Determination of solution aggregation using solubility, conductivity, calorimetry, and pH measurements

Compounds which aggregate or form micelles have an unusually high solubility and/or have a solubility which is very sensitive to temperature. Theoretical equations are derived which relate the data collected from conductivity and calorimetric experiments to the average aggregation number, equilibrium constant? and the enthalpy change for the aggregation. For the compound studied, the amount of aggregation occurring was found to be small with an aggregation number of 10-11 and an equilibrium constant of 10(10)-10(12). The cmc is temperature dependent, having a value of 0.033 M at 15 degrees C increasing to 0.045 M at 35 degrees C. The aggregation is primarily enthalpy driven and entropy disfavored. The aggregated compound has a lower pK(a) than the monomer, according to the pH data, indicating that the imidazole ring is less basic in the aggregate.