Kinetic Effects of Added Electrolytes on a Micelle-Modified Reaction

The dehydrochlorination of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane, DDD, with hydroxide ion has been studied in several tretradecyltrimethylammonium bromide, TTAB, concentrations by varying [NaOH] from 0.01 mol dm -3 to 1.5 mol dm -3 . The dependence of the first-order rate constant on the hydroxide ion concentration cannot be explained on the basis of the pseudophase model. The kinetic effects of added electrolytes have been studied in TTAB micellar solutions. At low hydroxide ion concentrations the pseudophase model can rationalize the added salt effects. The influence of the electrolyte nature on the kinetic effects observed can be related to the competition between the anion of the salt and the hydroxide ions for the available sites at the surface of the TTAB micelles. At high hydroxide concentrations, a larger decrease in the reaction rate is found than that expected on the basis of the pseudophase model when the added salt concentration increases. The influence of the nature of the added electrolytes, at a given added salt concentration, is the same in the presence of [NaOH] = 0.02 mol dm -3 as in the presence of[NaOH] = 1 mol dm -3 for the 1:1 salts.