Thermodynamics of fish-water and octan-l-ol water partitioning of some chlorinated benzenes

Preliminary results were reported for the elucidation of the thermodynamic properties of the exchange of hydrophobic chemicals (several polychlorobenzenes) between water and fish and the thermodynamics of the relationship between bioconcentration factors and octanol-water partition coefficients. Bioconcentration of polychlorobenzenes by fish was accompanied by positive enthalpy and entropy changes. The free energy of this process was dominated by the favourable entropy contribution. In the octan-l-ol water system partitioning of these compounds was accompanied by negative enthalpy and by small negative or positive entropy changes. The results suggested that octan-l-ol was a poor model of the fish lipids for predicting bioconcentration factors. Additionally, a first attempt was made to find extrathermodynamic relationships between molecular structure and enthalpy, entropy and free energy changes of the fish-water and octanol-water partitioning of chlorobenzenes.