Classification of calorimetric titration plots for alkyltrimethylammonium and alkylpyridinium cationic surfactants in aqueous solutions

Calorimetric titration plots for deaggregation of micelles formed by alkylpyridinium and alkyltrimethylammonium surfactants are classified into three types, A, B and C, depending on the shape of the plot of the enthalpy of dilution as a function of surfactant concentration. For Type A plots the recorded heat of injection q changes sharply between two parts of the titration curve over which the recorded heats are effectively independent of the composition of the solution in the sample cell. For Type B plots, the change is less sharp and both parts of the plot show dependences of heat q on solution composition, a pattern accounted for in terms of solute-solute interactions. Type C plots are complicated, in that no sharp change in q is recorded, the complexity of the plots being accounted for in terms of micelle-monomer equilibria over a range of surfactant concentrations and related enthalpies of deaggregation

Interaction and Activation in Aqueous Solutions

The extent to which the properties of neutral solutes in dilute aqueous solution deviate from ideal can be related to pairwise Gibbs energy interaction parameters. These pairwise interaction parameters can be re-expressed in terms of group-group interaction parameters. Extension of these concepts to solute-initial state and solute-transition state interactions is reviewed in the context of understanding the effect of added solutes on rate constants for ester hydrolysis in aqueous solutions. Examples of application of the method of data analysis is reviewed and their significance discussed.