Computational Chemistry Study on Photolysis Pathway of Polychlorinated Biphenyls Dissolved in Surfactant Solutions

The direct photolysis of polychlorinated biphenyls (PCBs) was investigated in an anionic surfactant solution under ultraviolet irradiation. Based on the photoreaction experiments, the photodechlorination mechanism via excited singlet state was theoretically studied by molecular orbital (MO) calculations. The molecular geometry of the tested PCB congener optimized by the PM6 MO calculations, then the photolysis index ΔMij for the individual bond was calculated to examine the photo-induced bond cleavage on the basis of CNDO/S MO calculations. The calculation results demonstrated that photodechlorination of the tested PCB congener with preferential removal of ortho chlorine should be the predominant pathway. This conclusion agreed well with the previous researches and our photolysis experiments.