PH-DEPENDENCE OF THE BELOUSOV-ZHABOTINSKY REACTION IN WATER-IN-OIL REVERSE MICROEMULSION OF AOT IN OCTANE

The ferroin-catalyzed Belousov-Zhabotinsky reaction in water-in-oil mi croemulsion with anionic surfactant Aerosol OT exhibits chemical oscil lations in spite of its extremely high pH in the aqueous pseudophase. In order to elucidate the reaction mechanism, we have measured the rat e of autocatalytic step in the inorganic subset of the reaction under the batch conditions. We have found that the rate depends linearly on the concentration of H2SO4 and quadratically on the concentration of N aBrO3, in contrast to the dependence in the homogeneous aqueous soluti on in which both dependences are linear. The rate constant was found t o be an order of magnitude higher in the microemulsion than that in th e homogeneous aqueous solution. It is suggested that a possible increa se in pK(a) of HBrO3 in the reverse micelles requires a modified react ion scheme, which accounts for the observed dependency and explains wh y chemical oscillations can be observed in reverse micelles under unus ually high-pH conditions.