ION-PAIR ASSOCIATION OF SUBSTITUTED PHENOLATES WITH K+ IN OCTANOL

The speciation, environmental distribution, and ultimate fate of pheno lic compounds, a class of hydrophobic ionizable organic compounds, is influenced by both their hydrophobic and electrostatic characteristics . In this study, electrical conductance measurements were employed to characterize the ion-pair association properties of a monovalent inorg anic cation (Ki) with substituted phenolate anions in the model hydrop hobic solvent, I-octanol. Quantification of such processes is importan t for characterizing the overall partitioning to and speciation in oct anol of phenolic compounds. Data were analyzed and association constan ts were calculated using a modified form of the Fuoss-Onsager equation for electrical conductivity. Results indicate that the magnitude of i on-pair association correlates with the electron-donating and -withdra wing characteristics of phenolic ring substituents. A quantitative str ucture-activity relationship was developed correlating ion-pair associ ation constants to the sum of Hammett substituent constants for each s pecies. The data suggest that for some phenolate salts, charged triple ion or higher aggregate formation may occur at elevated concentration s. A qualitative interpretation of this phenomenon and the selectivity of its occurrence are discussed.