The 1,4-Cyclohexanedione−Bromate−Acid Oscillatory System. 3. Detailed Mechanism

1,4-Cyclohexanedione (CHD) in its reaction with acidic bromate undergoes aromatization and one of the main resulting products 1,4-dihydroxybenzene (H2Q) is further oxidized and brominated to 1,4-benzoquinone and bromoorganics. The kinetics of H2Q formation, of the reaction of CHD and Br2, as well as of the reaction between H2Q and bromate ion, were followed spectrophotometrically. The latter reaction exhibited Landolt (clock)-type dynamics. On the basis of our earlier analytical and present kinetic investigations, a detailed mechanistic model has been suggested that could well simulate the temporal oscillations of the title system. H2Q plays an essential role in the mechanism and is responsible for the unusual behavior (200−300 oscillations) of this chemical oscillator. We pointed to the relation that may exist between the CHD−bromate−acid system and those reported as oscillatory Landolt-type reactions [e.g., I − S − Fe(CN ].