Collect. Czech. Chem. Commun. 1990, 55, 1435-1456

Studies of association in solution from permitivity measurements: Statistical problems

Otto Exner

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


Association of a solute can be followed by permittivity measurement which allows us in principle to calculate the equilibrium constant K and dipole moments of the monomer μM and dimer μD. However, the procedures used in the literature are unsatisfactory from the statistical point of view and the published values are mostly completely wrong. In all known examples their errors were badly underestimated. Using a correct statistical approach several examples have been now reevaluated. It is practically impossible to calculate reliably all three parameters from permittivity data of common accuracy. Better results are obtained if either μM or K can be determined in an independent way. A symmetrical structure of the dimer is preferable in several cases (acetic acid, 2-pyrrolidinenone) contrary to the previous claims.