The determination of the second-order rate constants for the ozonolysis of polychlorinated biphenyls in a participating solvent

摘要

The second-order rate constants for the ozonolysis of individual polychlorinated biphenyl congeners as well as a commercial mixture of congeners, Aroclor 1248, were determined in aqueous solution. Competitive and pseudo first-order kinetic methods were utilized in elucidating the rate constants. Rate constants for the polychlorinated biphenyls were determined competitively versus dibenzofuran for which the rate constant has been previously determined and is well known. A saturated solution of ozone was mixed with a saturated solution of PCBs and dibenzofuran. Aliquots were taken and the reaction was quenched with KI. The unreacted PCBs and dibenzofuran were extracted and the relative concentrations of the remaining PCBs and dibenzofuran were determined via gas chromatography - mass spectroscopy. Rate constants determined ranged from 25.5 $pm$ 5.6 $rm Msp{-1}ssp{-1}$ for biphenyl to 6.3 $pm$ 0.8 $rm Msp{-1}ssp{-1}$ for 2,4$spprime$,5-trichlorobiphenyl. The rate constants decreased by a factor of two upon the substitution of additional chlorines. The positions of the substituted chlorines were found not to affect the rate constants within a group of isomers.