The hydrolysis of 2,4-dinitrochlorobenzene (DNCB) by mixed cationic micelles has been studied. The linear relation of k1 with mole fractions of surfactants in the mixed cationic micelles was obtained, where k1 is the first-order rate constant for the hydrolysis reaction of DNCB catalyzed by the mixed micellar solutions of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB). Because the cmc value of octyltrimethylammonium bromide (OTAB) was too large and the mole fraction of OTAB in CTAB/OTAB and CPB/OTAB mixed micelles was too small, the catalytic activity for hydrolysis of DNCB in these mixed micelles depended mainly on the concentration of CTAB or CPB. However, a negative deviation from the straight line in the plot of k1 vs. the mole fraction was observed. The added OTAB acted as a neutral inorganic bromide (like NaBr) in the CTAB/OTAB or CPB/OTAB mixed systems. The k1 increased with increasing the concentration of OTAB and NaBr. The above-mentioned results can be explained quantitatively with the pseudophase ion exchange (PIE) model.

Key words: SURFACTANTS, NITROBENZENE P, CHLOROBENZENE P, HYDROLYSIS, CATALYTIC ACTIVITY, PYRIDINE P