Octanol−Water Partition Coefficients of Non-Ortho- and Mono-Ortho-Substituted Polychlorinated Biphenyls

The octanol/water partition coefficients (K ow) at 25 °C were determined for 12 non-ortho- and mono-ortho-substituted polychlorinated biphenyls (PCBs). A generator-column/extractor-column technique was used, followed by off-line GC/ECD analysis. The relative standard deviations for the measurements ranged from 2.2 to 11.5%. The results were compared with both experimental and estimated literature values. Log K ow values determined for 12 congeners ranged from 6.47 to 7.15 and generally increased with an increase in molecular weight. Within homologue groups, congeners with less ortho-substitution generally have greater K ow values. The log K ow values of 46 congeners measured by the generator-column method from the literature and from this study were compiled and used for evaluation of quantitative structure−property relationships (QSPRs) relating the chlorine substitution pattern to the K ow. A useful equation to estimate log K ow was derived on the basis of multiregression analysis, which employs easily calculable molecular descriptors. The validity of this equation is demonstrated by comparing the estimated values with experimental values. This newly developed model agrees well with other model predictions. The empirical data-fitting approach based on coefficients related to chlorine substitution patterns appears promising.