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ABSTRACT: Textile dyes and dye industrial effluents are widely known for esthetic and toxicity problems. The toxicity of three direct dyes, Direct Blending Rebine (DBLL), Direct Blending Scarlet (DGLN), and Direct Blending Yellow (D3RNL), were examined by the antioxidase and lipid peroxide index. Fish (Carassius auratus) were exposed to 100mg/L test compounds or injected with 200μg/kg corresponding dyes, and then samples of liver were collected at different times (0.5, 1, 3, 5, 7, 10, 13, 17 and 22d ) for analysis of superoxide dismutase (SOD), catalase (CAT), and contents of malondialdehyde (MDA). There is an obvious difference between two poisoning conditions and results indicated injection pattern have a more sensitive response. Besides, SOD, CAT and MDA levels displayed different variation trend following the prolonged duration, implying that dye metabolism generated less toxic or more active substance. The comparison among their intensity of enzyme inhibition showed that the toxicity order is DBLL>DGLN>D3RNL. Additionally, three direct dye molecules were optimized based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent (SMD) of Selfconsistent Reaction Field Theory (SCRF) on B3LYP/LAN2BM level and the stable configurations were obtained. Wiberg bond orders were analyzed and atom in molecule (AIM) 2000 program was employed to estimate the interaction between atoms. The possible degradation pathways and toxicities were speculated based on the computations. The calculation is consistent with the experimental results and analysis. Ecotoxicology and Environmental Safety 10/2012; 86. DOI:10.1016/j.ecoenv.2012.09.023 · 2.48 Impact Factor

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ABSTRACT: Polyhydroxylated dibenzofuran (PHODF) is an important degradation product of polychlorinated dibenzofuran (PCDF). Four types of hydrogen bonds (the one between a hydroxyl and the oxygen atom in the matrix, between hydroxyls at ortho positions, between the oxygen atom of hydroxyl at position 1 and the hydrogen atom of the matrix at position 9, and between hydroxyls at positions 1 and 9) exist in PHODFs. The energies of the hydrogen bonds were ascertained by comparing the two configurational isomers as approximately 811kJmol(1), 1621kJmol(1), 58kJmol(1) and 2325kJmol(1), respectively. An experiment was designed to verify the bond energies, and the entrance geometry on main paths was studied by AIM 2000 program. The most stable in each group of configurational isomers was ascertained on the basis of evaluating the effect of hydrogen bonds. Their thermodynamic properties (standard state entropy S°, standard enthalpy Δ(f)H° and standard Gibbs energy of formation Δ(f)G°) were calculated from the combination of density functional theory (DFT) at B3LYP/6311G** level and isodesmic reactions. Octanol/water partition coefficients (logK(ow)) were calculated on line with molinspiration methodology based on group contributions. The number and position of hydroxyl substitution (N(PHOS)) can be a good indicator of these properties for all stable PHODF congeners. The configurations most likely to form are those with a hydrogen bond (Type IV). How intramolecular hydrogen bond influences ionization was also investigated and the firstorder ionization constant for each stable conformation was obtained with the selfconsistent reaction field (SCRF) method. Journal of molecular graphics & modelling 06/2012; 38C:396410. DOI:10.1016/j.jmgm.2012.05.008 · 2.02 Impact Factor

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ABSTRACT: Polyhydroxylated dibenzopdioxins (PHODDs) are important metabolic and synthetic products of polychlorinated dibenzopdioxins (PCDDs). Two types of hydrogen bonds exist in PHODD molecules: one between a hydroxyl group (HO) and an oxygen atom of the ether bond, and the other between two ortho hydroxyls of a benzene ring. By fully optimized calculation with density functional theory (DFT), their bond energies were ascertained to be approximately 914 kJ/mol and 1519 kJ/mol respectively by the comparison of standard Gibbs energy of formation (Δ(f)G(θ)) between different molecules, which was experimentally verified. The two types of hydrogen bonds affect the hydrophilicity and stability of the molecules. The torsional potential of hydroxyls and the orientation making the congener most stable were obtained. The octanolwater partition coefficients (logK(ow)s) were calculated based on the group contribution method, and the standard state entropy (S(θ)), standard enthalpy (Δ(f)H(θ)) of formation and Δ(f)G(θ) were obtained from the combination of DFT calculation and isodesmic reaction for the stable PHODD congeners. The number and position of hydroxyl substitution (N(PHOS)) were employed as descriptors to establish quantitative structureproperty relationship (QSPR) models. Although the hydrophilicity of PHODDs increases with the number of hydroxyl groups, it is impaired by the intramolecular hydrogen bonds. The logK(ow)s of PHODDs are much smaller than those of PCDDs, and the variation trend with the number of substituents is different. In addition, the relative stability order of PHODD congeners was theoretically proposed, which is quite different from that of PCDDs. Considering the ionization in water, firstorder ionization constants of PHODDs were calculated according to the results of SMD method of SelfConsistent Reaction Field Theory (SCRF), and they were influenced by the hydrogen bonds. Science of The Total Environment 11/2011; 414:40416. DOI:10.1016/j.scitotenv.2011.10.063 · 4.10 Impact Factor

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ABSTRACT: Density functional theory (DFT) calculations were performed for a series of 2,2′bi1Himidazole derivatives. The B3LYP and B3P86 functionals with 6311G∗∗ basis set were used. The heats of formation (HOFs) were predicted through designed isodesmic reactions. Calculated results show that the HOFs decrease as the –NO2 groups being replaced by –NF2, but the HOFs increase as the –NO2 groups being replaced by –N3. When the –NO2 groups are replaced by –NH2, the HOFs initially decrease then increase. As for the isomeric compounds, the HOFs decrease following the increase of the number of hydrogen bonds for the different substituent position. At B3LYP/6311G∗∗ level, the HOF of 4,4′diamino5,5′dinitro2,2′bi1Himidazole is the smallest (125.2kJ/mol), and the HOF of 4,4′,5,5′tetraazido2,2′bi1Himidazole is the largest (1608.9kJ/mol). The magnitudes of intramolecular group interactions were predicted through the disproportionation energies. The Edisproportion of 4,4′diamino5,5′dinitro2,2′bi1Himidazole is −70.3kJ/mol and is the smallest among the title compounds, but that of 4,4′,5,5′tetranitro2,2′bi1Himidazole is the largest, which is 128.1kJ/mol. Thermal stabilities were evaluated via bond dissociation energies (BDE) at the UB3LYP/6311G∗∗ level. The BDEZPE value for C–NO2 bond, 270.0kJ/mol in average, is the smallest compared to other types of bonds. Journal of Molecular Structure THEOCHEM 08/2009; 907(1):2934. DOI:10.1016/j.theochem.2009.04.012 · 1.37 Impact Factor

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ABSTRACT: We investigated the heat of formation (ΔfH) of polynitrocubanes using density functional theory B3LYP and HF methods with 631G*, 6311+G**, and ccpVDZ basis sets. The results indicate that ΔfH firstly decreases (nitro number m=0–2) and then increases (m=4–8) with each additional nitro group being introduced to the cubane skeleton. ΔfH of octanitrocubane is predicted to be 808.08 kJ mol−1 at the B3LYP/6311+G** level. The Gibbs free energy of formation (ΔfG) increases by about 40–60 kJ mol−1 with each nitro group being added to the cubane when the substituent number is fewer than 4, then ΔfG increases by about 100–110 kJ mol−1 with each additional group being attached to the cubic skeleton. Both the detonation velocity and the pressure for polynitrocubanes increase as the number of substituents increases. Detonation velocity and pressure of octanitrocubane are substantially larger than the famous widely used explosive cyclotetramethylenetetranitramine (HMX). Propellants Explosives Pyrotechnics 04/2009; 34(2):106  109. DOI:10.1002/prep.200800007 · 1.50 Impact Factor

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ABSTRACT: By fusing four HMX rings into a cage, a powerful nitroamine explosive was predicted. The heat of formation (HOF) of hetero pentacycloicosane nitro compound of dodecanitrododecazapentacyclo[9.5.1.1. 1. 1]icosane (DNDAPI or, alternatively, tetracycloHMX) was obtained by using density functional theory B3LYP method with 631G* basis set. The isodesmic reactions designed for the evaluation of HOF keep most of the basic ring structures of the title compounds and thus ensure the credibility of the result. The value of HOF is 1394.59 kJ/mol. The predicted detonation velocity of the title compound is 10.6 km/s and detonation pressure is 56.8 GPa, even at 90% of its theoretical density. These values are much larger than those of the widely used 1,3,5,7tetranitro1,3,5,7tetraazacyclooctane (HMX), indicating that DNDAPI is a promising candidate of high energy material. The dissociation energy for the NNO2 bond in the cage skeleton of the title compound is 125.36 kJ/mol. Journal of Energetic Materials 02/2009; 27(2):133143. DOI:10.1080/07370650802405299 · 1.36 Impact Factor

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ABSTRACT: Computations by density functional theory (DFT) method were performed on a series of pyrazole derivatives. The heats of formation (HOFs) were predicted using B3LYP and B3P86 functionals with augccpVDZ and 6311++G∗∗ basis sets via designed isodesmic reactions. In the isodesmic reactions the pyrazole was chosen as a reference compound. The general trend is that the HOFs increase with increasing number of –NH2 and –N3 groups. And the HOFs initially decrease then increase as the number –NO2 and –NF2 groups increasing. The HOF of 3,5didifluoroaminopyrazole is the smallest (134.4 kJ/mol), and the HOF of 3,4,5triazidopyrazole is the largest (1240.6 kJ/mol) at the B3LYP/augccpVDZ level. The position of the group also affects the HOFs. Judged by the HOF values, the 4 and 3monosubstituted isomers are the most stable monosubstituted isomers when the electron pulling and pushing groups are attached to the pyrazole ring, respectively. The 3,5isomers are the most stable disubstituted isomers. The values of HOFs decrease as the –NO2 groups being replaced by the –NH2 and –NF2, but increase dramatically as the –NO2 groups being replaced by –N3 with the average increment of 332.0 kJ/mol. The relative stability of the title compounds was evaluated based on the calculated HOFs and the energy gaps between the frontier orbits. Thermal stabilities were evaluated via bond dissociation energies (BDE) at the UB3LYP/augccpVDZ level. The value of C–N3 bond dissociation energy, 524.5 kJ/mol in average, is relatively larger than other outofring C–N bonds. The BDEZPE value of C–NO2 bond is smaller than all the other C–N bonds, which is 270.7 kJ/mol in average. These results provide basic information for the molecular design of novel high energetic density materials. Journal of Molecular Structure THEOCHEM 02/2009; 896(13):96102. DOI:10.1016/j.theochem.2008.11.004 · 1.37 Impact Factor

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ABSTRACT: The density functional theory (DFT) BLYP and B3LYP method with 321G* and 631G** basis sets were used to predict the structures, natural bond orbital (NBO) atomic charges, and ring interactions of 2,4,6tris(3',5'diamino2',4',6'trinitrophenylamino)1,3,5triazine (PL1). Approximately, the molecule possesses C3 symmetry with three benzene rings tilted to the triazine plane. The interactions among three 3',5'diamino2',4',6'trinitrophenylamino groups are of additivity. The heat of formation of PL1 was estimated to be 427.6 J/mol via isodesmic reaction. Detonation velocity and pressure are 8.5 km/s and 35.5 GPa, respectively. Journal of Energetic Materials 01/2009; 27(1). DOI:10.1080/07370650802182567 · 1.36 Impact Factor

Source Available from: Hui Liu
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ABSTRACT: The structural and thermodynamic properties of 75 polychlorinated thianthrenes (PCTAs) in the ideal gas state at 298.15 K and 1.013 ×105 Pa have been calculated at the B3LYP/6 31G* level using Gaussian 98 program. Based on the output data of Gaussian, the isodesmic reactions were designed to calculate standard enthalpy of formation (∆fH ө ) and standard free energy of formation (∆fG ө ) of PCTAs congeners. The relations of these thermodynamic parameters with the number and position of Cl atom substitution (NPCS) were discussed, and it was found that there exists high correlation between thermodynamic parameters (total energy (TE), zeropoint vibrational energy (ZPE), thermal correction to energy (Eth), heat capacity at constant volume (Cv ө ), entropy (Sө), enthalpy (Hө), free energy (Gө), standard enthalpies of formation (∆fH ө ) and standard Gibbs energies of formation (∆fG ө )) and NPCS. On the basis of the relative magnitude of their ∆fG ө , the order of relative stability of PCTA congeners was theoretically proposed. In addition, the correlations between structural parameters and NPCS were also discussed. The good correlations were found between molecular average polarizability (α), energy of the highest occupied molecular orbital (EHOMO), molecular volume (Vm) and NPCS, and all R 2 values are larger than 0.95. Moreover, Chinese Journal of Structural Chemistry 10/2008; 27:12551260. · 0.48 Impact Factor

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ABSTRACT: The molecular geometries of 209 polybrominated diphenyl ethers (PBDEs) were optimized at the B3LYP/631G level with Gaussian 98 program. The calculated structural parameters were taken as theoretical descriptors to establish two novel QSPR models for predicting supercooled liquid vapor pressures (P(L)) and octanol/air partition coefficients (K(OA)) of PBDEs based on the theoretical linear solvation energy relationship (TLSER) model, respectively. The two models achieved in this work both contain three variables: most negative atomic partial charge in molecule (q()), dipole moment of the molecules (mu) and mean molecular polarizability (alpha), of which R(2) values are both as high as 0.997, their rootmeansquare errors in modeling (RSMEE) are 0.069 and 0.062 respectively. In addition, the Fvalue of two models are both evidently larger than critical values F(0.05) and the variation inflation factors (VIF) of variables herein are all less than 5.0, suggesting obvious statistic significance of the P(L) and K(OA) predicting models. The results of LeaveOneOut (LOO) crossvalidation for training set and validation with external test set both show that the two models obtained exhibited optimum stability and good predictive power. We suggest that the QSPRs derived here can be used to predict accurately P(L) and K(OA) for nontested PBDE congeners from MonoBDEs to HeptaBDEs and from MonoBDEs to HexaBDEs, respectively. Science of The Total Environment 02/2008; 389(23):296305. DOI:10.1016/j.scitotenv.2007.08.023 · 4.10 Impact Factor

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ABSTRACT: Heats of formation (HOFs) and strengths of group interactions for 19 polyisocyanoadamantanes were obtained by using the density functional theory (DFT). The adamantane skeleton was chosen for a reference compound in the process of designing isodesmic reactions. It was found that the HOF increases 213–252kJ/mol for each additional number of the isocyano group being added to the adamantane skeleton. The HOFs slightly deviate from the group additivity with respect to the isocyano group. The distance between isocyano groups influences the values of HOFs. The disproportionation energies of neighbor isocyano groups in polyisocyanoadamantanes are in the range of 10.3–15.8kJ/mol, which are also slightly related to the substituent numbers. The average interaction energy between nearest neighbor –NC group in decaisocyanoadamantane is 10.34kJ/mol at the B3LYP/6311G∗∗ level. The relative stability related to the number of isocyano groups of the title compounds was evaluated based on the calculated HOFs, the energy gaps between the frontier orbitals, the bond orders of the C–NC and C–C bonds, and bond dissociation energies. Journal of Molecular Structure THEOCHEM 09/2007; 817(1):510. DOI:10.1016/j.theochem.2007.04.021 · 1.37 Impact Factor

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ABSTRACT: The number of Cl substitution positions (N(PCS)) of all 209 possible molecular structure patterns of polychlorinated diphenyl ethers (PCDEs) were correlated with their partition properties noctanol/water partition coefficient (lgK(ow)) and subcooled liquid water solubilities (lgS(w,l)). The correlation coefficients (R) and the leaveoneout (LOO) crossvalidation correlation coefficients (R(cv)) of all the 6descriptor models for lgK(ow) and lgS(w,l) are more than 0.98. By using stepwise multiple regression (SMR), the best two models of lgK(ow) with three descriptors (R=0.9,913) and lgS(w,l) with four descriptors(R=0.9,818) were obtained respectively. Based on these equations, the two properties of all 209 PCDEs were predicted. Model validation showed that the two models exhibit optimum stability and high predictive power. Moreover, results of prediction were further compared with data from similar studies by molecular connectivity indices (MCIs) and PM3 methods. Science of The Total Environment 09/2007; 382(1):5969. DOI:10.1016/j.scitotenv.2007.04.014 · 4.10 Impact Factor

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ABSTRACT: Optimized calculation of 135 Polychlorinated Dibenzothiophenes (PCDTs) was carried out at B3LYP/631G* level with Gaussian 98 program. The structural and thermodynamic parameters identified with the Theoretical Linear Solvation Energy Relationship (TLSER) model were employed as theoretical descriptors in the Quantitative Structure–Retention Relationship (QSRR) models derived to predict Retention Indices (RI) of PCDTs. Two QSRR models developed for RI of PCDTs contain only one variable: the mean molecular polarizability (α) and entropy (S⊖), respectively. The best fitted equation for the correlation between RI and α of 25 PCDTs with experimental data was RI=−126.52(±2.86)+0.97(±0.01)α with R2 as 0.9942, SD as 2.22, suggesting high accuracy of the RI predicting model. The correlation between RI and S⊖ is strong, and the equation was RI=−184.17 (±3.09)+0.48(±0.01)S⊖ with R2 as 0.9961, SD as 1.81. Furthermore, using position of Cl substitution (NPCS) method, QSRR model of PCDTs was obtained: RI=6.23(±0.75)+13.36(±0.19)N with R2 as 0.9953, SD as 1.99. Method validation also showed that the three models of this study exhibit optimum stability. Finally, RI values of 110 PCDT congeners without experimental value were also predicted with the three models, respectively. QSAR & Combinatorial Science 08/2007; 26(8):889  896. DOI:10.1002/qsar.200630150 · 1.55 Impact Factor

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ABSTRACT: Optimized calculation of 75 Polychlorinated Dibenzopdioxins (PCDDs) and their parent compound DD was carried out at B3LYP/631G* level with GAUSSIAN 98 program. The structural parameters identified with the Theoretical Linear Solvation Energy Relationship (TLSER) model were employed as theoretical descriptors in the Quantitative Structure–Property Relationship (QSPR) models derived to predict the aqueous solubility (−lgSw) and noctanol/water partition coefficients (lgKow) of PCDDs. The regression model obtained to predict −lgSw contains only one variable: the mean molecular polarizability (α). The best fitted equation for the correlation between −lgSw and α of 12 PCDDs was −lgSw=−3.6425+0.0693α with r2 as 0.9776, Standard Deviation (SD) as 0.30, and suggesting high accuracy of the −lgSw predicting model. At the same time, there exists high correlation (r2=0.8862) between noctanol/water partition coefficients (lgKow) and the mean molecular polarizability (α), and the SD is small. The mean molecular polarizability (α) is the only theoretical descriptor used in the QSPR model derived to predict lgKow. QSAR & Combinatorial Science 03/2007; 26(3):352  357. DOI:10.1002/qsar.200610008 · 1.55 Impact Factor

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ABSTRACT: The hybrid DFT methods with 12 different basis sets were used for the computation of FOOF. Comparison with CCSD/6311+G* method was made. The availability and shortcoming of DFT methods for FOOF were pointed out. On that basis, the binary compounds of fluorine and oxygen (OnFm, n=1–3, m=1–2) were calculated at the G96PW91/D95(3df) level. The affiliation of lone pair electrons toward the fluorine atom decreases from OF2 to O3F2 as the number of oxygen increases. The strength of O–O bond decreases from O2F2 to O3F2. The shorter O–F bond of O3F2 could readily change to longer one and vice versa through a transition state with energy barrier of 11.06kJ/mol. The O–F bond is much stronger than the O–O bond in O3F2. On the contrary, the O–F bond is much weaker than the O–O bond in O2F2. O2F and O3F can be regarded as weakly bound OO–F and OO–OF adducts, respectively. O3F2 could be regarded as a weakly bound FO–OOF adduct. The standard enthalpies and free energies of formation for the binary compounds were predicted at both the G96PW91 and the G2 levels. Journal of Molecular Structure THEOCHEM 03/2007; 804(1):95100. DOI:10.1016/j.theochem.2006.10.017 · 1.37 Impact Factor

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ABSTRACT: Optimized calculation of 209 PCBs was carried out at B3LYP/631G* level in Gaussian98 program to obtain their structural parameters. It was found there is significant correlation between the Cl substitution position and some structural parameters such as α (r2=0.9972), EHOMO (r2=0.8874) etc. Consequently the numbers of Cl substitution positions (N) were taken as theoretical descriptors to establish the novel QSPR model for predicting noctanol/water partition coefficients (logKow) of all PCB congeners, which can be used directly without computation of their complex structural and thermodynamic parameters. The new model achieved in this work contains three variables, of which r2=0.9497 and q2=0.9465. In addition, the variation inflation factors (VIF) of variables in the present model are all less than 5.0, suggesting high accuracy of the logKow predicting model. And the results of crossvalidation test and method validation (r2=0.9640 and q2=0.9606) also showed the models of this study exhibited optimum stability, convenience for use and better predictive power than that from AM1 method. QSAR & Combinatorial Science 04/2006; 25(4):333  341. DOI:10.1002/qsar.200530141 · 1.55 Impact Factor

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ABSTRACT: Three quantitative structureretention relationship (QSRR) models have been developed for gas chromatographic relative retention indices (RIs) of polychlorinated naphthalene (PCN) congeners. With computation at HF/631G* and B3LYP/631G* levels in Gaussian98 program, the structural parameters of PCNs were obtained and used as chemical descriptors to correlate with their gas chromatographic RIs by multiple linear regression analysis, resulting in model 1 and model 2. The squared correlation coefficients (r2) of the first two models are 0.9814 and 0.9957, and the crossvalidation correlation coefficients (q2) are 0.9771 and 0.9948, respectively. On the other hand, the third model, model 3, was developed using the relative position of chlorine substitution as molecular descriptor, and its multiple squared correlation coefficient is r2 = 0.9967 and q2 = 0.9959, suggesting model 3 is practical and especially has a optimum predictive power. QSAR & Combinatorial Science 01/2006; 25(1):7  14. DOI:10.1002/qsar.200530111 · 1.55 Impact Factor

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ABSTRACT: The optimized calculation of dibenzofuran (DF) and 135 polychlorinated dibenzofurans (PCDFs) was systematically carried out at the B3LYP/631G* level, and their total energy (E), enthalpy (H0), entropy (S0) and free energy (G0) were all obtained. Based on observation of the dependences of the thermodynamic parameters on the number and the position of chlorine substitutions, it was suggested that PCDFs with chlorines at 1 and 9 positions synchronously are less stable than at ortho positions. By designing isodemic reactions, standard heat of formation (ΔHf0) and free energy (ΔGf0) were calculated, from which the relative stability order of PCDFs was determined. Based on comparison of the stability order with the observed percentage of hexachlorinated dibenzofurans (HexaCDFs) and heptachlorinated dibenzofurans (HeptaCDFs) in the ash, fly ash and soil from incinerator, the stability order of the former is basically in consistency with that of the latter. The thermodynamic parameters of PCDFs achieved in the present study thus possess higher precision than those obtained by semiempirical methods in the past researches, and it is therefore of significance to the study of formation mechanism of dioxins. Journal of Molecular Structure THEOCHEM 07/2005; 725(1):5562. DOI:10.1016/j.theochem.2005.01.037 · 1.37 Impact Factor

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ABSTRACT: Based on MLSER model and quantum chemical descriptors computed at HF/STO3G, HF/LANL2DZ, B3LYP/LANL2D and B3LYP/631G* levels, different quantitative structureactivity relationships (QSARs) to the toxicity logEC50 and logLC50 of 28 alkyl(1phenylsulfonyl) cycloalkanecarboxylates were obtained. It is suggested that the eight models developed in the present study all have good correlation and relatively small error, in which the two models with three variables, polarizability, EHOMO and limit charge density from B3LYP/631G* level, exhibited the best optimal correlation (r2=0.9455, 0.9411; and q2=0.9289, 0.9162, respectively) and smallest error, and thus are advantageous to other models. It was also found that polarizability is the most significant factor influencing toxicity. The toxicity increased with increasing polarizability, while decreased with increasing dipole moment and decreasing of EHOMO. QSAR & Combinatorial Science 03/2005; 24(2):211  217. DOI:10.1002/qsar.200430873 · 1.55 Impact Factor

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ABSTRACT: The thermodynamic function, including total energy (TE), enthalpy (H0), entropy (S0) and free energy (G0) for 204 polychlorinated biphenyls (PCBs), were predicted by fully optimized calculation at the B3LYP/631G* level. With design of isodemic reactions, the standard formation heat (ΔHf0), standard formation free energy (ΔGf0) of PCBs were obtained. In addition, the dependences of these thermodynamic parameters on the number and position of chlorine substitute were discussed. It was suggested that TE, H0 and G0 of PCBs vary greatly with chlorine substitute at different positions, in which the order of increase of parameter value being position 2(6)≫position 3(5)>position 4. It was also found that the data of these thermodynamic parameters all increase in the case of the two chlorine substitutes at the same aromatic ring, compared with that at two aromatic rings, the increase effect being ortho≫meta>para. With addition of each chlorine atom in PCB, the increase of S0 is about 30J/molK, and also the relative stability of PCB congeners at 573.15K was proposed in this work. Journal of Molecular Structure THEOCHEM 02/2005; 714(2):123131. DOI:10.1016/j.theochem.2004.08.060 · 1.37 Impact Factor