Relationship between the Biodegradability and Structure of Polycyclic Aromatic Hydrocarbons

21 Physicochemical and quantum chemical parameters of 17 kinds of polycyclic aromatic hydrocarbons were calculated by using semi-empirical MOPAC AM1 method. By means of Partial Least Squares (PLS), quantitative structure-biodegradation relationship (QSBR) study was performed with the logarithm of specific biodegradation rates (logKb). The optimal model was obtained, and the result showed that the first-order molecular connectivity index (1X), the energy of the lowest unoccupied molecular orbital (E1umo), logarithm of n-octyl alcohol/water partition coefficient (logP) and torsion energy (Et) are the dominant factors governing the biodegradability of polycyclic aromatic hydrocarbons, and the effect of second-order valence molecular connectivity index (2xv), the third-order valence molecular connectivity index (3Xv) and molar refractivity (Rm)should not be ignored.