scholarly journals Quantum Chemical Study on the Influence of Dodecyl Trimethyl Ammonium Bromide on the CH4 Adsorption of Coal

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 894
Author(s):  
Shuo Liu ◽  
Jiaxing Gao ◽  
Yibo Tang ◽  
Junfeng Wang ◽  
Shaocheng Ge
Keyword(s):  
Adsorption Capacity ◽  
Density Functional ◽  
Molecular Model ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Ammonium Bromide ◽  
Microscopic Mechanism ◽  
Ch4 Adsorption ◽  
Dodecyl Trimethyl Ammonium Bromide ◽  
Adsorption Energies

The adsorption of dodecyl trimethyl ammonium bromide (DTAB) on coal can affect the wettability of coal and change the water absorption of coal. After DTAB treatment, the change in the CH4 adsorption capacity of coal is worth further study. To reveal the microscopic mechanism of the influence of DTAB on the CH4 adsorption capacity of coal, we employed the density functional theory (DFT) with the 6-311 G (d, p) basis set. DFT-based computations interpreted the adsorption process of CH4 and DTAB on coal molecules and determined the stable structure, adsorption distance, Mulliken overlapping populations, and adsorption energies of the two adsorption configurations. The results showed that the adsorption energies of CH4 and DTAB on the molecular model of coal were 2.15 and 42.69 kJ/mol and the adsorption stability distances were 0.261 and 0.238 nm, respectively. The DTAB–coal configuration was more stable than the CH4–coal configuration. When there was competitive adsorption between DTAB and CH4 on coal, the coal molecules preferentially adsorb the DTAB. Infrared spectroscopy and adsorption experiments were also carried out, and the calculation results of quantum chemistry are consistent with the experimental results.

Quantum chemical study on the atmospheric photooxidation of ethyl acetate

2014 ◽  
Vol 92 (9) ◽  
pp. 814-820 ◽  
Author(s):  
Yan Zhao ◽  
Xiaomin Sun ◽  
Wenxing Wang ◽  
Laixiang Xu
Keyword(s):  
Acetic Anhydride ◽  
Ethyl Acetate ◽  
Density Functional ◽  
Single Point ◽  
Quantum Chemical Study ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Oh Radicals ◽  
Point Energy ◽  
Rearrangement Reaction

The mechanism for OH radical initiated atmospheric photoxidation reaction of ethyl acetate was carried out by using the density functional theory method. Geometries have been optimized at the B3LYP level with a standard 6-31G(d,p) basis set. The single-point energy calculations have been performed at the MP2/6-31G(d), MP2/6-311++G(d,p), and CCSD(T)/6-31G(d) levels, respectively. All of the possible degradation channels involved in the oxidation of ethyl acetate by OH radicals have been presented and discussed. Among the five possible hydrogen abstraction pathways of the reaction of ethyl acetate with OH radicals, the hydrogen abstractions from the C1–H3 and C2–H5 bonds are the dominant reaction pathways due to the low potential barriers and strong exothermicity. The β-ester rearrangement of IM6 is energetically favorable but is not expected to be important. The α-ester rearrangement reaction and O2 direct abstraction from IM17 are the more favorable pathways and are strongly competitive. In addition, the α-ester rearrangement reaction is confirmed to be a one-step process. Acetic acid, formic acetic anhydride, acetoxyacetaldehyde, and acetic anhydride are the main products for the reaction of ethyl acetate with OH radicals.

Study on Pyrrole 4-Pyrazoline Derivatives: Experimental and Quantum Chemical Approaches

2016 ◽  
Vol 69 (6) ◽  
pp. 672 ◽  
Author(s):  
R. N. Singh ◽  
Poonam Rawat ◽  
Vikas Baboo
Keyword(s):  
Dft Calculations ◽  
13C Nmr ◽  
Quantum Chemical ◽  
Density Functional ◽  
Electronic Absorption Spectra ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Dft Methods ◽  
Pyrrole Derivatives ◽  
1H And 13C Nmr

As part of a study on pyrrole derivatives we report here a combined experimental and quantum chemical study of pyrrole 4-pyrazoline biheterocyclic derivatives. The structure of the synthesised compounds have been studied using experimental IR, UV, 1H and 13C NMR spectroscopic analyses along with density functional theory (DFT) calculations using the B3LYP functional with 6–311+G (d,p) basis set. The global, local reactivity, and thermodynamic parameters support the analysis. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. In addition, the computed 1H and 13C NMR data, obtained by DFT calculations, are found to be in good agreement with the experimental data and serve as valuable tools in identifying the products. The vibrational analysis shows red shifts in vN–H and vC=O stretching vibrations as a result of dimer formation. The theoretical electronic absorption spectra have been calculated by using time dependent-DFT methods. The static first hyperpolarizability (β0) values for the synthesized pyrrole–pyrazoline derivatives 4A–D are calculated as 16.97 × 10–30, 47.64 × 10–30, 65.40 × 10–30, 65.39 × 10–30 esu, respectively, and increase from 4A to 4C as a result of the addition of an –NO2 acceptor in 4B and two –NO2 group acceptors in 4C. However, an additional –Cl group in 4D on the phenyl ring attached to the pyrazoline moiety does not result in a clear change from 4C. The calculated static and dynamic hyperpolarizability results show that the investigated molecules might be used as non-linear optical materials.

Studies of intramolecular H-bond interactions and solvent effects in the conformers of glycolic acid — A quantum chemical study

2018 ◽  
Vol 17 (01) ◽  
pp. 1850009 ◽  
Author(s):  
Mahendiraprabu Ganesan ◽  
Nirmala Vedamanickam ◽  
Selvarengan Paranthaman
Keyword(s):  
Solvent Effects ◽  
Density Functional ◽  
Glycolic Acid ◽  
Chemical Potential ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Basis Set ◽  
Chemical Hardness ◽  
Geometrical Parameters ◽  
Water Media

In this work, density functional theory is applied to understand the conformational stability and solvent effects on glycolic acid conformers in different solvents. In addition, the role of intramolecular hydrogen bond (H-bond) interactions in the stability of conformers are investigated. The molecular geometries of selected conformers are optimized using B3LYP and PBE0 functionals with 6-311[Formula: see text]G(d,p) basis set. The effects of solvent on the geometrical parameters, relative stability, dipole moment, chemical hardness, chemical potential, etc. are studied for the conformers of glycolic acid. Our calculations show that the order of stability of the SSC and AAT conformers does not change in liquid phase. However, the energy of SSC and AAT conformers is very close to each other in water media. In water media, strong intramolecular H-bond interaction is present in AAT conformer which causes the energy of AAT conformer to be very close to that of SSC conformer. This may be due to the influence of water media.

scholarly journals Quantum chemical modeling of the structure and properties of SnO2 nanoclusters

2021 ◽  
Vol 12 (4) ◽  
pp. 283-290
Author(s):  
O. V. Filonenko ◽  
◽  
A. G. Grebenyuk ◽  
V. V. Lobanov ◽  
◽  
...  
Keyword(s):  
Bond Length ◽  
Cluster Size ◽  
Density Functional ◽  
Tin Dioxide ◽  
Energy Gap ◽  
Molecular Model ◽  
Basis Set ◽  
Atomization Energy ◽  
Hydroxyl Groups ◽  
Energy Characteristics

By the method of density functional theory with exchange-correlation functional B3LYP and basis set 3‑21G (d), the structural and energy characteristics have been considered of the molecular models of SnO2 nanoclusters of different size and composition with the number of Sn atoms from 1 to 10. Incompletely coordinated surface tin atoms were terminated by hydroxyl groups. It has been shown that the Sn–O bond length in nanoclusters does not depend on the cluster size and on the coordination number of Sn atoms, but is determined by the coordination type of neighboring oxygen atoms. Namely, the bond length Sn–O(3) (@ 2.10 Å) is greater than that of Sn–O (2) (@ 1.98 Å). The calculated values of Sn–O (3) bond lengths agree well with the experimental ones for crystalline SnO 2 samples (2.05 Å). The theoretically calculated width of the energy gap decreases naturally with increasing cluster size (from 6.14 to 3.46 eV) and approaches the experimental value of the band gap of the SnO 2 crystal (3.6 eV). The principle of additivity was used to analyze the energy characteristics of the considered models and to estimate the corresponding values for a cassiterite crystal. According to this principle, a molecular model can be represented as a set of atoms or atomic groups of several types that differ in the coordination environment and, therefore, make different contributions to the total energy of the system. The calculated value of the atomization energy for SnO2 is 1661 kJ/mol and corresponds satisfactorily to the experimentally measured specific atomization energy of crystalline SnO2 (1381 kJ/mol). It has been shown that a satisfactory reproduction of the experimental characteristics of crystalline tin dioxide is possible when using clusters containing at least 10 state atoms, for example, (SnO2)10×14H2O.

scholarly journals Quantum-Chemical Study on the Relative Stability of Sildenafil Tautomers

2021 ◽  
Author(s):  
Wojciech Piotr Oziminski ◽  
Igor Wiśniewski
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Water Solution ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Steric Interaction ◽  
Free Energies ◽  
Dft Methods ◽  
Enol Tautomer ◽  
Tautomeric Mixture

Abstract The tautomeric equilibrium of Sildenafil molecule was theoretically studied using B3LYP and M06-2X Density Functional Theory (DFT) methods in connection with aug-cc-pVDZ correlation consistent basis set. Calculations were performed for gas phase and water solution conditions modelled by Polarizable Continuum Model (PCM). Three tautomeric forms are possible. Two keto forms: A – where the tautomeric proton in more distant from carbonyl group, B – where it is closer, and one enol form denoted C. Both DFT methods qualitatively give similar tautomer stability order: B>A>C. The B tautomer is dominant in gas phase and water environment, whereas the C tautomer is too high in energy to be present in the tautomeric mixture. Regarding the A tautomer, it is not present in the gas phase but is present in small amounts in water solution. According to B3LYP/ aug-cc-pVDZ the relative Gibbs free energies for A and C relative to B, are 10.05 kcal/mol and 11.91 kcal/mol for gas phase and 5.49 kcal/mol and 12.49 kcal/mol for water solution. According to M06-2X/aug-cc-pVDZ the relative Gibbs free energies for A and C are 9.12 kcal/mol and 10.60 kcal/mol for gas phase and 4.27 kcal/mol and 10.23 kcal/mol for water solution. Therefore, for in vivo conditions we expect that the B tautomer is dominant and there may exist small amounts of the A tautomer. The C enol tautomer is not present at all. This picture is very different from the parent tautomeric system: 4-hydroxypyrimidine/4-pyrimidinone where the C enol tautomer is less stable than keto B only by about 1 kcal/mol in the gas phase and the A keto tautomer is the least stable and not present in the tautomeric mixture. In order to understand these differences we performed additional calculations for series of parent molecules starting from 4-hydroxypyrimidine/4-pyrimidinone, going through two in-between model molecules and ending at Sildenafil molecule. We found that the most important reasons of C form destabilization are: dearomatization of the 6-membered ring caused by the fusion with pyrazole ring, lack of strong intramolecular hydrogen bond in C form of Sildenafill and presence of destabilizing steric interaction of oxygen and nitrogen atoms of two 6-memberd rings in this tautomer.

Efficient Synthesis, Spectroscopic and Quantum Chemical Study of 2,3-Dihydrobenzofuran Labelled Two Novel Arylidene Indanones: A Comparative Theoretical Exploration

2020 ◽  
Vol 17 (2) ◽  
pp. 146-161
Author(s):  
Rahul Ashok Shinde ◽  
Vishnu Ashok Adole ◽  
Bapu Sonu Jagdale ◽  
Thansing Bhavsing Pawar ◽  
Bhatu Shivaji Desale
Keyword(s):  
Magnetic Resonance ◽  
Density Functional ◽  
Computational Study ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Basis Set ◽  
Frontier Molecular Orbital ◽  
Reactivity Descriptors ◽  
B3lyp Method ◽  
The Density Functional Theory

Indanone and 2,3-dihydrobenzofuran scaffolds are considered as special structures in therapeutic science and explicitly associated with various biologically potent compounds. In the present disclosure, we report the synthesis of two new 2,3-dihydrobenzofuran tethered arylidene indanones via an environmentally adequate and viable protocol. The two compounds revealed in this have been characterized well by analytical methods; proton magnetic resonance (PMR), carbon magnetic resonance (CMR). The Density Functional Theory (DFT) study has been presented for the spectroscopic, structural and quantum correlation between (E)-2-((2,3-dihydrobenzofuran-5-yl)methylene)-2,3-dihydro-1H-inden-1-one (DBDI) and (E)-7-((2,3-dihydrobenzofuran-5-yl)methylene)-1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one (DBTI). Optimized geometry, frontier molecular orbital, global reactivity descriptors, and thermodynamic parameters have been computed for DBDI and DBTI. DFT/B3LYP method using basis set 6-311++G (d,p) has been employed for the computational study. Mulliken atomic charges are established by using 6-311G (d,p) basis set. Besides, molecular electrostatic potential for DBDI and DBTI is also explored to locate the electrophilic and nucleophilic centres.

scholarly journals Quantum-chemical study on the relative stability of sildenafil tautomers

2021 ◽  
Author(s):  
Wojciech Piotr Oziminski ◽  
Igor Wiśniewski
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Water Solution ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Steric Interaction ◽  
Free Energies ◽  
Dft Methods ◽  
Enol Tautomer ◽  
Tautomeric Mixture

AbstractThe tautomeric equilibrium of sildenafil molecule was theoretically studied using B3LYP and M06-2X density functional theory (DFT) methods in connection with aug-cc-pVDZ correlation consistent basis set. Calculations were performed for gas phase and water solution conditions modelled by polarizable continuum model (PCM). Three tautomeric forms are possible. Two keto forms: A — where the tautomeric proton in more distant from carbonyl group and B — where it is closer, and one enol form denoted, C. Both DFT methods qualitatively give similar tautomer stability order: B > A > C. The B tautomer is dominant in gas phase and water environment, whereas the C tautomer is too high in energy to be present in the tautomeric mixture. Regarding the A tautomer, it is not present in the gas phase but is present in small amounts in water solution. According to B3LYP/aug-cc-pVDZ, the relative Gibbs-free energies for A and C relative to B are 10.05 kcal/mol and 11.91 kcal/mol for gas phase and 5.49 kcal/mol and 12.49 kcal/mol for water solution. According to M06-2X/aug-cc-pVDZ, the relative Gibbs-free energies for A and C are 9.12 kcal/mol and 10.60 kcal/mol for gas phase and 4.27 kcal/mol and 10.23 kcal/mol for water solution. Therefore, for in vivo conditions, we expect that the B tautomer is dominant, and there may exist small amounts of the A tautomer. The C enol tautomer is not present at all. This picture is very different from the parent tautomeric system: 4-hydroxypyrimidine/4-pyrimidinone where the C enol tautomer is less stable than keto B only by about 1 kcal/mol in the gas phase and the A keto tautomer is the least stable and not present in the tautomeric mixture. In order to understand these differences, we performed additional calculations for a series of parent molecules starting from 4-hydroxypyrimidine/4-pyrimidinone, going through two in-between model molecules and ending at Sildenafil molecule. We found that the most important reasons of C form destabilization are dearomatization of the 6-membered ring caused by the fusion with pyrazole ring, lack of strong intramolecular hydrogen bond in C form of sildenafil and presence of destabilizing steric interaction of oxygen and nitrogen atoms of two 6-memberd rings in this tautomer.

scholarly journals QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF BENZOELACETHYLENE WITH DITIO- AND DISELENOMALONAMIDES

2020 ◽  
Vol 2020 (1) ◽  
pp. 127-135
Author(s):  
Elena Chirkina
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Polarizable Continuum Model ◽  
Basis Set ◽  
Mechanism Of Reaction ◽  
The Density Functional Theory ◽  
Two Stages ◽  
Polarizable Continuum

A mechanism of the interaction of benzoylacetylene with dithio- and diselenomalonamides has been proposed on the basis of quantum-chemical calculations in the framework of the density functional theory using the B3LYP/6-311++G(d,p) basis set taking into account solvent effects (AcOH) within the polarizable continuum model, PCM, with inclusion of the HCl molecule in the calculated space. It is shown that the reaction involves two stages to afford heterocyclic compounds of the dithiine and diselenine type

scholarly journals Quantum-chemical study of molecular structure and relative stability of trans and cis isomers of model anilide derivatives

2017 ◽  
Vol 10 (2) ◽  
pp. 144-151
Author(s):  
Denisa Cagardová ◽  
Peter Poliak ◽  
Vladimír Lukeš
Keyword(s):  
Density Functional ◽  
Quantum Chemical Study ◽  
Theoretical Data ◽  
Chemical Study ◽  
Basis Set ◽  
Ortho Position ◽  
Hybrid Functional ◽  
Trans Conformation ◽  
Length Changes ◽  
Cis And Trans

AbstractDerivatives of anilide were studied systematically by the density functional theory (DFT) using the B3LYP hybrid functional and the 6-311+G(3df,2p) basis set. Characteristic frequencies of N-H and C=O stretching modes for cis and trans conformers distinguishing were compared with available experimental and theoretical data. Effect of substitution in ortho position and acidic residue group is discussed with respect to the bond length changes in the aromatic ring and aromaticity indexes. Energy differences between cis and trans conformations allow estimating the effect of intramolecular hydrogen bonds stabilizing the studied conformations. The trans conformation of parent formanilide is stabilized via the C(aromatic)-H∙∙∙O=C interaction with the energy of around 4 kJ・mol-1. The selected anilide series represent model compounds for drug design.

scholarly journals A quantum chemical study on the effect of titanium dioxide modification with non-metals on its spectral characteristics

2020 ◽  
Vol 11 (4) ◽  
pp. 539-546
Author(s):  
O. V. Smirnova ◽  
◽  
A. G. Grebenyuk ◽  
V. V. Lobanov ◽  
◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Quantum Chemical ◽  
Density Functional ◽  
Spectral Characteristics ◽  
Quantum Chemical Study ◽  
Visible Region ◽  
Wavelength Region ◽  
Basis Set ◽  
Oxidation States ◽  
Impurity Atoms

The experimental results obtained in the study on the possibility of sensitizing titanium dioxide (polymorphic anatase phase) to the visible region of the spectrum by doping and co-doping with impurities of non-metals in order to create effective photocatalysts for the decomposition of organic compounds have been analyzed. The presence of impurity atoms appears to result in a change in the electronic structure of the titanium dioxide matrix, in the appearance of “impurity bands” and in the narrowing of the energy gap of titanium dioxide. Such a modification is accompanied by an extension of the spectral range of sensitivity of photoactive solids to the long-wavelength region of the spectrum and, therefore, can be used to improve the catalytic properties of these materials. Spectral manifestations of carbon impurities in titanium dioxide in the form of carbide and carbonate, as well as sulfur in the forms of sulfite, sulfide, and sulfate, have been studied by the density functional theory method. A Ti14H22O39 cluster model was chosen for the titanium dioxide matrix. The calculations were carried out in the framework of the cluster approximation, using functional B3LYP and basis set 6-31G (d, p). Comparison of the results of quantum chemical calculations with the available experimental data shows that the impurity sulfur and carbon atoms in titanium dioxide, which are in different coordination states and different oxidation states, appear in different spectral ranges. This circumstance makes it possible to elucidate the structure of the samples based on the experimental spectra. A change in the coordination and oxidation states of impurity atoms leads to spectral shifts and splitting of peaks, which can reach 1.5 eV (XPS). The presence of admixtures of non-metals leads to a change in color (deepening in the case of sulfide or carbide) of the samples, appearing in the corresponding UV spectra.

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