MICELLAR EFFECTS IN THE ACID DENITROSATION OF N-NITROSO-N-METHYL-PARA-TOLUENESULFONAMIDE

The acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) has been studied in the presence of anionic, cationic, and nonionic surfactants. Both cationic and nonionic micelles inhibit the reaction through an effective association of the substrate to the micellar pseudophase. This bound substrate becomes unreactive due to the absence of protons in the micellar Stern layer. The kinetic results allow a quantitative estimation of the association constants. The reaction has also been studied in the presence of anionic surfactants, both functionalized and nonfunctionalized. With hydrogen dodecyl sulfate, the reaction is accelerated by the presence of surfactant and reaches a limiting value at high concentrations. The reaction with sodium dodecyl sulfate shows a familiar pattern of behavior, with the reactivity passing through a maximum as the concentration of surfactant is increased. These facts can be quantitatively understood in terms of the pseudophase ion-exchange model, assuming a constancy in the degree of micellar fraction charge neutralized. Numerical values for the rate constants in the micellar pseudophase could be obtained and compared with those in water. Association constants between MNTS and micellar aggregates can also be obtained as well as the equilibrium exchange constants between Na+ and-protons. The study of the system in the presence of added NaCl, KCl, and CsCl provided further test for the kinetic model as well as the estimation of other ion-exchange constants. © 1990 American Chemical Society.