A Vector Normalized Method-Assisted 3D-QSA2R Model and Its Application in the Molecular Modification of PCBs with Higher Flame Retardancy and Lower Toxicity

Abstract

Flame retardants are widely used in many materials and products, and there is a pressing need to enhance the performance of flame retardants while lowering their toxicity. In this paper, using polychlorinated biphenyl flame retardants as an example, a three-dimensional quantitative structure-double-activity relationship (3D-QSA2R) model, with the double activities of flame retardancy and toxicity, was constructed by introducing a vector normalized method to achieve the goal of environmental risk management and control the sources of chemicals. The results showed that the 3D-QSA2R model has good robustness and strong predictive ability. PCB-209 was used as a target molecule for the contour map analysis and molecular modification. The comprehensive values (C) of six novel PCB-209 molecules were increased by up to 53.61%. The physical and chemical parameters (frequency and Gibbs free energy), functional properties (stability and insulation) and the other three POP properties of the novel PCB-209 molecules showed that the Cl atom substitution reaction of PCB209 molecules could occur and exist stably in the environment. With improvement in stability, the insulation of six novel PCB-209 molecules was not influenced after modification, and the environmental persistence, bioconcentration and long-distance migration of six novel PCB-209 molecules were increased up to 99.47%, 15.29% and 100.9%, respectively. The flame retardancy and toxicity of the new molecules were verified by Gaussian software and the EPI database, respectively. The single activity verification values of flame retardancy and toxicity followed the trend of C values predicted by the double-activity 3D-QSA2R model established in this paper. The ratio between the two single activities of the new PCB-209 molecule generally conformed to the weight setting, which satisfies the purpose of setting the weight as the main way to improve the efficacy of flame retardants.