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


Razak, Norazizah Abdul; Fagge, Ibrahim Isah; Khan, Mohammad Niyaz

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 (Dn) at 35 °C and in the absence as well as presence of constant [NaBr]. The plots of pseudo-first-order rate constants (kobs) versus [Dn]) have been explained quantitatively in terms of pseudophase micellar model. Such a data treatment gives DDABr micellar binding constant (KS) of PSa. The effects of [NaBr] upon KS is explained with an empirical relationship which provides an empirical constant (KBr/S where S = PSa). The magnitude of KBr/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.


Keyword(s)

Kinetics, Pseudophase micellar model, Counterion binding-micellar growth, Phenyl salicylate, Piperidine, Cationic micelles, Didodecyldimethylammonium bromide

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