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Nasrin Masnabadi Afshin Taghva Manesh Fatemeh Azarakhshi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1053-1063
Abstract Stereoelectronic interactions associated with the AE and also the conformational and structural properties of 1,3-oxathiane S-oxide (1), 1,3-dithiane S-oxide (2), 1,3-thiaselenane S-oxide (3), 1,3-oxaselenane Se-oxide (4), 1,3-thiaselenane Se-oxide (5), and 1,3-diselenane Se-oxide (6) were investigated using quantum mechanical methods. These compounds were fully optimized at the B3LYP/6 – 311 + G** and HF/6 – 311 + G** levels of theory. The Gibbs Free Energy, Enthalpy, and Entropy differences (i.e., ΔG, ΔH, and ΔS) between the axial and equatorial conformations were calculated at the B3LYP/6 – 311 + G** and HF/6 – 311 + G** levels of theory. The decrease of the AE is corresponding to the decreases of calculated Δ(G ax – G eq) value of the above mentioned compounds. The calculated AE values are more significant for the justification of the conformational dominances of the compounds than steric effects. In this work, the relations between the Anomeric Effects, donor and acceptor orbital energies, occupancies, structural parameters, dipole–dipole interactions, and conformational behavior of the compounds have been studied. 相似文献
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Masnabadi Nasrin Ghasemi Mohammad Hadi Beyki Mostafa Hossein Sadeghinia Mohammad 《Research on Chemical Intermediates》2017,43(3):1609-1618
Research on Chemical Intermediates - Dimerization of thiol groups to disulfide is an important transformation in chemical processes. In this study, magnetic ion exchanged Montmorillonite-k10 was... 相似文献
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Fatemeh Azarakhshi Davood Nori-Shargh Nasrin Masnabadi Hooriye Yahyaei Seiedeh Negar Mousavi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):276-293
Abstract The impacts of the generalized anomeric effect (GAE) and gauche effect (GE) associated with donor–acceptor electron delocalizations and dipole–dipole interactions on the conformational properties of 2-methoxy- (1), 2-methylthio- (2), 2-methylseleno- (3), 2-fluoro- (4), 2-chloro- (5), and 2-bromocyclohexanone oxime (6) have been studied by means of hybrid density functional theory (B3LYP/6–311+G**) and ab initio molecular orbital (HF/6–311+G**)-based methods and natural bond orbital (NBO) interpretation. Both methods used showed that the above compounds exist predominantly in the axial chair conformation and the axial conformation stability increased from 2-methoxy- (1) to 2-methylselenocyclohexanone oxime (3) and also from 2-fluoro- (4) to 2-bromocyclohexanone oxime (6). The NBO analysis showed that the GAE increases from compound 1 to compound 3 and also from compound 4 to compound 6. GE does not have significant impact on the conformational behaviors of compounds 1–6 and GAE succeeds in accounting qualitatively for the increase of the axial preferences in both series of compounds. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Table S1. Supporting Information Available. The structures optimized and thermodynamic functions of the axial and equatorial conformations of compounds 1–6. This material is available free of charge via the Internet. 相似文献
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Afshin Taghva Manesh Zabi alah Heidarnezhad Nasrin Masnabadi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(7):1175-1179
The present work provides quantitative results for the rate of unimolecular carbon-hydrogen bond fission reaction of benzene and nitro benzene at elevated temperatures up to 2000 K. The potential energy surface for each C-H (in the ortho, meta, and para sites) bond fission reaction of nitro benzene was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C-H bond fission channel is barrier less reaction, we have used variational RRKM theory to predict rate constants. By means of calculated rate constant at the different temperatures, the activation energy and exponential factor were determined. The Arrhenius expression for C-H bond fission reaction of nitro benzene on the ortho, meta and para sites are k(T) = 2.1 × 1017exp(?56575.98/T), k(T) = 2.1 × 1017exp(?57587.45/T), and k(T) = 3.3 × 1016exp(?57594.79/T) respectively. The Arrhenius expression for C-H bond fission reaction of benzene is k(T) = 2 × 1018exp(?59343.48.18/T). The effect of NO2 group, location of hydrogen atoms on the substituted benzene ring, reaction degeneracy, benzene ring resonance and tunneling effect on the rate expression have been discussed. 相似文献
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Nasrin Masnabadi Mohammad R. Thalji Huda S. Alhasan Zahra Mahmoodi Alexander V. Soldatov Gomaa A. M. Ali 《Molecules (Basel, Switzerland)》2022,27(13)
In this study, we used density functional theory (DFT) and natural bond orbital (NBO) analysis to determine the structural, electronic, reactivity, and conformational features of 2,5,5-trimethyl-1,3,2-di-heteroatom (X) phosphinane-2-sulfide derivatives (X = O (compound 1), S (compound 2), and Se (compound 3)). We discovered that the features improve dramatically at 6-31G** and B3LYP/6-311+G** levels. The level of theory for the molecular structure was optimized first, followed by the frontier molecular orbital theory development to assess molecular stability and reactivity. Molecular orbital calculations, such as the HOMO–LUMO energy gap and the mapping of molecular electrostatic potential surfaces (MEP), were performed similarly to DFT calculations. In addition, the electrostatic potential of the molecule was used to map the electron density on a surface. In addition to revealing molecules’ size and shape distribution, this study also shows the sites on the surface where molecules are most chemically reactive. 相似文献
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