Effect of [NaBr] on the rate of intramolecular base-assisted piperidinolysis of ionized phenyl salicylate in the presence of double-tail cationic surfactant aggregates: DDABr/NaBr/H2O nanoparticles catalysis

Abstract

The nucleophilic reactions of piperidine with ionized phenyl salicylate (PSa^‒) reveal a nonlinear decrease with the increase in concentration of didodecyldimethylammonium bromide (DDABr) micelles (D_n) at 35 °C and in the absence as well as presence of constant [NaBr]. The plots of pseudo-first-order rate constants (k_obs) versus [D_n]) have been explained quantitatively in terms of pseudophase micellar model. Such a data treatment gives DDABr micellar binding constant (K_S) of PSa⁻. The effects of [NaBr] upon K_S is explained with an empirical relationship which provides an empirical constant (K_Br/S where S = PSa⁻). The magnitude of K_Br/S is the measure of the ability of ion Br⁻ to expel the co-ion PSa⁻ from the cationic micellar pseudophase to the bulk aqueous phase. The origin of the large catalytic effect of DDABr/NaBr/H₂O nanoparticles on the rate of piperidinolysis of PSa⁻ is described in terms of plausible physicochemical causes.