Stoichiometry of bromide production from ceric oxidation of bromomalonic acid in the Belousov-Zhabotinskii reaction

Abstract

We investigated the number of Ce4+ ions required to produce one Br-ion in the oxidation of bromomalonic acid by Ce4+ under conditions appropriate tg the oscillating Belousov-Zhabotinskii (BZ) reaction. We found a ratio of 1 : 1, in agreement with earlier results by Jwo and Noyes (J. Am. Chem. SOC. 1975, 97, 5422), in the presence of oxygen. With oxygen excluded from the system, we found a ratio of 2:l. The presence of malonic acid in the system had no effect on the bromide production, contrary to the assumption of recent theoretical models of the Belousov-Zhabotinskii reaction.

Role of Dibromomalonic Acid in the Photosensitivity of the Ru(bpy)32+-Catalyzed Belousov−Zhabotinsky Reaction

“…This process may be written as The reduction of Ru(III) in a large excess of bromide follows an exponential rate law, which gives k 17 …”

“…According to Försterling,17,18 the concentration of Br 2 MA can be quite high if the sum of the initial bromide and bromate concentrations is comparable with [MA]. This situation occurs in many pattern formation experiments.…”

Experimental and mechanistic study of the bromomalonic acid/bromate oscillating system catalyzed by [Fe(phen)3]2+

“…Bromomalonic acid was prepared as dipotassium salt following the procedure described by Försterling et al [20]. The purified product presents the same NMR 13 C spectrum reported in article [20].…”

“…The purified product presents the same NMR 13 C spectrum reported in article [20]. Sodium bromate (Merck), 1,10-ortophenantroline (Merck), and ammonium iron(II) sulfate hexahydrate (Merck) were used without further purification.…”

“…Fe(phen) 3 et al [20] have shown that the in situ [19] bromination of malonic acid gives a mixture of MA, BrMA, and dibromomalonic acid (Br 2 MA) with a more or less low content of bromomalonic acid. In addition, it is possible that the Oregonator approximation [5] in which a stoichiometric factor q connects the Br Ϫ production with the oxidized catalyst consumption cannot adequately model the peculiarities of the Br Ϫ ion concentration behavior.…”