A Computational Study of Methyl α-D-Arabinofuranoside:  Effect of Ring Conformation on Structural Parameters and Energy Profile

1999 ◽  
Vol 121 (41) ◽  
pp. 9682-9692 ◽  
Author(s):  
Matthew T. Gordon ◽  
Todd L. Lowary ◽  
Christopher M. Hadad
Keyword(s):  
Computational Study ◽  
Structural Parameters ◽  
Energy Profile ◽  
Ring Conformation

A Computational Study of the Conformational Behavior of 2,5-Dimethyl- 1,4-dithiane-2,5-diol and Analogous S and Se: DFT and NBO Study

2020 ◽  
Vol 17 (10) ◽  
pp. 749-759
Author(s):  
Elmira Danaie ◽  
Shiva Masoudi ◽  
Nasrin Masnabadi
Keyword(s):  
Thermodynamic Parameters ◽  
Computational Study ◽  
Structural Parameters ◽  
Nbo Analysis ◽  
Electron Delocalization ◽  
Stereoelectronic Effects ◽  
Conformational Properties ◽  
Molecular Reactivity ◽  
Stabilization Energies ◽  
The Stability

Conformational behaviors of 2,5-dimethyl-1,4-dithiane-2,5-diol (compound 1), 2,5- dimethyl-1,4-dithiane-2,5-dithiol (compound 2) and 2,5-dimethyl-1,4-dithiane-2,5-diselenol (compound 3) were investigated by the B3LYP/6-311+G **, the M06-2X/aug-ccpvdz levels of theory and natural bond orbital NBO analysis. The structures and the structural parameters of the mentioned molecules were optimized by the B3LYP and the M06-2X methods. We assessed the roles and contributions of the effective factors in the conformational properties of the mentioned compounds by means of the B3LYP and M06-2X levels of theory and the NBO interpretations. The stereoelectronic effects of the mentioned molecules were studied using the NBO analysis. The results showed that the stereoelectronic effects were in favor of the (ax,ax) conformers (the most stable conformations), from compound 1 to compound 3; therefore, these effects have impacts on the conformational properties of compounds 1-3, and stabilization energies associated with LP2X→ σ*S1-C2 electron delocalization, where [X= O, S, and Se], for 1-ax, ax conformer has the greatest value between all of the other conformers. Therefore, according to the calculated thermodynamic parameters, the stability of the 1-ax, ax compound was justified by the presence of LP2X→σ*S1-C2 electron delocalization. A molecular orbital explanation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the molecular reactivity parameters. There is a direct relationship between the stereoelectronic effects, molecular reactivity and thermodynamic parameters of compounds 1 to 3 as the harder ax, ax conformations with the greater stereoelectronic effects and ΔG(eq-ax) values are more stable than their corresponding eq, eq conformers. Besides frontier molecular orbitals (FMOs), mapped molecular electrostatic potential (MEP) surfaces of conformations of compounds 1 to 3 were investigated.

A Computational Study of the Translational Motion of Protons in Zeolite H-ZSM-5

2000 ◽  
Vol 658 ◽  
Author(s):  
M.E. Franke ◽  
M. Sierka ◽  
J. Sauer ◽  
U. Simon
Keyword(s):  
Activation Energy ◽  
Quantum Mechanics ◽  
Potential Energy ◽  
Interatomic Potential ◽  
Computational Study ◽  
Translational Motion ◽  
Energy Profile ◽  
Potential Energy Profile ◽  
Transition Structures ◽  
Deprotonation Energy

ABSTRACTThe potential energy profile for proton translational motions between two neighboring Alsites in zeolite H-ZSM-5 is calculated by a combined quantum mechanics-interatomic potential function approach. Thepotential energies of the six stable intermediate proton positions and the five transition structures along this path show an almost symmetrical trend reaching the maximum in the middle between these sites. Therefore, the maximum barrier will decrease with decreasing SiO2/Al2O3 ratio of thezeolite. For the SiO2/Al2O3 ratio examined (190) an activation energy of∼ 210 kJ/mol is calculated. This is much lower than the energy of deprotonation, about 1300 kJ/mol. The deprotonation energy of an Al-OH-Si bridge is obviously partially compensated by the proton affinity of the Si-O-Si bridges.

scholarly journals Study on structural, mechanical, electronic, vibrational, optical and thermo-dynamical behaviour of ZB Structured BeZ (Z=S, Se and Te) using ATK-DFT

10.30544/475 ◽  
2020 ◽  
Vol 26 (3) ◽  
pp. 253-278
Author(s):  
KRISHNA KUMAR MISHRA
Keyword(s):  
Band Structure ◽  
Material Properties ◽  
Local Density ◽  
Computational Study ◽  
Structural Parameters ◽  
Dft Method ◽  
Electronic Energy ◽  
Dynamical Behaviour ◽  
Generalized Gradient ◽  
Beryllium Chalcogenides

The present research is a systematic computational study focused on structural, mechanical, electronic, vibrational, optical and thermo-dynamical properties of zinc-blende (B3) structured beryllium chalcogenides BeZ (Z=S, Se, Te) compounds using ATK-DFT method using PZ and PBEsol exchange and correlation potentials within the local density approximation (LDA) and the generalized gradient approximation (GGA) respectively and their comparison. The k-point and energy cut-off values were tested and provided convergence in self-consistent calculations. The structural parameters such as lattice constant, bulk modulus, second order elastic constants (C11, C12, C44) and material properties (B, G, Y and σ) for these crystals are computed and discussed. To explain the electronic properties, electronic energy band structure, complex band structures, phonon band structure, phonon density of state and electron density distribution are plotted. The effect of pressure on elastic constant, material properties and phase transitions are also studied, including phase transition from ZB structure to NiAs appearing at 53 GPa, 49 GPa and 33 GPa for BeS, BeSe, and BeTe respectively.

Structure and bonding of 2,2,2-trichloroethylacetate: An experimental gas phase and computational study

2016 ◽  
Vol 71 (12) ◽  
pp. 1253-1260 ◽  
Author(s):  
Sebastian Blomeyer ◽  
Christian G. Reuter ◽  
Diego M. Gil ◽  
María E. Tuttolomondo ◽  
Aída Ben Altabef ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Density Functional ◽  
Dynamic Models ◽  
Computational Study ◽  
Structural Parameters ◽  
Interacting Quantum Atoms ◽  
The One ◽  
Gas Phase Structure

AbstractThe structural and conformational properties of 2,2,2-trichloroethylacetate, H3CCO2CH2CCl3, have been determined in the gas phase using gas electron diffraction (GED). The experimental measurements were complemented by MP2 and DFT quantum-chemical calculations. Two conformers separated by a shallow rotational barrier have been identified, one of C1 (syn-gauche) and the other of Cs symmetry (syn-anti). All calculations indicate that syn-gauche is preferred in terms of enthalpy, whereas syn-anti seems to be slightly more stable regarding Gibbs free energy. In the gas-phase structure determination, dynamic models based on different potential energy surface scans were used. The one from dispersion-corrected density functional theory, predicting a preference of syn-gauche by 1.7kJmol−1, was found to describe the experimental data best. One- and two-conformer models had to be rejected due to correlations and unrealistically large amplitudes. Experimentally determined structural parameters are in good agreement with both, quantum-chemical calculations as well as GED data for related compounds. Interacting quantum atoms (IQA) analyses revealed that interplay between the carbonyl group and the hydrogen as well as chlorine atoms of the trichloroethyl group accounts for most of the stabilisation of the C1 conformer. With intramolecular symmetry-adapted perturbation theory (I-SAPT) analyses it was possible to further elucidate the nature of dominant interactions in the two conformers. Herein, preference of syn-gauche can for the most part be attributed to electrostatic and to some extent to induction and dispersion interplays. In contrast this conformer is severely destabilised through steric repulsion. These results were supported by NBO analyses.

scholarly journals Computational study of the neutron flux produced by the 2H(d,n)3He reaction

2019 ◽  
Vol 23 ◽  
pp. 143
Author(s):  
G. Marangouli ◽  
M. Kokkoris ◽  
A. Lagoyannis ◽  
N. Patronis ◽  
R. Vlastou ◽  
...  
Keyword(s):  
Experimental Data ◽  
Neutron Flux ◽  
Cross Section ◽  
Neutron Fluence ◽  
Computational Study ◽  
Reaction Rates ◽  
Energy Profile ◽  
Experimental Conditions ◽  
Simulation Code ◽  
Fission Fragments

Quasi-monoenergetic neutron beams, in the energy range of 4-10 MeV produced via the 2H(d,n)3He reaction, have been used for cross section measurements at the 5.5 MeV tandem T11/25 Accelerator Laboratory of NCSR “Demokritos”. For accurate cross section measurements, it is important that the energy profile of the neutron beam and the experimental conditions are well characterized. Therefore, an investigation of the energy dependence of the neutron fluence, especially taking into account the deuteron break up phenomenon, has been carried out in the present work, using the recently developed analytical and Monte-Carlo simulation code NeusDesc. Fission experimental data from 238U ultra-thin targets, were used to validate the simulated results. The fission fragments of the 238U(n,f) reaction have been detected via MicroMegas detectors and using the well known cross section of the 238U isotope, the neutron flux has been deduced. The simulated reaction rates were in good aggrement with the experiment ones, thus confirming the validity of the simulations.

scholarly journals Inhibition of API 5L X52 Pipeline Steel Corrosion in Acidic Medium by Gemini Surfactants: Electrochemical Evaluation and Computational Study

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Ibrahim Hamed ◽  
Magda Mohamed Osman ◽  
Omnia Hassan Abdelraheem ◽  
Maher Ibrahim Nessim ◽  
Maryam Galal El mahgary
Keyword(s):  
Corrosion Inhibitors ◽  
Inhibition Efficiency ◽  
Gemini Surfactants ◽  
Energy Gap ◽  
Electrochemical Impedance ◽  
Computational Study ◽  
Pipeline Steel ◽  
Structural Parameters ◽  
Theoretical Evaluation ◽  
Chemical Structures

The efficiency of three new synthesized Gemini surfactants (namely, A312, A314, and A316) of the type 4,4-[1,4phenylenebis(azanylylidene)bis(N,N-dimethyl-N-alkylaminium] bromide is evaluated as corrosion inhibitors for carbon steel API 5L X52 grade in 1M HCl. The relation between the experimental inhibition efficiency and theoretical chemical parameters obtained by computational calculation in order to predict the behavior of the organic compounds as corrosion inhibitors was instigated. The chemical structures were elucidated using1HNMR spectra. Inhibition performance was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and weight loss tests. The polarization curves show that applied surfactants act as mixed type inhibitors. Nyquist plots showed the semicircle capacitive loop with different surfactants and concentrations. The inhibition efficiency orders are A312 > A314 > A316 with the highest efficiency of 94.87% for A312. Adsorption of inhibitors on API X52 steel surface was found to obey Langmuir isotherm. Theoretical evaluation of the inhibitory effect was performed by computational quantum chemical calculations. The molecule structural parameters (EHOMO), (ELUMO), energy gap (ΔE), and the dipole moment (μ) were determined. The results of experimental inhibition efficiency and theoretical calculated quantum parameters were subjected to correlation analysis.

scholarly journals Novel Dihydro-1,3,2H-benzoxazine Derived from Furfurylamine: Crystal Structure, Hirshfeld Surface Analysis, Photophysical Property, and Computational Study

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 568
Author(s):  
Worawat Wattanathana ◽  
Yuranan Hanlumyuang ◽  
Suttipong Wannapaiboon ◽  
Kantapat Chansaenpak ◽  
Piyanut Pinyou ◽  
...  
Keyword(s):  
Computational Study ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Photophysical Properties ◽  
Chair Conformation ◽  
Structural Features ◽  
Vital Role ◽  
One Pot ◽  
Td Dft ◽  
Oxazine Ring

Dihydro-1,3,2H-benzoxazines (or benzoxazine monomers) are a class of compounds that have been widely utilized in many areas such as the production of the functional polymers and optoelectronic materials. The structure variety of the benzoxazines plays a vital role in their desired properties. The effort of synthesizing functionalized benzoxazines from bioresources is of interest for sustainable development. Herein, we report the synthesis of the novel benzoxazine monomer referred to as 3-(furan-2-ylmethyl)-6-methyl-3,4-dihydro-2H-benzo[e][1,3]oxazine or benzoxazine (I) from a one-pot Mannich reaction using p-cresol, paraformaldehyde, and furfurylamine (a bio-derived amine). An X-ray crystallographic study was performed at low temperature (100 K) to obtain the structural characteristics of the benzoxazine (I). The result reveals that the oxazine ring adopts a half chair conformation to locate all the members of the benzoxazine ring as planar as possible by employing the expansion of the bond angles within the ring. Apart from the structural parameters, the intermolecular interactions were also examined. It was found that the significant interactions within the crystal are C–H···N, C–H···O, and the C–H···π interactions. The C–H···N interactions link the benzoxazine (I) molecules into an infinite molecular chain, propagating along the [100] direction. Hirshfeld surfaces and their corresponding fingerprint plots were comprehensively analyzed to confirm and quantify the significance of these interactions. Moreover, the photophysical properties of the benzoxazine (I) were investigated in solvents with various polarities. The corresponding relations between the structural features, frontier molecular orbitals, and absorption-and-emission characteristics were proposed and explained according to the DFT and TD-DFT calculations.

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