Influence of surfactants and surfactant-coated IONs on the rate of alkaline hydrolysis of procaine in the presence of PEG

Abstract

The influence of surfactant coated iron oxide nanocomposites (Surf-IONs) and surfactants on the rate of alkaline hydrolysis of procaine hydrochloride (2-diethylaminoethyl-4-aminobenzoic acid) in the presence of poly(ethylene glycol) (PEG) have been investigated under the varying reaction conditions. The nanoparticles were synthesised using the co-precipitation method and were characterised using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and Thermogravimetric analysis (TGA). The concentration of NaOH was taken in overabundance over [procaine] for maintaining the reactions under pseudo-first-order conditions. The kinetic effect of poly(ethylene glycol); PEG of molecular weights 1500, 4000, 6000, and 8000 with the cetyltrimethylammonium bromide; CTABr and sodium dodecyl sulphate; SDS (either free or coated on iron oxide nanoparticles) were studied. A fall in the values of the rate constant on increasing the [surfactant] or [Surf-IONs] at fixed [PEG] was observed. The kψ-[PEG-surfactant] profile was treated using the pseudophase model, and pseudophase ion exchange model and the kinetic parameters were determined. The binding constant of procaine with PEG-surfactant aggregates was found to be lower than the respective micelles in the absence of PEG. The increase in the molecular weights of PEG decreased the values of binding constants and equilibrium constants.