Characterization of the Photolysis of 2,4,5,2′,4′,5′-Hexabromobiphenyl

Characterization of the Photolysis of 2,4,5,2′,4′,5′-Hexabromobiphenyl. MILLIS, C. D., AND AUST, S. D. (1985). Fundam. Appl. Toxicol. 5, 546–554. 2,4,5,2′,4′,5′-Hexabromobiphenyl (2,4,5-HBB) was irradiated with ultraviolet light in hexane with stirring, and photolysis was monitored by gas chromatography (GC). 2,4,5-HBB decomposed at an average rate of 0.66±0.02 μmol/min and the reaction appeared zero order from 0.159 to 1.59 mM 2,4,5-HBB. Several polybrominated biphenyl (PBB) congeners were identified as photoproducts of 2,4,5-HBB. 2,4,5,2′,5′-Pentabromobiphenyl (-PBB), formed by para debromination, accumulated at a higher rate than did 2,4,5,3′,4′-PBB, formed by ortho debromination. 2,4,5,2′,4′-PBB was formed by meta debromination. 3,4,3′,4′-Tetrabromobiphenyl (-TBB) was found as a secondary photoproduct, formed by ortho debromination of 2,4,5,3′,4′-PBB. 2,5,2′,5′-TBB and 2,4,2′,5′-TBB were formed by debromination of 2,4,5,2′,5′-PBB para and meta, respectively. 2,5,3′,4′-TBB could be formed by either ortho debromination of 2,4,5,2′,5′-PBB or para debromination of 2,4,5,3′,4′-PBB. Rates of degradation and accumulation of the penta- and tetrabrominated biphenyls were also studied. The ultraviolet spectra of the 2,4,5-HBB photolysis mixture, as well as the purified components, were studied and are also reported