Influence of Visible Light and Malonic Acid Derivatives on the Autocatalytic Oxidation of Ru(II) by Bromate Ions

Abstract

The influence of visible light on the autocatalytic oxidation of Ru(II) by bromate ions has been investigated. The inflection time (IT) was measured in darkness, at constant illumination, or as a function of the length of a perturbing light pulse. Measurements were performed without organic substrate, as well as in the presence of the malonic acid derivatives HOOC-CHR-COOH (RMA), with R being H, methyl-, ethyl-, n-butyl-, or the benzyl-group. The presence of RMA influences the length of the inflection time in darkness and for light-perturbed conditions. In the presence of benzylmalonic acid (BzMA), small amplitude oscillations are observed in darkness at the end of the autocatalytic oxidation of Ru(II). The most pregnant effects of RMA are observed by malonic acid (MA). At constant illumination, the inflection time is found to increase with increasing MA concentration and small-amplitude oscillations can even be observed in the preexponential phase of the Ru(II) oxidation. Model calculations based on a modified Noyes-Field-Thompson mechanism are in accordance with experimental observations. The calculations suggest that the small-amplitude oscillations observed in the BzMA and MA systems are due to second-order organic radical recombination.

Complex Dynamical Behavior in the Highly Photosensitive Cerium–Bromate–1,4-Benzoquinone Reaction

“…Reactions between bromate and organic substrates in an acidic solution with or without the assistance of metal catalysts have been extensively investigated in the context of nonlinear chemical dynamics in which the overall process can be characterized as the oxidation and bromination of the organic substrate. − The frequently employed catalysts include ferroin, ruthenium complexes, cerium, and manganese. , The oxidation of the substrate, taking place through its reaction with the oxidized catalyst, − is largely responsible for the regeneration of the reduced metal catalysts for the autocatalytic processes. The recycling of the metal catalysts ensures that continuous oscillations can exist in bromate-based chemical oscillators such as the Belousov–Zhabotinsky (BZ) oscillator.…”

Complex kinetics and significant influences of bromine removal in ferroin–bromate–metol reaction

“…Since the discovery of the Belousov-Zhabotinsky (BZ) reaction, [1][2][3] a large family of bromate-based chemical oscillators have been uncovered over the past three decades, including both catalyzed and uncatalyzed systems. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The majority of those bromate oscillators are the replacement of malonic acid of the BZ reaction by different organic substrates. [7][8][9][10][11][12][13][14][15][16][17][18] When malonic acid is replaced, the consumption rate of bromine molecules and the production paths of bromide ions, that modulate the autocatalytic feedback cycles, are alternated.…”

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The majority of those bromate oscillators are the replacement of malonic acid of the BZ reaction by different organic substrates. [7][8][9][10][11][12][13][14][15][16][17][18] When malonic acid is replaced, the consumption rate of bromine molecules and the production paths of bromide ions, that modulate the autocatalytic feedback cycles, are alternated. 19 As a result, those modified BZ systems may exhibit very different reaction behavior.…”