Premicelles of cetyltrimethylammonium methanesulfonate: Spectroscopic and kinetic evidence

The hydrolysis of methylnaphthalene-2-sulfonate (MeONs) is inhibited at high concentrations of cetyltrimethylammonium methanesulfonate (CTAOMs) above the critical micellar concentration, cmc, and accelerated at low concentration of it, below cmc. UV–vis spectra of MeONs were recorded in CTAOMs solutions, at different concentration, below and above cmc, and the substrate interacts differently with CTAOMs below and above the cmc. The hydrolysis of MeONs and its spectrum were investigated in two other systems for comparison purposes, using the same concentration range of CTAOMs: the zwitterionic tetradecyldimethylammonium propane sulfonate (SB3-14) surfactant, and the non-micellizing salt tetramethylammonium methanesulfonate (TMAOMs). The reaction is slightly monotonically inhibited in dilute SB3-14 and it is little affected by TMAOMs, whereas the spectrum of MeONs is not affected by the dilute solutions of both these two systems. The acceleration in dilute CTAOMs and the change of the MeONs spectra below and above cmc gives indication of premicelle formation in dilute CTAOMs.