ni complexes

RSC Advances ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 1005-1010
Author(s):  
Li Hui ◽  
He Yuhan ◽  
Wang Jiaqi
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Transition Metal ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Active Catalyst ◽  
Organic Ligand ◽  
Organic Complex ◽  
Functional Theory ◽  
Rate Determining Step

Density functional theory (DFT) is used to study the bis-silylation of alkynes catalyzed by a transition metal nickel–organic complex; the active catalyst, the organic ligand, the reaction mechanism, and rate-determining step are discussed in this paper.

BONDING FEATURES AND REACTION MECHANISM OF THE OXIDATION OF 2-PROPANOL BY A Cp*Ir AMIDO COMPLEX

2010 ◽  
Vol 09 (supp01) ◽  
pp. 99-107
Author(s):  
LINGJUN LIU ◽  
SIWEI BI ◽  
MIN SUN ◽  
XIANGAI YUAN ◽  
PING LI
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Dft Calculations ◽  
Density Functional ◽  
Bond Distance ◽  
Mechanistic Study ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Model Complex ◽  
Membered Transition State

The mechanistic study on the oxidation of 2-propanol by the model complex CpIr [κ2-(N,C)-( NHCMe2–2-C6H4)] (R) is performed using density functional theory (DFT) calculations. It is found that the rate-determining step is the hydrogen migration from 2-propanol to R via a six-membered transition state. The reaction is calculated to be favorable thermodynamically. To further understand the reaction mechanism, some bonding features are discussed, such as the correlation of the geometry of R and the Ir–N π bond involved, the transformation of the nitrogen hybridization, the variation of Ir–N bond distance, and so on.

scholarly journals Ensemble Effects of Explicit Solvation on Allylic Oxidation

2021 ◽  
Author(s):  
Hung Le ◽  
Mariano Guagliardo ◽  
Anne Gorden ◽  
Aurora Clark
Keyword(s):  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Umbrella Sampling ◽  
Catalytic Cycle ◽  
Allylic Oxidation ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Ensemble Effects ◽  
Explicit Solvation

<div>Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene</div><div>using a Cu(II) (E)-6-amino-7-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile, which creates the desired cyclohexenone and H 2 O as products. In comparison to prior study using gas-phase DFT, a significant solvent effect is observed on the rate determining allylic H-atom abstraction step (which has a free energy barrier of 12.1 ± 0.2 kcal/mol). During the cycle, the explicit solvation and ensemble sampling of solvent configurations reveals an important dehydrogenation and re-hydrogenation step of the -NH 2 ligand that is essential to catalyst recovery. This work illustrates the importance of ensemble solvent configurational sampling to reveal the breadth of processes that underpin the full catalytic cycle.</div>

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.

Effect of Substitution for Insertion of CO2 into Epoxides and Aziridines: An Ab Initio Study

2020 ◽  
Vol 73 (1) ◽  
pp. 30
Author(s):  
Yunhan Yang ◽  
Fenji Li ◽  
Cuicui Yang ◽  
Lijuan Jia ◽  
Lijuan Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Reaction Mechanism ◽  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Concerted Mechanism

The insertion of CO2 into epoxides and aziridines has been studied using density functional theory (B3LYP) and ab initio (MP2) methods, and the effect of substitution for the two reactions are further explored. It is found that the reactivity of epoxides and aziridines are similar, and insertion of CO2 proceeds through a concerted mechanism. The substitutions of methyl and phenyl does not change the reaction mechanism, but the transition state for the substitution on the attacking position becomes loose with a lower free energy barrier. The substitutions of methyl and phenyl decrease the free energy barrier, with phenyl substitution having a greater affect. The results also show that the free energy barriers for the insertions of CO2 into aziridines are ~10kcalmol−1 lower than the corresponding reactions of CO2 with epoxides.

Theoretical Study on Aggregation of Nuclei-Containing Gas Phase

2017 ◽  
Author(s):  
Zhong Lan ◽  
Quan Xue ◽  
Xuehu Ma ◽  
Di Wang ◽  
Kejian Cao ◽  
...  
Keyword(s):  
Water Molecule ◽  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Water Clusters ◽  
Condensation Nucleus ◽  
Condensation Process ◽  
Functional Theory ◽  
Particle Properties ◽  
Molecule Aggregation

Haze is a kind of typical heterogeneous nucleation phenomenon in gas phase condensation process. The existence of dust nucleus may induce water molecule aggregation among vapor phase under a certain humidity. In this article, we try to use Density Functional Theory simulation to explore the evolution mechanism of water molecule aggregation influenced by condensation nucleus from the perspective of molecules assembling. We can get the following results: the subcooling degree and physicochemical properties of nucleation center affect the hydrogen bond within the water clusters and the transformation energy barrier of water molecule aggregation tendency. Water vapor begins to heterogeneously condense or forms aggregation humidity in a certain condition based on the center of condensation nuclei. The analysis shows that the effect law of the degree and scale of aggregation or phase transition are influenced by the change of gas phase partial pressure, supersaturated degree along with particle properties. As the energy barrier of nucleation free energy decreases, the formation of water clusters will be easier.

scholarly journals Ensemble Effects of Explicit Solvation on Allylic Oxidation

2021 ◽  
Author(s):  
Hung Le ◽  
Mariano Guagliardo ◽  
Anne Gorden ◽  
Aurora Clark
Keyword(s):  
Gas Phase ◽  
Energy Barrier ◽  
Density Functional ◽  
Umbrella Sampling ◽  
Catalytic Cycle ◽  
Allylic Oxidation ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Ensemble Effects ◽  
Explicit Solvation

Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene using a Cu(II) 7-amino-6-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile to create cyclohexenone and H$_2$O as products. In comparison to gas-phase DFT, the solvent effect is observed as the rate determining allylic H-atom abstraction step has a free energy barrier of 12.1 $\pm$ 0.2 kcal/mol in solution. During the cycle, the explicit solvation and ensemble sampling of solvent configurations reveals important dehydrogenation and re-hydrogenation steps of the -NH$_2$ group bound to the Cu-site that are essential to catalyst recovery. This work illustrates the importance of ensemble solvent configurational sampling to reveal the breadth of processes that underpin the full catalytic cycle.<br>

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