Kinetics and mechanism of nanoparticles (CTABr/MX/H2O)-catalyzed piperidinolysis of ionized phenyl salicylate. 1

• MX/CTABr nanoparticles-catalyze rate of reaction of Pip with PSa−.
• Catalytic effect of 3,5-Cl2BzNa(MX) is 9-fold larger than that of 2,3-Cl2BzNa(MX).
• Empirical linear relationship between kcat and RXBr for different X.
• Values of RXBr are 25 and 206 for X = 2,3- and 3,5-Cl2C6H3CO2−, respectively.
• Plausible explanation of RXBr values for X = 2,3- and 3,5-Cl2C6H3CO2−.

Apparent catalytic effects of varying concentration of CTABr/MX/H2O nanoparticles (at a constant [CTABr] and [Piperidine]) on pseudo-first-order rate constants (kobs) for the reaction of piperidine with ionized phenyl salicylate have been measured as kobs/k0 where kobs and k0 represent rate constants in the presence and absence of MX, respectively. Symbols CTABr and MX represent respectively cetyltrimethylammonium bromide and 2,3- or 3,5-Cl2BzNa with Bz− = C6H3CO2−. At 6 mM CTABr, the maximum values of kobs/k0 are 7.9 and 9.0 at 300 mM 2,3-Cl2BzNa and 80 mM 3,5-Cl2BzNa respectively. Several-fold larger catalytic effects of 3,5-Cl2Bz− than that of 2,3-Cl2Bz− are attributed to ∼8-fold larger CTABr binding constant of 3,5-Cl2Bz− than that of 2,3-Cl2Bz−. Origin of CTABr/MX/H2O nanoparticles catalytic effects is related to the ability and efficiency of the expulsion of another counterion S− by the counterion X− from the cationic nanoparticles to the aqueous phase by means of the ion exchange process X−/S− at the cationic surface of nanoparticles.