ABSTRACT
Polyhalogenated aromatic compounds are environmental contaminants, with some of the most potent toxins being the polychlorinated dibenzo-p-dioxins. Knowledge of the mechanism of the photodehalogenation process could lead to efficient methods for decontamination and waste disposal. There have been several studies in the laboratory devoted to understanding the mechanism of photodehalogenation of polyhaloarenes. The presence of an electron donor has a dramatic effect on the regiochemistry of the photodehalogenation products. The chapter attempts to present the mechanism of photodechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD). The insolubility of 1,2,3,4-TCDD at higher concentrations in Acetonitrile is a limiting factor in providing evidence for triplet excimer formation. Polychlorobenzenes exhibit enhanced and efficient photodechlorination in the presence of electron donors. L. S. Hung and L. L. Ingram showed an enhanced degradation of octachlorodibenzo-p-dioxin in hexane with the addition of triethylamine. Photodechlorination was also shown to proceed substantially faster in the presence of Sodium borohydride.
