scholarly journals Theoretical Study of the Interconversions of Selected Isomers from C8H13+ System : A DFT level of Study

2019 ◽  
Vol 35 (2) ◽  
pp. 792-797
Author(s):  
Joseph Lianbuanga ◽  
Zodinpuia Pachuau
Keyword(s):  
Activation Energy ◽  
Density Functional ◽  
Theoretical Study ◽  
Basis Set ◽  
Energy Profile ◽  
Stable Isomer ◽  
Geometrical Analysis ◽  
Functional Theory ◽  
System A ◽  
Eigen Value

The selected isomers of C8H13+ are calculated to predict its relative energies and their stability for each species at the levels of density functional theory (DFT) using 6-311G+dp basis set. We also attempted to predict the isomerisation or mechanistic pathways by locating the transition States through the interruption of diagonal matrix as confirmed by the imaginary Eigen value one. The isomers of the known and new isomers are revealed and analysed after optimisation. The geometrical analysis proposed that Iso- VII might be the most stable isomer which is also proved by heat of reactions analysis and the activation energy of all the inter conversions are compared in the energy profile diagram.

Theoretical Study of Ethylene Addition to O=W(=CH2)(CH3)2

2007 ◽  
Vol 62 (3) ◽  
pp. 367-372 ◽  
Author(s):  
Robin Haunschild ◽  
Gernot Frenking
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Reaction Pathways ◽  
Theoretical Studies ◽  
Stable Isomer ◽  
Functional Theory ◽  
B3lyp Level ◽  
Rhenium Compound ◽  
Favorable Reaction

Quantum chemical calculations using density functional theory at the B3LYP level of theory were carried out to investigate the reaction pathways for the addition of ethylene to WO(CH3)2(CH2) (W1). The results are compared to those of previous theoretical studies of the ethylene addition to OsO3(CH2) (Os1) and ReO2(CH3)(CH2) (Re1). The theoretically predicted reactions pathways exhibit significant differences. The energetically most favourable reaction of the tungsten system W1 is the [2+2]W,C addition across theW=C double bond yielding the metallacyclobutane W3a which then rearranges to the slightly more stable isomer W3b. The [2+2]Re,C addition of the rhenium compound yielding the metallacyclobutane Re3a has the lowest activation barrier for the ethylene addition to the rhenium system, but the reaction is endothermic while the exothermic formation of the more stable isomer Re3b has a much higher activation barrier. The [3+2]C,O addition Os1+C2H4→Os2 is the thermodynamically most favorable reaction of the osmium compound.

Theoretical investigation of some N-nitrosodiphenylamine biological molecules — A natural bond orbital (NBO) study

2011 ◽  
Vol 89 (10) ◽  
pp. 1230-1235
Author(s):  
Xiao-Hong Li ◽  
Rui-Zhou Zhang ◽  
Xian-Zhou Zhang
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Biological Molecules ◽  
Basis Set ◽  
Natural Hybrid ◽  
Functional Theory ◽  
Molecular Stability ◽  
Hybrid Orbitals

Theoretical study of several N-nitrosodiphenylamine biological molecules has been performed using quantum computational ab initio RHF and density functional B3LYP and B3PW91 methods with 6–311G++(d,p) basis set. Geometries obtained from density functional theory (DFT) calculations were used to perform Natural bond orbital (NBO) analysis. The p characters of two nitrogen natural hybrid orbitals (NHOs) σN3−N2 increase with increasing σp values of the substituents on the benzene, which results in a lengthening of the N3–N2 bond. The p characters of oxygen NHO σO1−N2 and nitrogen NHO σO1−N2 bond orbitals decrease with increasing σp values of the substituents on the benzene, which results in a shortening of the N2=O1 bond. It is also noted that decreased occupancy of the localized σN3−N2 orbital in the idealized Lewis structure, or increased occupancy of [Formula: see text]of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are also related to the resulting p character of the corresponding nitrogen NHO of σN3−N2 bond orbital.

scholarly journals Theoretical study on the mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile catalyzed by lithium ethoxide

2008 ◽  
Vol 6 (2) ◽  
pp. 304-309 ◽  
Author(s):  
Qi-Shan Hu ◽  
Lai-Cai Li ◽  
Xin Wang
Keyword(s):  
Activation Energy ◽  
Vibration Analysis ◽  
Density Functional ◽  
Theoretical Study ◽  
Transition States ◽  
Functional Theory ◽  
Bond Forming ◽  
Uncatalyzed Reaction ◽  
Mechanism Of Reaction ◽  
Reaction Processes

AbstractThe The mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile for the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2,5-dihydrofuran-3-carbonitrile catalyzed by lithium ethoxide was investigated by density functional theory (DFT). The geometries and the frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-31G(d) level. The vibration analysis and the IRC analysis verified the authenticity of transition states. The reaction processes were confirmed by the changes of charge density at the bond-forming critical point. The results indicated that lithium ethoxide is an effective catalyst in the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2, 5-dihydrofuran-3-carbonitrile from malononi-trile and 3-hydroxy-3-methyl-2-butanone. The activation energy of the reaction with lithium ethoxide was 115.86 kJ·mol−1 less than the uncatalyzed reaction. The mechanism of the lithium ethoxide catalyzed reaction differed from the mechanism of the uncatalyzed reaction.

Theoretical Study of 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane (TEX)

2012 ◽  
Vol 554-556 ◽  
pp. 1618-1623 ◽  
Author(s):  
Xiu Lin Zeng ◽  
Xue Hai Ju ◽  
Hong Xu Gao
Keyword(s):  
Strain Energy ◽  
Density Functional ◽  
Theoretical Study ◽  
Large Strain ◽  
Heat Of Formation ◽  
Basis Set ◽  
Isodesmic Reaction ◽  
Detonation Pressure ◽  
Functional Theory ◽  
B3lyp Method

The heat of formation (HOF) for a caged owurtzitane analogue compound of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diaza-tetracyclododecane (TEX) was obtained by density functional theory B3LYP method with 6-31+G** basis set. The isodesmic reaction, instead of atomization reaction, makes good use of the available experimental data of HOFs and thus ensures the credibility of the result. The value of HOF of TEX is –448.37 kJ/mol. The predicted detonation velocity is about 8.2 km/s and detonation pressure is 31.44 GPa. The dissociation energy for the N-NO2 bond of TEX is 165.43 kJ/mol. There is large strain in TEX with strain energy of 62.47 kJ/mol. The nitro group interaction in TEX is small.

Theoretical Study on the Isomerization Reaction Mechanism of the Chain-Isomers of N9H9

2014 ◽  
Vol 887-888 ◽  
pp. 677-683
Author(s):  
Shu Zhang ◽  
Xiao Lan Wang ◽  
Wan Fei Cai ◽  
Lai Cai Li ◽  
An Min Tian
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Basis Set ◽  
Isomerization Reaction ◽  
Thermochemical Properties ◽  
Reaction Energy ◽  
Functional Theory ◽  
B3lyp Method ◽  
Isomerization Processes

Density functional theory B3LYP method with 6-311++G** basis set has been used to optimize Chain-isomers of N9H9. Sixteen species are found, the structures, stabilities, thermochemical properties, and their tautomerism are studied and discussed. The ten corresponding transition states have been found. The experimental results indicated that the reaction energy barriers of isomerization of these isomers were between 139.56 kJ/mol and 236.67kJ/mol. The activation energies is higher, the isomerization of these isomers is relatively difficult. The isomerization processes of these chain-isomers of N9H9 are all completed by the H transfer.

Theoretical Study on Au-Doped Ge Semiconductor Clusters

2013 ◽  
Vol 634-638 ◽  
pp. 2537-2540
Author(s):  
Xiao Jun Li
Keyword(s):  
Vibrational Frequency ◽  
Density Functional ◽  
Theoretical Study ◽  
Chemical Shifts ◽  
Theoretical Work ◽  
Basis Set ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Germanium Clusters

Structure, electronic property, aromaticity and vibrational frequency of medium-sized Au-doped germanium clusters were systematically explored using the density-functional theory (DFT) in conjunction with the LanL2DZ basis set. Our results show that the endohedrally Au-doped cagelike structures are energetically preferred. The p- and d-states in endohedral Au atom mainly contribute to the chemical bonding at around −6.5 and −10.6 eV for the AuGe10 and AuGe12 clusters. Moreover, the cage aromaticity appears to be an important determination of the electronic stability of the two clusters, reflected by negative nucleus-independent chemical shifts (NICS) values. The theoretical work will be useful and helpful for the understanding in the further application, i.e., cluster-assembled optoelectronic nanomaterials.

scholarly journals Theoretical Study of the [4+2] Cycloaddition Reaction of Trifluoroethylene with Five-membered Chalcogens Heterocyclic Compounds

2019 ◽  
Vol 7 (2) ◽  
pp. 69-77
Author(s):  
Haydar A. Mohammad-Salim ◽  
Hassan H. Abdallah
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Theoretical Study ◽  
Cycloaddition Reaction ◽  
Branching Ratio ◽  
Basis Set ◽  
Stationary Points ◽  
Functional Theory ◽  
Highest Occupied Molecular Orbital ◽  
Synthesis Reactions

[4+2] cycloaddition reaction has enormous significant in organic chemistry synthesis reactions and yet remains unexplored for the synthesis of fluorine-containing compounds. A density functional theory study of the stereo- and regioselectivity of the [4+2] cycloaddition reaction of trifluoroethylene with furan, thiophene, and selenophene was carried out in the gas phase. The B3LYP functional is used throughout in combination with 6-31G(d) basis set. The analysis of stationary points and the energetic parameters indicates that the reaction mechanism is concerted and confirms that the exo-adducts are thermodynamically and kinetically more favored than endo-adducts. The calculated branching ratio indicates that the exo-adducts have the higher percent yield than endoadducts and the yield of endo-adducts is increased only slightly on proceeding from furan, through thiophene, and onto selenophene. The analysis of the frontier molecular highest occupied molecular orbital (MO) and lowest unoccupied MO orbitals indicates that the exo-adducts are more stable due to their higher energy gab. The reaction energies were compared to the MP2/6-31G(d) and CCSD(T)/6-31G(d) calculations.

scholarly journals Estimation of the Efficiency of Corrosion Inhibition by Zn-Dithiocarbamate Complexes: a Theoretical Study

2021 ◽  
pp. 3323-3335
Author(s):  
Mustafa M. Kadhim ◽  
Layla A. Al. Juber ◽  
Ahmed S. M. Al-Janabi
Keyword(s):  
Electron Density ◽  
Density Functional ◽  
Room Temperature ◽  
Theoretical Study ◽  
Energy Gap ◽  
Basis Set ◽  
Total Electron Density ◽  
Functional Theory ◽  
Total Electron ◽  
Homo Lumo

    Seven Zn-dithiocarbamate complexes were suggested as corrosion inhibitors. Density functional theory (DFT) was used to predict the ability of inhibition. Room temperature conditions were applied to suggest the optimization of complexes, physical properties, and corrosion parameters. In addition, the HOMO, LUMO, dipole moment, energy gap, and other parameters were used to compare the inhibitors efficiency. Gaussian 09 software with LanL2DZ basis set was used. Total electron density (TED) and electrostatic surface potential (ESP) were utilized to show the sites of adsorption according to electron density.

scholarly journals Theoretical Study of Oxygen Atom Adsorption on A Polycyclic Aromatic Hydrocarbon Using Density-Functional Theory

2021 ◽  
Vol 21 (5) ◽  
pp. 1072
Author(s):  
Mokhammad Fajar Pradipta ◽  
Harno Dwi Pranowo ◽  
Viny Alfiyah ◽  
Aulia Sukma Hutama
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Singlet State ◽  
Energy Profile ◽  
Bridge Site ◽  
Functional Theory ◽  
Energy Profiles ◽  
Polycyclic Aromatic ◽  
Plausible Mechanism

Potential energy curves (PECs) and energy profiles of atomic O attack on coronene as a model for graphene/graphitic surface and interstellar reaction surface have been computed at the unrestricted B3LYP/cc-pVDZ level of theory to elaborate on atomic O attack mechanism and chemisorption on coronene. The PECs were generated by scanning the O atom distance to the closest carbon atom on "top" and "bridge" positions in the coronene, while fully relaxed geometries in the triplet state were investigated to gain the energy profile. We found that the most favorable geometry as the final product was the chemically bound O on the "bridge" site in the singlet state with an interaction energy of –29.2 kcal/mol. We recommended a plausible mechanism of atomic O attack and chemisorption reaction on coronene or generally graphitic surface starting from the non-interacting O atom and coronene systems into the chemically bound O atom on coronene.

scholarly journals Theoretical Study of the Electronic Spectrum of Disulfur Monoxide

2014 ◽  
Vol 69 (5-6) ◽  
pp. 215-219 ◽  
Author(s):  
Carlos J. Cobos ◽  
Adela E. Croce
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Basis Set ◽  
Visible Absorption ◽  
Functional Theory ◽  
Near Ultraviolet ◽  
Td Dft ◽  
Electronically Excited ◽  
First Time ◽  
Analytical Expressions

The near ultraviolet-visible absorption spectrum of disulfur monoxide ( S2O) has been theoretically studied by using the time-dependent density functional theory (TD-DFT) and the equation of motion coupled-cluster singles and doubles approach (EOM-CCSD) combined with the AUG-cc-PVQZ basis set. From this, analytical expressions for the absorption coefficient over the 250 - 340 nm range are reported for the first time. The computed molecular structure and the vibrational frequencies for the ground and third electronically excited state S2O (C 1Aʹ), responsible of the observed spectrum, are compared with available data.

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