Nine phthalates were calculated at the B3LYP/6-311G＊＊ level using DFT method. The corresponding linear relationship equations （R2 were 0.853 and 0.936 respectively） for the biodegradation rate （Kb） and half-life time （h/2） of biodegradation were obtained with the structural parameters as theoretical descriptors. Furthermore, CoMFA method was also applied to establish 3D models which revealed the fields influencing these properties. The relationship between the properties and the structure was obtained. The correlation coefficients of the models were 0.992 and 0.999, respectively. Analyses of 2D and 3D models demonstrated that the molecular volume was an important factor affecting the biodegradability of these compounds.
Using DFT method, 10 sulfonylurea herbicides were computed at the B3LYP/6- 31G＊ level. Based on linear solvation energy theory, the corresponding linear solvation energy relationship （LSER） equation （R2 -- 0.759） to the half-life time （T1/2） of biodegradation was obtained with the structural and thermodynamic parameters as theoretical descriptors. Furthermore, CoMSIA method was also applied to establish 3D models which reveal the fields influencing these properties. The relationship between the properties and the structure was obtained. And the related coefficient of the model is 0.952. Results showed the electronic property is important to affect the biodegradation of these compounds by analysis of the 2D and 3D models.
Structural and thermodynamic parameters of 16 chloro-phenol compounds in water solution were calculated and fully optimized by using Onsager model in self-consistent reaction field（SCRF） based on the B3LYP/6-311G＊＊ level.These quantum chemical parameters were used as theoretical descriptors to correlate with the experimental biodegradation rate constant（Kb） of 16 compounds by stepwise multiple linear regression.As a result,a three-parameter model including molecular average polarizability（α）,entropy（Sθ）,and molar heat capacity at constant volume（CVθ） were established for Kb prediction,which was proposed with correlation coefficient R2 = 0.894.α exhibits the most significant effect on Kb.Variance analysis and standard t-value test were applied to validate the model.As expected,this model exhibits good robustness and prediction ability,which can be used in Kb prediction of analogs.
