Perturbation of the Oscillatory BZ Reaction with Methanol and Ethylene Glycol:  Experiments and Model Calculations

Abstract

This study is initiated by a recent discovery, according to which a water soluble polymer, poly(ethylene glycol) (PEG), affects the dynamics of the Belousov-Zhabotinsky (BZ) reaction in a characteristic way. As various polymers and polymer-based hydrogels are often applied in nonlinear chemical experiments, it is an interesting question whether the effect of a polymer can be attributed exclusively to its reactive endgroups (here primary alcoholic groups) or if the macromolecular nature of the perturbant might be also important. In this paper, as a first step, the results of batch experiments are presented applying only small molecules, namely ethylene glycol (the monomer of PEG) and methanol (a more simple primary alcohol), as perturbants of the BZ reaction. The reaction was followed by monitoring the rate of the carbon dioxide evolution. The experimental results are compared with model calculations, applying the latest model of the BZ reaction, the Marburg-Budapest-Missoula (MBM) mechanism extended with the perturbing reactions. The rate of the perturbing reactions (reaction of the acidic bromate with the alcohol producing the autocatalytic intermediate bromous acid) was determined in separate spectrophotometric experiments. Experiments and model calculations show a good qualitative agreement (alcoholic perturbations increase the induction period and the frequency of the oscillations and decrease the amplitude), but disagreements were found on a quantitative level. Because the mechanism of the alcoholic perturbation, especially in the case of methanol, is mostly clarified, it is the MBM mechanism which should be modified somewhat in the future. As the reaction dynamics responds to the alcoholic perturbations rather sensitively, simulating these perturbation experiments can help to test new mechanistic proposals for the BZ reaction.

Dynamic evolution of the oscillatory Belousov–Zhabotinsky reaction upon addition of a non-ionic polymer

“…These reactions are also analogous to those [3] proposed for the aliphatic alcohols and ethyleneglycol and justify the overproduction of BrO Å 2 . This way the system necessitates a longer time to accumulate a sufficient amount of BrMA in order to turn off the autocatalytic reaction.…”

“…Numerous attempt have been made to elucidate the very complicated chemical reaction mechanism [2][3][4] and, in addition, peculiar features have been detected by performing the BZ reaction in nanostructured systems [5][6][7][8]. It is worth to remember that in the BZ reaction there are several species, and among them radicals, the concentration of which (very low) oscillates with time.…”

Nonlinear Response of a Batch BZ Oscillator to the Addition of the Anionic Surfactant Sodium Dodecyl Sulfate

“…Among the model systems that have attracted the attention of researchers, the oscillating reaction of Belousov-Zhabotinsky (BZ) is one of the most extensively studied. [1][2][3][4][5][6][7] In fact, the first study was undertaken in order to mimic the Krebs cycle. In its "classic" version, the BZ reaction consists of the bromuration and oxidation of an organic substrate (the malonic acid) in strongly acidic medium, in the presence of a catalyst (one electron redox couple, usually the system Ce(IV)/Ce(III) or Ferroin/Ferriin).…”

Influence of Micellar Propinquity on Dynamics of Ce(IV)‐Catalyzed BZ Oscillatory Reaction under Stirred Conditions

“…The experimental observations reveal that the presence of the OH group containing perturbants in general leads to variation of oscillation parameters by active participation in a reaction network . The involvement of OH groups in the BZ reaction has been confirmed by the addition of methanol and ethylene glycol to the BZ system . Therefore, the impact of Brij58 on dynamics of the BZ reaction could be explained by taking into account reactions of terminal OH groups.…”