REDOX AND REDUCTION POTENTIALS AS PARAMETERS TO PREDICT THE DEGRADATION PATHWAY OF CHLORINATED BENZENES IN ANAEROBIC ENVIRONMENTS

The anaerobic degradation pathway of hexachlorobenzene starts with a s eries of reductive dehalogenation steps. In the present paper it was e valuated whether the dehalogenation pathway observed in microbial ecos ystems could be predicted by the redox potential and/or the reduction potential (the latter determined in dimethylsulfoxide) of the various potential intermediates. It was found that these two parameters sugges t different pathways. The redox potential correctly predicts the domin ant pathway observed in microbial systems, while the reduction potenti al does not. The redox potential of the various redox couples showed n o correlation with the kinetic constants for the various dechlorinatio n steps as determined with a quantitative structure-activity relations hip developed for the environmental reductive dehalogenation of chlori nated aromatic compounds, even though both approaches predicted the sa me pathway.