3,4,4 ,5-Tetrachlorobiphenyl PCB

Reported vapor pressures and Henry s law constants of 2,2, 5,5,-tetrachlorobiphenyl (PCB-52) at various temperatures and temperature dependence equations... 

In the rabbit, the nonplanar PCB 2,2, 5,5 -tetrachlorobiphenyl (2,2, 5,5 -TCB) is converted into the 3, 4 -epoxide by monooxygenase attack on the meta-para position, and rearrangement yields two monohydroxymetabolites with substitution in the meta and para positions (Sundstrom et al. 1976). The epoxide is also transformed into a dihydrodiol by epoxide hydrolase attack (see Chapter 2, Section 2.3.2.4). This latter conversion is inhibited by 3,3,3-trichloropropene-l,2-oxide (TCPO), thus providing strong confirmatory evidence for the formation of an unstable epoxide in the primary oxidative attack (Forgue et al. 1980). 

The PCBs are complex mixtures of substances which have been on the market since 1950. They are widely used, e. g., as transformer oil, hydraulic fluid, heat exchange medium, dielectric fluid in condensers, plasticizer and additive for printing ink. Formula 9.3 shows 2,2, 5,5 -tetrachlorobiphenyl (I) and 2,2, 4,5,5 -pentachlorobiphenyl (II) as examples. 

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