MP6 Quantitative Structure Activity Relationships (QSARs)
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(AAA-1117-704646) QSARs for the acute toxicity of halogenated benzenes to bacteria in natural waters.

Lu, Guanghua¹, Wang, Chao¹, ¹ College of Environmental Science and Engineering, Hohai University, Nanjing, Jiangsu Province, P. R. China

ABSTRACT- The concentration values causing 50% inhibition of bacteria growth (24h-IC₅₀) were determined according to the bacterial growth inhibition test method. The energy of the lowest unoccupied molecular orbital and the net charge of carbon atom of 20 halogenated benzenes were calculated by the quantum chemical MOPAC program. The log1/IC₅₀ values ranged from 4.79 for 2,4-dinitrochlorobenzene to 3.65 for chlorobenzene. The quantitative structure-activity relationship model was derived from the toxicity and structural parameters data: log1/IC₅₀ =-0.531(E_LUMO)+1.693(Q_C)+0.163(logP) +3.375. This equation was found to fit well (r² =0.860, s=0.106), and the average percentage error was only 1.98%. Halogenated benzenes and alkyl halogenated benzenes are non-polar narcotics, and have shown hydrophobicity-dependent toxicity, the halogenated phenols and anilines exhibit toxic potency higher than that estimated by their hydrophobicity, whereas 2,4-dinitrochlorobenzene is electrophile with the halogen acting as the leaving group.

Key words: River bacteria, Acute toxicity, QSARs, Prediction model