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

Abstract

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 ].

Anomalous Dispersion and Attractive Pulse Interaction in the 1,4-Cyclohexanedione Belousov−Zhabotinsky Reaction

“…At large distances, this velocity gradient is nearly zero, and hence, no significant wave acceleration is observed Several earlier studies were dedicated to the identification of intermediate species and products in the reaction of 1,4-CHD with acidic bromate. 44, 45 It was found that 1,4-dihydroxybenzene (H 2 Q) is formed and further oxidized and brominated to 1,4-benzoquinone and bromoorganics. Szalai et al pointed out the importance of the rather stable oxidation product H 2 Q, which is produced continuously but oxidized in an autocatalytic fashion.…”

“…Szalai et al pointed out the importance of the rather stable oxidation product H 2 Q, which is produced continuously but oxidized in an autocatalytic fashion. 45,46 In contrast to the intensively studied CHD UBO, little is known about the CHD-BZ mechanism and its dynamic behavior. The latter one is more complex because it involves additional reaction such as the ones between CHD, H 2 Q, HBrO 2 , and ferriin.…”

Easy to use program “Simkine3” for simulating kinetic profiles of multi-step chemical Systems and optimisation of predictable rate coefficients therein

“…To show the versatility of the 'Simkine3' program, a complex 19-step mechanism scheme, which was proposed for the oxidation of the heterocyclic phenazine dye, methylene voilet (MV + ) by bromate ion acidic conditions is chosen [26,27].…”

Propagating Spiral Waves Obtained in a Catalyst-Immobilized Gel Membrane by the Belousov-Zhabotinsky Reaction System

“…22 The absence of gas production makes this system an attractive candidate for investigating chemical wave formation. [22][23][24][25][26] Another interesting and dynamic feature of bromate-1,4-cyclohexanedione-ferroin oscillating reaction is its complicated response to illumination. Kurin-Csörgei et al reported that illumination with moderate intensity results in an increase in frequency of oscillations and wave speed in bromate-1,4-cyclohexanedione-ferroin reaction; however, stronger illumination eliminates wave activity.…”