A Systematic Study on the Complexation of Quaternary Ammonium Salts and Neutral Phenols

概要

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Complexation of quaternary ammonium salts (Q^+X^-) and undissociated, neutral phenols (ArOH) in homogeneous organic solutions was systematically investigated to afford a reliable quantitative basis for a new model of anionic potentiometric response to neutral phenols, displayed by organic liquid membranes based on Q^+X^-. IR, ^1H- and ^<13>C-NMR, and UV studies indicated complexation of Q^+X^- and ArOH in 1 : 1 stoichiometry in nonpolar organic solvents such as benzene and chloroform. The stability constant (K_s) of the complex was affected by the acidity and lipophilicity of the ArOH component as well as the size of X^- of the Q^+X^- component; stronger complexes were formed by ArOH with a lower pK_a and higher log P_<oct>, as well as by Q^+X^- with a smaller ionic radius for X^-. These results suggest that the major driving force for complexation is hydrogen bonding interactions between X^- and the phenolic OH. The K_s values were found to be parallel with the magnitudes of anionic potentiometric responses by membranes based on Q^+X^-, indicating that the complexation of ArOH by Q^+X^- plays an important role in the anionic potentiometric responses. The significance of proton dissociation from the Q^+X^-・ArOH complex was also discussed.
公益社団法人日本薬学会の論文
1998-08-15