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Reaction rates have been measured in acid solution at 25 OC for several reactions of iodine species and hydrogen peroxide. The reactions are all subsystems of reactions which occur in iodate-hydrogen peroxide oscillators. Reactions discussed are the following: HOI + HOI -HOIO + H+ + I-, -'/,d[HOI]/dt = 25 * 5 M-' s-'[HOII2; HOI + HOIO -2H+ + I-& 0.2 s-'[HOIO]~/[H+]; HOI + H202 -H+ + I-+ O2 + H20, -d[HOI]/dt = 5 & 3 M-' s-'[HOI] [H202]. In addition, reaction products have been studied for reaction of H20z with HOI and HOIO. In both cases, at [H'] -0.1 M, oxidation to IO3-is predominant at low [H202]. Rates are too fast to establish rate laws by using manual mixing techniques. Calculations for a skeleton model of the Briggs-Rauscher oscillator, using the above rate constants, reproduce basic experimentally observed features. + IO3-, -d[HOI]/dt = 230 & 20 M-' s-'[HOI][HOIO]; HOIO + HOIO -H+ + IO3-+ HOI, -'/2d[HOIO]/dt = 0.3

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Several new organic substrates have been found to promote oscillations in batch conditions in the Briggs−Rauscher oscillating system. The new substrates, crotonic acid, acrylic acid, anisole, and p-nitrophenol, react with iodine (I) by either addition or substitution reactions. Rate constants for reactions of these four compounds with HOI have been determined. Previously known substrates have active methylene hydrogens and react with I2 via an enol mechanism. Some type of active reduction of HIO2 to HOI (other than by iodide) must be included in the mechanism to allow the simulation of oscillations with the new substrates.