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Geometrical configurations of 16 substituted biphenyls were computed at the B3LYP/6-311G** level with Gaussian 98 program. Based on linear solvation energy theory, lgKow as well as the structural and thermodynamic parameters obtained at this level was taken as theo- retical descriptors, and corresponding equation predicting the toxicity of Daphnia magna (–lgEC50) was thus obtained, in which three parameters were contained, i.e., n-octanol/water partition coefficients (lgKow), dipole moment of the molecules (μ) and entropy (S°). For this equation, R2 = 0.9582, q2 = 0.8921 and SD = 0.102. The absolute t-scores of three variables are larger than the standard one in the confidence range of 95%, which confirms the creditability and stability of this model.
Geometrical configurations of 16 substituted biphenyls were computed at the B3LYP / 6-311G ** level with Gaussian 98 program. Based on linear solvation energy theory, lgKow as well as the structural and thermodynamic parameters obtained at this level was taken as theo- retical descriptors , and corresponding equations predicting the toxicity of Daphnia magna (-lgEC50) was thus obtained, which among the three parameters were contained, ie, n-octanol / water partition coefficients (lgKow), dipole moment of the molecules °). For this equation, R2 = 0.9582, q2 = 0.8921 and SD = 0.102. The absolute t-scores of three variables are larger than the standard one in the confidence range of 95%, which confirms the creditability and stability of this model .