Estimation Of Octanol-Water Partition Coefficient Of Organic Compounds By Two-level Group-contribution Method

The octanol-water partition coefficient(K_ow) is one of the key parameters inquantitative structure-activity relationship (QSAR) studies of organic compounds, which isextensively used to describe a chemical's lipophilic or hydrophobic properties and its'environmental end-result. K_ow is also the important physical and chemical parameter forreflecting the trasformation of the organic compounds in environment. With the increasingquantity of artifical chemical, there are numerous organic compounds released in theenvironment. It is impossible and lagging that the K_ow depends on the experiment.Therefore, the predicted model is important for getting the K_ow.For amending the fault of current group-contribution methods, new methods namedtwo-level group contribution method for the estimation of the octanol-water partitioncoefficient of organic compounds are proposed. In this medol, The normal boiling pointand mole weight are necessary for predicting K_ow .According to the rule that the staticelectricity of the atom in different molecule is invariable, the organic compounds includinghydrocarbon, chloride compounds, oxygenous compounds and nitrogenous compounds aredivided into 69 first-level groups and 41 second-level groups. The experimental values of430 compounds are simulated, which including alkane, alkene, alkyne, cycloalkane,aromatic compounds, condensed ring compounds, chloride alkane, chloride alkene,chloride aromatic, alcohol, phenol, ketone, ether, ester, amine, nitrogenous heterocycliccompounds and nitryl compounds. As a result, the values of 69 first-level groups and 41second-level groups to octanol/water partition coefficient and the parameters in theequation are obtained. The average correlation accuracy of above compounds is 7.25% bythe simple-level group-contribution method. As for alkane, alkene, chlorinated compoundsand oxygenous compounds ,the correlation accuracy is decreased by 1.86% by drawinginto second-level groups.Compared with three-level group-contribution approach ,atom/fragment contribution method(AFC) and molecular connectivity index method bycalculating logK_ow of 31compounds beyond regression ,the accuracy of the medol proposedis priority to other three methods .