Interaction between Alkyl Sulfates and Alkylbenzyldimethylammonium Chlorides

The effects of temperature, length of alkyl chain, and counter ion on the interaction between alkyl sulfates and alkylbenzyldimethylammonium chlorides in aqueous solutions have been studied by means of the conductometric method. The equilibrium constants (K) and the standard affinities (-Δμ°) of the reactions between them have been found to decrease with an increase in the temperature, but they increased with an increase in the length of the alkyl chain. The standard heats of reaction (-ΔH°) and the standard entropies (-ΔS°) increased with an increase in the length of the alkyl chain. The equilibrium constants and the thermodynamic parameters of the reactions were appreciably affected by the counter ions of the alkyl sulfates. It is suggested that the reactions between them are dependent on not only the electrostatic interaction between the oppositely-charged organic ions, but also on the interaction between the hydrophobic groups of the surfactants.