scholarly journals Hydrodeoxygenation of Guaiacol Over Orthorhombic Molybdenum Carbide: A DFT and Microkinetic Study

2021 ◽  
Author(s):  
Kushagra Agrawal ◽  
Alberto Roldan ◽  
Nanda Kishore ◽  
Andrew J Logsdail
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Molybdenum Carbide ◽  
Activation Barrier ◽  
Reaction Energy ◽  
Functional Theory

The hydrodeoxygenation of guaiacol is modelled over a (100) β-Mo2C surface using density functional theory and microkinetic simulations. The thermochemistry of the process shows that the demethoxylation of the guaiacol, to form phenol, will be the initial steps, with a reaction energy of 29 kJ/mol (i.e. endothermic) and a highest activation barrier of 112 kJ/mol. Subsequently, the dehydroxylation of the phenol, which has a rate-determining activation barrier of 145 kJ/mol, will lead to the formation of benzene, with an overall reaction energy for conversion from guaiacol of -91 kJ/mol (i.e. exothermic).

scholarly journals Surprisingly facile CO2 insertion into cobalt alkoxide bonds: A theoretical investigation

2015 ◽  
Vol 11 ◽  
pp. 1340-1351 ◽  
Author(s):  
Willem K Offermans ◽  
Claudia Bizzarri ◽  
Walter Leitner ◽  
Thomas E Müller
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Density Functional Theory ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Activation Barrier ◽  
Density Functional Theory Calculations ◽  
Reaction Energy ◽  
Reaction Step ◽  
Functional Theory

Exploiting carbon dioxide as co-monomer with epoxides in the production of polycarbonates is economically highly attractive. More effective catalysts for this reaction are intensively being sought. To promote better understanding of the catalytic pathways, this study uses density functional theory calculations to elucidate the reaction step of CO2 insertion into cobalt(III)–alkoxide bonds, which is also the central step of metal catalysed carboxylation reactions. It was found that CO2 insertion into the cobalt(III)–alkoxide bond of [(2-hydroxyethoxy)CoIII(salen)(L)] complexes (salen = N,N”-bis(salicyliden-1,6-diaminophenyl)) is exothermic, whereby the exothermicity depends on the trans-ligand L. The more electron-donating this ligand is, the more exothermic the insertion step is. Interestingly, we found that the activation barrier decreases with increasing exothermicity of the CO2 insertion. Hereby, a linear Brønsted–Evans–Polanyi relationship was found between the activation energy and the reaction energy.

A density functional theory study on the performance of graphene and N-doped graphene supported Au3 cluster catalyst for acetylene hydrochlorination

2016 ◽  
Vol 94 (10) ◽  
pp. 842-847 ◽  
Author(s):  
Fei Zhao ◽  
Yang Wang ◽  
Lihua Kang
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Gap ◽  
Activation Barrier ◽  
Similar Reaction ◽  
Functional Theory ◽  
Acetylene Hydrochlorination ◽  
Doped Graphene ◽  
Calculated Activation ◽  
Calculated Activation Barrier

Density functional theory (DFT) calculation was used to investigate the mechanism of Au3 clusters, separately supported on pure graphene (Au3/graphene) and one graphitic N-doped graphene (Au3/N-graphene). These supported Au3 clusters were used to catalyze acetylene hydrochlorination. Results show that the graphene supporter could obviously enhance the adsorption of reactants. Also, N-atom doping could broaden the energy gap between the HOMO of graphene and the LUMO of Au3, leading to the significantly attenuated interaction between the Au3 cluster and graphene by more than 19 kcal/mol (1 cal = 4.184 J). The two catalysts possessed extremely similar reaction mechanisms with activation energy values of 23.26 and 23.89 kcal/mol, respectively. The calculated activation barrier declined in the order of Au3 < Au3/N-graphene < Au3/graphene, suggesting that Au3/N-graphene could be a potential catalyst for acetylene hydrochlorination.

scholarly journals Adsorption of iron tetraphenylporphyrin on (111) surfaces of coinage metals: a density functional theory study

2017 ◽  
Vol 8 ◽  
pp. 2484-2491 ◽  
Author(s):  
Hao Tang ◽  
Nathalie Tarrat ◽  
Véronique Langlais ◽  
Yongfeng Wang
Keyword(s):  
Density Functional Theory ◽  
High Spin ◽  
Density Functional ◽  
Activation Barrier ◽  
High Spin State ◽  
Coulomb Repulsion ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Intermediate Spin ◽  
Magnetic States

The adsorption of the iron tetraphenylporphyrin (FeTPP) molecule in its deckchair conformation was investigated on Au(111), Ag(111) and Cu(111) surfaces by performing spin-polarized density functional theory (DFT) calculations taking into account both van der Waals (vdW) interaction and on-site Coulomb repulsion. The deckchair conformation of the molecule favours intermolecular π–π-type interactions in a less densely packed monolayer than the saddle conformation. The activation barrier between the two stable magnetic states (high spin, S = 2 and intermediate spin, S = 1) of the molecule in vacuum disappears upon adsorption on the metal surfaces. The high-spin state of physisorbed FeTPP is stable on all adsorption sites. This result reveals that an external permanent element such as a STM tip or an additional molecule is needed to use FeTPP or similar molecules as model system for molecular spin switches.

scholarly journals Density functional theory (DFT) calculations of conformational energies and interconversion pathways in 1,2,7-thiadiazepane

2011 ◽  
Vol 76 (3) ◽  
pp. 395-406 ◽  
Author(s):  
Mina Haghdadi ◽  
Nahid Farokhi
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Activation Barrier ◽  
Stable Conformer ◽  
Functional Theory ◽  
Conformational Interconversion ◽  
Interconversion Barrier ◽  
The One ◽  
Twist Boat

The molecular structure and conformational analysis of 1,2,7-thiadiazapane conformers were investigated by density functional theory (DFT) calculations at the B3LYP/cc-pVDZ level of theory. Four twist-chair (TC), six twist-boat (TB), two boat (B), two chair (C) and four twist (T) conformers were identified as minima and transition states for 1,2,7-thiadiazepane. The TC1 conformer is the most stable conformer and the twist-chair conformers are predicted to be lower in energy than their corresponding boat and chair conformations. DFT predicts a small barrier to pseudo-rotation and a remarkable activation barrier for the conformational interconversion of the twist-chair conformers to their corresponding boat conformers. The simplest conformational process and the one with the lowest barrier is the degenerate interconversion of the twist-chair 3 (TC3) conformation with itself via the CS symmetric chair (C2) transition state. The calculated strain energy barrier for this process is 2.41 kJ mol-1. The highest conformational interconversion barrier is between TC2 and twistboat 3 (TB3) forms, which was found to be 75.62 kJ mol-1.

Facile formation of azines from reactions of singlet methylene and dimethylcarbene with precursor diazirines: theoretical explorations

1999 ◽  
Vol 77 (5-6) ◽  
pp. 540-549 ◽  
Author(s):  
Gennady V Shustov ◽  
Michael TH Liu ◽  
K N Houk
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Ring Opening ◽  
Density Functional ◽  
Activation Barrier ◽  
Thermal Reaction ◽  
Orbital Theory ◽  
Functional Theory ◽  
Activation Barriers ◽  
Singlet Methylene

The reactions of the singlet methylene (1a) and dimethylcarbene (1b), with their diazirine precursors, diazirine (2a), and dimethyldiazirine (2b), have been studied theoretically using ab initio and density functional theory. The reaction has no activation barriers for the parent system (1a + 2a) and proceeds via a reactive complex and a transition state with a small negative enthalpy of activation Δ Hnot =298 = -1.1 kcal mol-1, ΔSnot =298 = -34.4 cal mol-1 K-1, ΔG°298 = 9.2 kcal mol-1) for the dimethyl derivatives (1b + 2b). The formation of N-methylene diazirinium ylides (3a,b) is exothermic by 64-80 kcal mol-1. The isomer, 1,3-diazabicyclo[1.1.0]butane (4a), is more stable (5-12 kcal mol-1) than isomer 3a, but can neither be formed by direct thermal reaction of 1a with 2a nor undergo the direct rearrangement into formaldazine (5a). The rearrangement of ylides 3a,b into azines 5a,b proceeds by conrotatory C3-N1 ring opening. The predicted activation barrier of ca. 15 kcal mol-1 for the ring opening in ylide 3b is in excellent agreement with experimental data. The formation of pyridinium ylides from carbenes and pyridine is also studied.Key words: diazirinium ylide, ab initio MO (molecular orbital) theory, density functional theory, pyridinium ylide, CIS (singles configuration interaction) transition energies.

Carbon–hydrogen vs. carbon–halogen oxidative addition of chlorobenzene to a cationic iridium(I) system — A density functional theory study

2009 ◽  
Vol 87 (10) ◽  
pp. 1460-1469 ◽  
Author(s):  
Hong Wu ◽  
Michael B. Hall
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Activation Barrier ◽  
Experimental Results ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
System A ◽  
Oxidative Additions ◽  
Calculated Activation ◽  
Calculated Activation Barrier

Density functional theory (DFT) is used to explore the competitive C−H and C−Cl oxidative additions (OA) of chlorobenzene to the cationic Ir(I) complex: [(PNP*)IrI]+ [PNP* = 2,6-bis((dimethylphosphino)methyl)pyridine]. Consistent with experimental results, the calculated activation barrier for C−H OA (ΔG‡ = 10.7 kcal mol–1) is lower than that for C−Cl OA (ΔG‡ = 19.7 kcal mol–1). However, the C−Cl OA product is calculated to be thermodynamically preferred as its ΔGo is 14.3 kcal mol–1 below that for the most stable C−H OA product.

Does OF2 Form Stable Transition Metal Complexes?. A Density Functional Investigation of the System (OC)5Cr/OF2

1993 ◽  
Vol 48 (10) ◽  
pp. 1348-1354 ◽  
Author(s):  
Heiko Jacobsen ◽  
Heinz-Bernhard Kraatz ◽  
Tom Ziegler ◽  
Philip Michael Boorman
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Activation Barrier ◽  
Local Density ◽  
Density Approximation ◽  
Functional Theory ◽  
Functional Investigation ◽  
Metal Fragment

Density Functional Theory (DFT) within the Local Density Approximation (LDA) was employed to calculate the reaction of OF2 with the metal fragment Cr(CO)5. It is demonstrated that OF2 does not show simple ligand behavior but reacts with the transition metal fragment under oxidative addition, leading to a chromium oxo-complex and transforming two cis CO into fluoroformyl ligands. We calculated this reaction to proceed without any major activation barrier and to be exothermic by about 100 kcal/mol. A possible mechanism for this reaction is discussed

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