THE EFFECT OF MIXED MICELLES OF SURFACTANTS ON THE ALKALINE-HYDROLYSIS OF ESTERS

The alkaline hydrolysis of aromatic and normal aliphatic acid esters h ave been studied at 25 degrees C in mixed micellar solutions of surfac tants (Brij 35-SDS, Brij 35-DTAB, Brij 35 -TTAB, Brij 35 - CTAB, Trito n X - 100 - CTAB, Triton X - 100 - SDS) with UV spectrophotometry and the method of thermokinetics. The critical micellar concentrations of the corresponding systems have also been measured with UV spectrophoto metry in this paper. k(1m)in micellar pseudo-phase has been calculated . The ratios of k(1m)to k(1w)for all mixed micellar systems investigat ed are less than 1. The results indicate that these reactions are inhi bited by the mixed micelles, and the mixed micelles exhibit a greater effect of inhibition on the reactions than those do in corresponding s ingle oner. The reason for this is that the micropolarity of the compa ct Stern layer of mixed micelle is lower, and the microviscidity is hi gher. The inhibition effects also depend on tile hydrophobic chain len gth of the surfactants and the hydrophobicity of the substrate.