摘要
The relationship between chemical structures and photodegradation activity of 12 PAHs is studied using DFT and HF methods, and stepwise multiple linear regression analysis method. The equilibrium geometries and vibration frequency have been investigated by considering Solvent effects using a selfconsistent reaction field based on the polarizable continuum model. With DFT and HF methods, different quantum chemical structural descriptors are obtained by quantum chemical calculation and the results with DFT method are better for QSAR model. It is concluded that the photodegradation activity is closely related to its molecular structure. In the regression analysis, the main factors affecting photodegradation rate include the energy of the highest occupied orbital EHOMO and the number of six-carbon benzene ring N1, and the QSAR model successfully established is logkb = 6.046 + 54.830EHOMO + 0.272N1. Statistical evaluation of the developed QSAR shows that the relationships are statistically significant and the model has good predictive ability. EHOMO is the most important factor influcing the photodegradation of PAHs, because the higher EHOMO is, the more easily electron will be excited and the more easily molecular will be degraded. Comparison of the photodegradation of PAHs with their biodegradation shows that the committed step of biodegradation is that the effects of microorganisms make the chemical bond break, while in the committed step of photodegradation PAHs eject electrons.
The relationship between chemical structures and photodegradation activity of 12 PAHs is studied using DFT and HFmethods, and stepwise multiple linear regression analysis method. The equilibrium geometries and vibration frequency have beeninvestigated by considering Solvent effects using a selfconsistent reaction field based on the polarizable continuum model. With DFTand HF methods, different quantum chemical structural descriptors are obtained by quantum chemical calculation and the results withDFT method are better for QSAR model. It is concluded that the photodegradation activity is closely related to its molecular structureIn the regression analysis, the main factors affecting photodegradation rate include the energy of the highest occupied orbital EHOMOand the number of six-carbon benzene ring N1, and the QSAR model successfully established is logkb = 6.046 ＋ 54.830EnoMo ＋0.272N1. Statistical evaluation of the developed QSAR shows that the relationships are statistically significant and the model hasgood predictive ability. EHOMO is the most important factor influcing the photodegradation of PAHs, because the higher EHOMO is, themore easily electron will be excited and the more easily molecular will be degraded. Comparison of the photodegradation of PAHswith their biodegradation shows that the committed step of biodegradation is that the effects of microorganisms make the chemicalbond break, while in the committed step ofphotodegradation PAHs eject electrons.
基金
supported by the National Natural Science Foundation of China(Nos.40976041 and 20775074)
