Hydroxide ion specific adsorption on cetyltrimethylammonium bromide micelles explains kinetic data

Effect of Urea on the Kinetics of the Alkaline Hydrolysis of Crystal Violet Catalyzed by Aqueous Micellar Solutions of Cetyltrimethylammonium Bromide

“…For CTAB in aqueous solution at 25 ºC, the CMC was determined as 9.0×10 -4 M, which is in agreement with literature data [13,24,25] . The value of  was determined as 0.25 and total fraction of micellar head groups neutralized () was therefore 0.75, which also agrees with literature [23,26] .…”

“…The k ' vs. These results clearly indicate that it is the micelle which is responsible for enhancing the rate of the hydrolysis of crystal violet [23,[25][26] .…”

“…(1.94×10 -5 s -1 [30] ) for the reaction with water to the apparent pseudo-first-order rate constant is not negligible and therefore its contribution was taken into account by simply adding the term Fig. 3) was satisfactory and the optimized parameters are also comparable to literature [25,28,31] .…”

“…The PIE model assumes distribution of the substrate between the two phases to obey the simple distribution law with a constant substrate partition coefficient K s , and the distribution of the reactive nucleophile OH -ion to obey the simple ion-exchange equilibrium with the unreactive counter ion Br -of the surfactant according to [25,28,31] [ [3] with ion-exchange equilibrium constant OH Br K . Here M and W denote the micellar and aqueous phase, respectively.…”

“…With a proper choice of surfactant the rate of a reaction can be enhanced 5-1000-fold compared to the same reaction in the absence of a surfactant [23][24][25][26][27][28][29][30][31][32] . A substantial body of data has established beyond reasonable doubt that the partitioning of substrates into micelles in aqueous solutions produces observed catalysis when the surfactant concentration exceeds the CMC [31][32][33][34][35][36][37][38][39][40] .…”