The molecular geometries and electronic structures of 30 nitrobenzenes have been calculated by using semi-empirical MO AM1 and PM3 methods. EHOMO, ELUMO, ENHOMO, ENLUMO, AE, QNO2, Qc and V were selected as the structu...The molecular geometries and electronic structures of 30 nitrobenzenes have been calculated by using semi-empirical MO AM1 and PM3 methods. EHOMO, ELUMO, ENHOMO, ENLUMO, AE, QNO2, Qc and V were selected as the structural descriptors. The acute toxicity （-log/C50） of nitrobenzenes to tetrahymena pyriformis along with the above eight structural parameters was used to establish the quantitative structure-activity relationships （QSARs）. The results indicate that the established model based on AM I method is superior to that on PM3 method not only for the stability but also for the predictive powers of the model. Based on AM1 parameters, a further classifying discussion was presented for the study of nitrobenzene toxic mechanism. The results show that the substituents, nitro group and halogen substituents on the aromatic ring are crucial to the chemicals＇ toxicity. For nitrobenzenes without halogen or other substituent, the reduction of nitro group is the main route. However, for those with halogen substituents, their next lowest unoccupied molecular orbital may take part in the toxic action betweeen the chemicals and macromolecules, and ENLUMO has the most important effect on these chemicals＇ toxicity.展开更多
In this study,DFT-B3LYP level of theory with the 6-311G basis set was used to calculate a set of molecular descriptors of 36 nitrobenzenes.Quantitative structure-activity relationship（QSAR） models of the toxicity（p...In this study,DFT-B3LYP level of theory with the 6-311G basis set was used to calculate a set of molecular descriptors of 36 nitrobenzenes.Quantitative structure-activity relationship（QSAR） models of the toxicity（pIGC50） of 36 nitrobenzenes were established using some of the following calculated descriptors：HOMO energy（EHOMO）,LUMO energy（ELUMO）,the difference between LUMO and HOMO energy values（ΔE=ELUMO–EHOMO）,average polarizability（P）,dipole moment（μ）,molecular volume（V） and the charge of nitro group（Q-NO2）.The QSAR models obtained by employing stepwise multiple regression techniques are aimed at correlating the structures with their reported experimental toxicity values. Among the models presented in this study, statistically the most significant one is a two-parameter linear equation with the correlation coefficient （R2） of 0.896 and cross-validated correlation coefficient （R2cv） of 0.878. To further validate the predictive ability of the resulting model, external validation was carried out with R2~xt and Q^2,ext values of 0.894, 0.900, 0.909, 0.874, 0.885 and 0.903, respectively. This study also reconstructed the obtained models using AMl-based calculated descriptors to demonstrate the superiority of DFT over AM1 for quantum calculations of mechanical descriptors. The results were discussed in the light of the main factors that influence the toxicity of nitrobenznenes.展开更多
This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C cata...This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C catalyst, minor amount of water reduces the induction time, increases the reaction rate and reaction TOFs. Water might enhance the diffusion, adsorption and dissociation of H2 on Pd catalysts.展开更多
基金This work was supported by the National Natural Science Foundation of China (No.10576030)
文摘The molecular geometries and electronic structures of 30 nitrobenzenes have been calculated by using semi-empirical MO AM1 and PM3 methods. EHOMO, ELUMO, ENHOMO, ENLUMO, AE, QNO2, Qc and V were selected as the structural descriptors. The acute toxicity （-log/C50） of nitrobenzenes to tetrahymena pyriformis along with the above eight structural parameters was used to establish the quantitative structure-activity relationships （QSARs）. The results indicate that the established model based on AM I method is superior to that on PM3 method not only for the stability but also for the predictive powers of the model. Based on AM1 parameters, a further classifying discussion was presented for the study of nitrobenzene toxic mechanism. The results show that the substituents, nitro group and halogen substituents on the aromatic ring are crucial to the chemicals＇ toxicity. For nitrobenzenes without halogen or other substituent, the reduction of nitro group is the main route. However, for those with halogen substituents, their next lowest unoccupied molecular orbital may take part in the toxic action betweeen the chemicals and macromolecules, and ENLUMO has the most important effect on these chemicals＇ toxicity.
基金supported by the Natural Science Foundation of Yancheng Teachers University (08YCKL077)the Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources & Environmental Protection (JLCBE 07025)the Educational Bureau of Jiangsu Province (08KJD150021)
文摘In this study,DFT-B3LYP level of theory with the 6-311G basis set was used to calculate a set of molecular descriptors of 36 nitrobenzenes.Quantitative structure-activity relationship（QSAR） models of the toxicity（pIGC50） of 36 nitrobenzenes were established using some of the following calculated descriptors：HOMO energy（EHOMO）,LUMO energy（ELUMO）,the difference between LUMO and HOMO energy values（ΔE=ELUMO–EHOMO）,average polarizability（P）,dipole moment（μ）,molecular volume（V） and the charge of nitro group（Q-NO2）.The QSAR models obtained by employing stepwise multiple regression techniques are aimed at correlating the structures with their reported experimental toxicity values. Among the models presented in this study, statistically the most significant one is a two-parameter linear equation with the correlation coefficient （R2） of 0.896 and cross-validated correlation coefficient （R2cv） of 0.878. To further validate the predictive ability of the resulting model, external validation was carried out with R2~xt and Q^2,ext values of 0.894, 0.900, 0.909, 0.874, 0.885 and 0.903, respectively. This study also reconstructed the obtained models using AMl-based calculated descriptors to demonstrate the superiority of DFT over AM1 for quantum calculations of mechanical descriptors. The results were discussed in the light of the main factors that influence the toxicity of nitrobenznenes.
基金supported by the National Natural Science Foundation of China(Nos.20976164,21176221 and 21136001)National Basic Research Program of China(973 Program)(Nos. 2011CB710803,2013CB733500)Zhejiang Provincial Natural Science Foundation of China(No.LY12B03005)
文摘This study shows that minor amount of water plays a very important role in solvent-free hydrogenation of halogenated nitrobenzenes. For dried sponge Pd, the reaction cannot occur in the absence of water. For Pd/C catalyst, minor amount of water reduces the induction time, increases the reaction rate and reaction TOFs. Water might enhance the diffusion, adsorption and dissociation of H2 on Pd catalysts.
