Surface Structure Sensitivity of Hydrodeoxygenation of Biomass-derived Organic Acids over Palladium Catalysts: A Microkinetic Modeling Approach

2021 ◽  
Author(s):  
Subrata K. Kundu ◽  
Vijay Solomon Rajadurai ◽  
Wenqiang Yang ◽  
Eric Walker ◽  
Osman Mamun ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Organic Acids ◽  
Organic Acid ◽  
Palladium Catalysts ◽  
Density Functional ◽  
Transition State Theory ◽  
State Theory ◽  
Propanoic Acid ◽  
Functional Theory

Microkinetic models based on parameters obtained from density functional theory and transition state theory have been developed for the hydrodeoxygenation (HDO) of propanoic acid, a model lignocellulosic biomass-derived organic acid,...

Theoretical calculations of rate of NDMA formation from gramine

2013 ◽  
Vol 91 (4) ◽  
pp. 275-282
Author(s):  
F. Shojaie ◽  
M. Dehestani
Keyword(s):  
Reaction Mechanism ◽  
Transition State ◽  
Density Functional ◽  
Transition State Theory ◽  
Theoretical Calculations ◽  
State Theory ◽  
Stationary Points ◽  
Functional Theory ◽  
Molecule Reaction ◽  
Good Agreement

The first ab initio theoretical study is performed on the ion–molecule reaction of gramine (C11H14N2) with NO+ for the formation of N-nitrosodimethylamine (NDMA). The reaction mechanism is investigated using the B3LYP density functional theory level. The stationary points along the reaction energy profile have been calculated at the B3LYP/6-311+G(d,p) level of the theory in the gas phase and solution phase. In this work, an attempt is made to elucidate the mechanism and so is proposed the efficient reactive pathway for the reaction of gramine with NO+ step by step. A complete reaction mechanism has been established, and the temperature dependence of all rate constants between 23 and 65 °C are reported and analyzed in terms of transition state theory. The percentages of NDMA formation in the 23–65 °C temperature range have been calculated in aqueous solution by transition state theory. The results are in good agreement with experimental results.

A novel mechanism of spin-orientation dependence of O2 reactivity from first principles methods

2017 ◽  
Vol 7 (5) ◽  
pp. 1040-1044 ◽  
Author(s):  
M. C. S. Escaño ◽  
H. Kasai
Keyword(s):  
Density Functional Theory ◽  
Charge Transfer ◽  
Transition State ◽  
First Principles ◽  
Density Functional ◽  
Orientation Dependence ◽  
Coupling Mechanism ◽  
Spin Moment ◽  
Spin Orientation ◽  
Functional Theory

A novel mechanism of oxygen reaction on a metal surface beyond the present charge transfer or hybridization mechanism, spin-orientation dependence via a coupling mechanism due to the finite spin moment of O2 at the transition state, is obtained using a combination of spin density functional theory (SDFT) and constrained DFT.

A time-dependent density functional theory (TDDFT) interpretation of the optical spectra of zinc phthalocyanine π-cation and π-anion radicals

2009 ◽  
Vol 87 (7) ◽  
pp. 994-1005 ◽  
Author(s):  
Angela Rosa ◽  
Giampaolo Ricciardi
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Cation Radical ◽  
State Theory ◽  
Time Dependent ◽  
Zinc Phthalocyanine ◽  
Functional Theory ◽  
Satisfactory Description ◽  
Dependent Density ◽  
Anion Radicals

The UV–visible and near-IR spectra of the zinc phthalocyanine π-cation and π-anion radicals, [ZnPc(–1)]•+ and [ZnPc(–3)]•–, are investigated by time-dependent density functional theory (TDDFT) calculations using the pure, asymptotically correct, statistical average of (model) orbital potentials (SAOP) functional. The nature and intensity of the main spectral features are highlighted and interpreted on the basis of the ground-state electronic structure of the complexes. Similarities and differences with previous TDDFT/B3LYP results are discussed. TDDFT/SAOP results for the π-anion radical prove to be in excellent agreement with the solution spectra and generally in line with deconvolution analyses of solution absorption and magnetic circular dichroism (MCD) spectra. On the basis of these results a novel interpretation of the Q-band system is proposed. For the π-cation radical TDDFT/SAOP calculations provide a satisfactory description of the UV region of the spectrum. However, they do not reproduce accurately the energy and intensity of the Q band observed at 825 nm. The description of the Q-band region appears to be complicated by the presence of spurious non-Gouterman transitions. Furthermore, the calculations, either in the gas phase or in solution, do not account for the broad absorption near 500 nm that has been suggested to arise from a nondegenerate, z-polarized 2A2g excited state. Theory and experiment can be reconciled if the presence of an axial ligand such as CN– is explicitly considered in the calculations. TDDFT/SAOP results for the axially ligated [ZnPc(–1)(CN)]• species indicate that the 500 nm feature is related to the axial ligation induced symmetry lowering of the π-cation radical and this band is assigned to a z-polarized transition associated with the hole in the 2a1u.

scholarly journals Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

2017 ◽  
Vol 13 ◽  
pp. 1969-1976 ◽  
Author(s):  
José Enrique Barquera-Lozada ◽  
Gabriel Cuevas
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Density Functional ◽  
Chair Conformation ◽  
High Energy ◽  
Functional Theory ◽  
Sigmatropic Rearrangements ◽  
The Density Functional Theory ◽  
Reaction Proceeds ◽  
Cope Rearrangements

It has been proposed that elemanes are biogenetically formed from germacranes by Cope sigmatropic rearrangements. Normally, this reaction proceeds through a transition state with a chair conformation. However, the transformation of schkuhriolide (germacrane) into elemanschkuhriolide (elemane) may occur through a boat transition state due to the final configuration of the elemanschkuhriolide, but this transition state is questionable due to its high energy. The possible mechanisms of this transformation were studied in the density functional theory frame. The mechanistic differences between the transformation of (Z,E)-germacranes and (E,E)-germacranes were also studied. We found that (Z,E)-germacranolides are significantly more stable than (E,E)-germacranolides and elemanolides. In the specific case of schkuhriolide, even when the boat transition state is not energetically favored, a previous hemiacetalization lowers enough the energetic barrier to allow the formation of a very stable elemanolide that is even more stable than its (Z,E)-germacrane.

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