QSARs For The Toxicity Of Halogenated Benzenes To River Bacteria

With the development of the industry and agriculture and wide application of the chemicals, a large number of poisonous substances have come into the natural water body through various kinds of ways, and caused the water pollution. In order to protect the water resource, and rationally set density of permission and discharge standard of pollutant in water environment, many methods have been used to monitor and appraise the water body.The river water gathered from the Nanjing section of the Yangtze River as microorganism's source. 24h acute toxicity and 7d chronic toxicict of the halogenated benzenes to the river bacteria was determined separately by using the bacteria growth inhibition test, 24h-/C₅0 value and 7d-MATC values were obtained correspondingly. The results showed that the toxicity of the halogenated benzene compounds to the river bacterium was correlated with the kinds, quantity and position of substituents in benzene ring.The octanol/water partition coefficients (IgP) of 18 compounds was obtained from the software Biobyte.The various steps valence molecular connectivity index of compounds were calculated by using molecular connectivity index method, and the electrical parameter and spacial parameter of compounds was determined by MOPAC6.0-AM1.The quantitative structure-activity relationship (QSAR) models were developed for the acute and chronic toxicity by using the molecular connectivity index method, the quantum chemistry method and the group contribution method, and a series of QSAR models were obtained by using SPSS 10.0 software. All models of the squares of adjusted correlation coefficients were larger than 0.870, which showed the QSAR analyses are successful and the stability and predicting function are very good as well; The good relationships of toxicity of polar compounds and non-polar compounds was separately developed using octanol/water partition coefficient method.The toxicity of the halogenated benzene compounds to the river bacteria was mainly related to the molecular volume and Van Der Vaals area. With the increase of molecular volume and surface area, toxicity is stronger. In addition, the electronic factor of substituent influenced the toxicity of the chemical compound. The obvious positive correlation was found between the toxicity of both polar compounds and non-polar compounds and \gP. Polar narcotic chemicals, typified by most phenols and anilines, exhibit toxic potency higher than that estimated by their hydrophobicity due to the existence of polar substituents in the molecules. The toxicity of polar chemicals related to not only the partition between water and organism, but also the electrical factors.