Application of Ab Initio Quantum Mechanical Calculations to Investigate Oxidation of C-7 and C-14 Methyl Esters: An Alternative Fuel

2009 ◽  
Author(s):  
I. Shafagh ◽  
K. J. Hughes ◽  
M. Pourkashanian ◽  
A. Williams
Keyword(s):  
Density Functional ◽  
Methyl Esters ◽  
Carbon Number ◽  
State Theory ◽  
Basis Set ◽  
Functional Theory ◽  
Bimolecular Reactions ◽  
The Density Functional Theory ◽  
Complete Basis Set ◽  
The One

Using Gaussian 03 [1] program the electronic structure of the C-14 methyl ester, C14H28O2 (methyl tridecanoate), one of the components of biodiesel and the species involved in the unimolecular and bimolecular decompositions of it were estimated. For the electronic calculations the density functional theory (DFT) at B3LYP/6-311G(d, p) level and complete basis set (CBS-QB3) were applied. Using the KHIMERA program [2], contributions from energies, harmonic vibrational frequencies and moments of inertia were utilized to construct modified Arrhenius rate expressions for bimolecular reactions. C7H14O2 was selected as a surrogate for the C14H28O2 fuel in order to study the bimolecular reactions with flame radicals. In the present work reactions of carbons number 5 and 6 of C7H14O2, where carbon number 1 is the one single bonded to oxygen atom, with flame reactive radicals such as CH3, HO2 and H were studied. The rate expressions for the cited reactions were estimated using transition state theory as implemented in KHIMERA, over the temperature 500–2000 K. Heat of reactions for unimolecular decompositions were also calculated and compared to those from Methyl Butanoate (MB).

Application of Ab Initio Quantum Mechanical Calculations to Investigate Oxidation of C-7 and C-14 Methyl Esters: An Alternative Fuel

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
I. Shafagh ◽  
K. J. Hughes ◽  
M. Pourkashanian
Keyword(s):  
Density Functional ◽  
Methyl Esters ◽  
Carbon Number ◽  
Software Tool ◽  
State Theory ◽  
Basis Set ◽  
Bimolecular Reactions ◽  
Dissociation Energies ◽  
Complete Basis Set ◽  
The One

Using the GAUSSIAN 03 (Frisch et al., 2004, GAUSSIAN 03, Revision C.02, Gaussian, Inc., Wallingford, CT) program, the electronic structure of the C-14 and C-7 methyl esters, C14H28O2 (methyl tridecanoate) and C7H14O2 (methyl hexanoate), was estimated. For the electronic calculations, the density functional theory at the B3LYP/6-311G(d,p) level and the complete basis set (CBS-QB3) were applied. Bond dissociation energies for C-14 and C-7 esters were evaluated and compared with those of methyl butanoate, C5H10O2. Using the KHIMERA program (2007, KHIMERA04, Version 1.1, Motorola Inc; Novoselov et al., 2002, “CHIMERA: A Software Tool for Reaction Rate Calculations and Kinetics and Thermodynamics Analysis,” J. Comput. Chem., 23, pp. 1375–1389), contributions from energies, harmonic vibrational frequencies, and moments of inertia were utilized to construct modified Arrhenius rate expressions for bimolecular reactions. C7H14O2 was selected as a surrogate for the C14 fuel in order to study the bimolecular reactions with flame radicals. In the present work, reactions of carbon numbers 4 and 5 of C7H14O2, where carbon number 1 is the one single bonded to oxygen atom, with flame reactive radicals such as CH3, HO2, and H were studied where the rates for the reactions of other carbon sites can be obtained from studying methyl butanoate’s reactions. The rate expressions were estimated using transition state theory as implemented in KHIMERA over the temperature of 500–2000 K.

Evaluating Transition Metal Barrier Heights with the Latest DFT Exchange–Correlation Functionals – the MOBH35 Benchmark Dataset

2019 ◽  
Author(s):  
Mark Iron ◽  
Trevor Janes
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Set ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Barrier Heights ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
Hybrid Functionals

A new database of transition metal reaction barrier heights – MOBH35 – is presented. Benchmark energies (forward and reverse barriers and reaction energy) are calculated using DLPNO-CCSD(T) extrapolated to the complete basis set limit using a Weizmann1-like scheme. Using these benchmark energies, the performance of a wide selection of density functional theory (DFT) exchange–correlation functionals, including the latest from the Truhlar and Head-Gordon groups, is evaluated. It was found, using the def2-TZVPP basis set, that the ωB97M-V (MAD 1.8 kcal/mol), ωB97X-V (MAD 2.1 kcal/mol) and SCAN0 (MAD 2.1 kcal/mol) hybrid functionals are recommended. The double-hybrid functionals PWPB95 (MAD 1.6 kcal/mol) and B2K-PLYP (MAD 1.8 kcal/mol) did perform slightly better but this has to be balanced by their increased computational cost.

scholarly journals Density Functional Theory and Complete Basis Set Ab Initio Computational Study of Five-, Six-, Seven- and Eight-hydrogen Coordinated Carbon Cations

1999 ◽  
Vol 23 (8) ◽  
pp. 502-503
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
Complete Basis ◽  
Complete Basis Set ◽  
High Level

High level ab initio and density functional theory studies are performed on highly protonated methane species.

scholarly journals Computational Evidence Suggests That 1-chloroethanol May Be an Intermediate in the Thermal Decomposition of 2-chloroethanol into Acetaldehyde and HCl

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Oscar Ventura ◽  
Vincenzo Barone
Keyword(s):  
Aqueous Solution ◽  
Water Molecule ◽  
Gas Phase ◽  
Density Functional ◽  
Water Molecules ◽  
Functional Theory ◽  
Direct Transformation ◽  
The Density Functional Theory ◽  
Successive Step ◽  
The One

<p>The dehalogenation of 2-chloroethanol (2ClEtOH) in gas phase with and without participation of catalytic water molecules has been investigated using methods rooted into the density functional theory. The well-known HCl elimination leading to vinyl alcohol (VA) was compared to the alternative elimination route towards oxirane and shown to be kinetically and thermodynamically more favorable. However, the isomerization of VA to acetaldehyde in the gas phase, in the absence of water, was shown to be kinetically and thermodynamically less favorable than the recombination of VA and HCl to form the isomeric 1-chloroethanol (1ClEtOH) species. This species is more stable than 2ClEtOH by about 6 kcal mol<sup>-1</sup>, and the reaction barrier is 22 kcal mol<sup>-1</sup> vs 55 kcal mol<sup>-1</sup> for the direct transformation of VA to acetaldehyde. In a successive step, 1ClEtOH can decompose directly to acetaldehyde and HCl with a lower barrier (29 kcal mol<sup>-1</sup>) than that of VA to the same products (55 kcal mol<sup>-1</sup>). The calculations were repeated using a single ancillary water molecule (W) in the complexes 2ClEtOH_W and 1ClEtOH_W. The latter adduct is now more stable than 2ClEtOH_W by about 8 kcal mol<sup>-1</sup>, implying that the water molecule increased the already higher stability of 1ClEtOH in the gas phase. However, this catalytic water molecule lowers dramatically the barrier for the interconversion of VA to acetaldehyde (from 55 to 6 kcal mol<sup>-1</sup>). This barrier is now smaller than the one for the conversion to 1ClEtOH (which also decreases, but not so much, from 22 to 12 kcal mol<sup>-1</sup>). Thus, it is concluded that while 1ClEtOH may be a plausible intermediate in the gas phase dehalogenation of 2ClEtOH, it is unlikely that it plays a major role in water complexes (or, by inference, aqueous solution). It is also shown that neither in the gas phase nor in the cluster with one water molecule, the oxirane path is competitive with the VA alcohol path.</p>

A Density Functional Theory Study of the Isomerization of Substituted 2and#39;-hydroxychalcones to the Corresponding Flavanones

2021 ◽  
Vol 43 (1) ◽  
pp. 25-25
Author(s):  
Said Abdelqadar Said Said Abdelqadar Said ◽  
Omar A Shareef and Abdulkhalik S Alkazzaz Omar A Shareef and Abdulkhalik S Alkazzaz
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Ring Closure ◽  
Basis Set ◽  
Functional Theory ◽  
Rate Determining Step ◽  
The Density Functional Theory ◽  
Electronic And Structural Properties ◽  
Maximum Hardness Principle

The transformation of 2and#39;-hydroxychalcones to their corresponding flavanones was studied theoretically by the use of the density functional theory (DFT) with B3-LYP/ 6-311G basis set to get important information about the role of both of electronic and structural properties in this process. The obtained energies were found to be in agreement with our previous results that obtained from HPLC studies. The estimated hardness, polarizability, and electrophilicity profiles were found to obey the maximum hardness principle (MHP), minimum polarizability principle (MPP), and the minimum electrophilicity principle (MEP) respectively. Flavanone ring closure was found to be the rate-determining step.

Electronic and structural study of hexagonal TiC nanowires: ab initio study

BIBECHANA ◽  
2018 ◽  
Vol 16 ◽  
pp. 7-14 ◽  
Author(s):  
Puspa Raj Adhikari ◽  
Om Prakash Upadhyay ◽  
Gopi Chandra Kaphle ◽  
Anurag Srivastava
Keyword(s):  
Density Functional ◽  
Small Diameter ◽  
Hexagonal Structure ◽  
Density Of State ◽  
Electronic Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The One ◽  
The Impact ◽  
Bulk Structures

Nanowire are the one-dimensional nanostructure with the diameter order of one to few hundred nanometre. These structure shows unique properties other than their bulk structures. In this article, a qualitative first principle discussion of TiC nanowire is reported, indicating the impact of DFT based GGA relativistic corrections on its electronic properties. Here, we analyse   the Titanium Carbide (TiC) nanowire of hexagonal structure periodic in Z-direction with the density functional theory (DFT). The GGA with RBBE Correlation analysis of this material shows the metallic characteristics in its bulk but the electronic density of  state shows that the hybridization state are different from their bulk when the material is analysed in nanostructure form. Three structures of hexagonal TiC nanowire directed in (1,1,1) plane were analysed to explore diameter (4-18) Å dependent comparative study of electronic, stabilizing and optical property which shows unique different result counterparts to its bulk. Hexagonal TiC nanowire were found to be semiconducting with narrow band gap (0.21-0.34) eV in small diameter while metallic in higher diameter. They are comparable stables as their bulk for higher structure. Similarly, for the same investigation, the structures are cross checked by surface atom passivation to verify the reliability of the result that we found.BIBECHANA 16 (2019) 7-14

Complete basis set, hybrid-density functional theory study, and natural bond orbital interpretations of the conformational behavior of halocarbonyl, thiocarbonyl, and selenocarbonyl isocyanates

2012 ◽  
Vol 90 (4) ◽  
pp. 333-343 ◽  
Author(s):  
Seiedeh Negar Mousavi ◽  
Davood Nori-Shargh ◽  
Hooriye Yahyaei ◽  
Kobra Mazrae Frahani
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Difference ◽  
Basis Set ◽  
Hybrid Density Functional Theory ◽  
Total Dipole Moment ◽  
Functional Theory ◽  
Complete Basis Set ◽  
Conformation Stability ◽  
Hybrid Density Functional

Complete basis set CBS-QB3, hybrid-density functional theory (B3LYP/Def2-TZVPP) based methods and NBO interpretation were used to investigate the impacts of the stereoelectronic effects and electrostatic and steric interactions on the conformational properties of halocarbonyl isocyanates (halo = F (1), Cl (2), and Br (3)), halothiocarbonyl isocyanates (halo = F (4), Cl (5), and Br (6)), and haloselenocarbonyl isocyanates(halo = F (7), Cl (8), and Br (9)). Both methods showed that the Z-conformations of compounds 1, 4, and 7 are more stable than their corresponding E conformations, but the stability of the E conformations, when compared with the corresponding Z conformations, increases from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. The NBO analysis showed that the generalized anomeric effect (GAE) is in favor of the Z conformations of compounds 1, 4, and 7. The GAE values calculated (i.e., GAEE–GAEZ) increase from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. On the other hand, there are none of the same trends between the calculated total dipole moment and the Gibbs free energy difference values between the E and Z conformations (i.e., ΔμE–Z and ΔGE–Z) of compounds 1–3, 4–6, and 7–9. Accordingly, the GAE succeeds in accounting for the increase of the E conformation stability from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. Therefore, the GAE associated with the electron delocalization, not the total dipole moment changes (i.e., ΔμE–Z), is a reasonable indicator of the total energy difference in compounds 1–3, 4–6, and 7–9. There is a direct correlation between the calculated GAE and Δ[r2–6(E) – r2–6(Z)] parameters. Importantly, there are interesting through-space electron delocalizations (LP2X6→π*C4–O5) that justify the increase of the E conformation stability from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9, when compared with their corresponding Z conformations. The correlations between the GAE, bond orders, total steric exchange energies (TSEE), ΔGZ–E, ΔμE–Z, structural parameters, and conformational behaviors of compounds 1–9 were investigated.

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