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Dichloro‐diphenyl‐trichloroethane (DDT) analogs, classified as environmental endocrine disrupting compounds (EDCs), have been extensively employed as potent insecticides that can cause endocrine system disruption. However, the precise dynamic structural characteristics and interactions between human estrogen‐related receptor gamma (hERRγ) and DDT analogs are not yet fully understood. In this study, we comprehensively investigate the impact of these EDCs (DDT, dichloro‐diphenyl‐dichloroethane (DDD), 2,2‐bis(4‐chlorophenyl)ethanol (DDOH), O,P′‐DDT (2,4′‐DDT), 4,4′‐dichlorobenzophenone (DCBP), and 4‐hydrotamoxifen (4‐OHT) on the structural changes of hERRγ and their interaction mechanisms by employing multiple molecular dynamics (MD) simulations coupled with MM‐PBSA and SIE approaches. The consequence manifested that overall structures of these six complexes did not transform markedly, but these compounds can affect the local hERRγ structure, leading to essential changes in interactions with pivotal residues nearby L268, V313, L309, Y326, and F435. And van der Waals interactions are the key to how these EDCs interact with hERRγ. These outcomes contribute to our comprehension the risks of DDT analogues to human health. [ABSTRACT FROM AUTHOR]

An in-depth theoretical study is carried out at the B3LYP/6-311G(d,p), M062X/aug- cc-pVDZ and CCSD(T)/6-311++G(3df,2dp) (single-point) levels as an attempt to explore the mechanism of the little-understood ion-molecule reaction between NH+ and CH2O. Various possible reaction pathways are taken into account. It is shown that six dissociation products, including P 1 (2N + CH2OH+), P 2 (4N + CH2OH+), P 3 (3NH + CH2O+), P 4 (NH2 + HCO+), P 5 (NH [ABSTRACT FROM AUTHOR]

The reaction of C2(A3Π u) with CH4 has been investigated over a wide temperature range 200-3,000 K by direct ab initio dynamics method at the BMC-CCSD//BB1K/6-311+G(2d,2p) level of theory. The optimized geometries and frequencies of the stationary points are calculated at the BB1K/6-311+G(2d,2p) level, and then the energy profiles of the reactions are refined using the BMC-CCSD method. The activation barrier height for H-abstraction reaction was calculated to be 4.44 kcal/mol in temperature range (337-605 K), and the electron transfer behavior was also analyzed by quasi-restricted molecular orbital method in detail. The canonical variational transition-state theory (CVT) with the small curvature tunneling (SCT) correction method is used to calculate the rate constants over a wide temperature range 200-3,000 K. The theoretical results shows that variational effect is to some extent large in lower temperature range, and small curvature and tunneling effect play important roles to the H-atom abstraction only at lower temperatures. The CVT/SCT rate constants are in good agreement with the available experimental results. Our theoretical study is expected to provide a direct insight into the reaction mechanism and may be useful for estimating the kinetics of the title reaction over a wide temperature range where no experimental data are available so far. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 [ABSTRACT FROM AUTHOR]

The reaction of C2(A3Π u) with CH4 has been investigated over a wide temperature range 200-3,000 K by direct ab initio dynamics method at the BMC-CCSD//BB1K/6-311+G(2d,2p) level of theory. The optimized geometries and frequencies of the stationary points are calculated at the BB1K/6-311+G(2d,2p) level, and then the energy profiles of the reactions are refined using the BMC-CCSD method. The activation barrier height for H-abstraction reaction was calculated to be 4.44 kcal/mol in temperature range (337-605 K), and the electron transfer behavior was also analyzed by quasi-restricted molecular orbital method in detail. The canonical variational transition-state theory (CVT) with the small curvature tunneling (SCT) correction method is used to calculate the rate constants over a wide temperature range 200-3,000 K. The theoretical results shows that variational effect is to some extent large in lower temperature range, and small curvature and tunneling effect play important roles to the H-atom abstraction only at lower temperatures. The CVT/SCT rate constants are in good agreement with the available experimental results. Our theoretical study is expected to provide a direct insight into the reaction mechanism and may be useful for estimating the kinetics of the title reaction over a wide temperature range where no experimental data are available so far. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 [ABSTRACT FROM AUTHOR]

At various levels of theory, singlet and triplet potential energy surfaces (PESs) of Si2CO, which has been studied using matrix isolation infrared spectroscopy, are investigated in detail. A total of 30 isomers and 38 interconversion transition states are obtained at the B3LYP/6-311G(d) level. At the higher CCSD(T)/6-311+G(2d)//QCISD/6-311G(2d)+ZPVE level, the global minimum 11 (0.0 kcal/mol) corresponds to a three-membered ring singlet O-cCSiSi (1A′). On the singlet PES, the species 12 (0.2 kcal/mol) is a bent SiCSiO structure with a 1A′ electronic state, followed by a three-membered ring isomer Si-cCSiO (1A′) 13 (23.1 kcal/mol) and a linear SiCOSi 14 (1Σ+) (38.6 kcal/mol). The isomers 11, 12, 13, and 14 possess not only high thermodynamic stabilities, but also high kinetic stabilities. On the triplet PES, two isomers 31 (3B2) (18.8 kcal/mol) and 37 (3A″) (23.3 kcal/mol) also have high thermodynamic and kinetic stabilities. The bonding natures of the relevant species are analyzed. The similarities and differences between C3O, C3S, SiC2O, and SiC2S are discussed. The present results are also expected to be useful for understanding the initial growing step of the CO-doped Si vaporization processes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

The reaction of N (2D) radical with NO2 molecule has been studied theoretically using density functional theory and ab initio quantum chemistry method. Singlet electronic state [N2O2] potential energy surfaces (PES) are calculated at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311+G(d) + ZPE and G3B3 levels of theory. All the involved transition states for generation of (2NO) and (O2 + N2) lie much lower than the reactants. Thus, the novel reaction N + NO2 can proceed effectively even at low temperatures and it is expected to play a role in both combustion and interstellar processes. On the basis of the analysis of the kinetics of all pathways through which the reactions proceed, we expect that the competitive power of reaction pathways may vary with experimental conditions for the title reaction. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]

The structures, spectroscopies, and stabilities of the doublet Si2NO radical are explored at the density functional theory (DFT) and ab initio levels. Seventeen isomers are located, connected by 26 interconversion transition states. At the CCSD(T)/6-311+G(2df)//QCISD/6-311G(d)+ZPVE level, three low-lying isomers are predicted, that is, one bent species SiNSiO 3 (5.1 kcal/mol) containing the important Si&tbond;N triple bonding and two four-membered ring isomers including cyclic cSiNSiO 1 (0.0) with Si&bond;Si cross-bonding with C2v symmetry and puckered cSiNSiO 1′ (11.9) with divalent carbene character. Three low-lying isomers 1, 1′, and 3 have reasonable kinetic stabilities and might be observable either experimentally or astrophysically. The possible formation strategies of 1, 1′, and 3 in laboratory and in space are discussed in detail. The calculated vibrational frequencies and possible formation processes of 3 are consistent with recent experimental observations. In light of the fact that no cyclic nitrogen-containing species have been detected in space, two cyclic isomers 1 and 1′ could be promising candidates. Furthermore, the bonding nature of three isomers 1, 1′, and 3 is analyzed. The calculated results are also compared with those of the analogue C2NO radical. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]