Oscillating reactions are known for the complexity of their mechanisms. One aid in unraveling these complexities is model reduction. We have reinvestigated a mechanism of the bromite-iodide reaction, which is a subsystem of the bromate-iodide reaction, a clock reaction whose rate law is determined in a well-known general chemistry laboratory experiment. We have developed several reduced models via sensitivity analysis, all of which retain clock behavior as a distinctive feature. For the bromite-iodide reaction, we define clock behavior as depletion of I− and a lagging increase in one or both of [HOI] and [HOBr]. Here we analyze the clock behavior at pH 6 to 8 under conditions of excess bromite and at pH 5.7 over a range of [Br(III)]0/[I−]0 ratios. Reduced models were created by eliminating redundant species, where a redundant species is defined as one for which clock behavior is preserved in the absence of that species. BrO−, IO−, and HOIO are redundant when any one of these species is treated as being unreactive. Clock behavior persists for a diminished range of conditions when pairs of these species or all three species are eliminated, making redundancy ambiguous. Such ambiguities notwithstanding, clock behavior is maintained over a wide range of conditions, even when all three species are removed.

Sensitivity analysis and model reduction of a mechanism for the bromite-iodide reaction

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