title: Reaction routes leading to CO2 and CO in the Briggs-Rauscher oscillator: analogies between the oscillatory BR and BZ reactions.
abstract: With Fenton-type experiments, it is shown that the intense CO2/CO evolution in the Briggs-Rauscher (BR) reaction is due to decarboxylation/decarbonylation of organic free radicals. The metal ion applied in the Fenton-type experiments was Fe2+ or Ti3+ or Mn2+ combined with H2O2 or S2O(8)(2-) as a peroxide, whereas the organic substrate was malonic acid (MA) or a 1:1 mixture of MA and iodomalonic acid (IMA). Experiments with a complete BR system applying MA or the MA/IMA mixture indicate that practically all CO2 and CO comes from IMA. The decarboxylation/decarbonylation mechanisms of various iodomalonyl radicals can be analogous to that of the bromomalonyl radicals studied already in the Belousov-Zhabotinsky (BZ) reaction. It is found that an intense CO2/CO evolution requires the simultaneous presence of H2O2, IO3-, Mn2+, and IMA. It is suggested that the critical first step of this complex reaction takes place in the coordination sphere of Mn2+. That first step can initiate a chain reaction where organic and hydroperoxyl radicals are the chain carriers. A chain reaction was already found in a BZ oscillator as well. Therefore, the analogies between the BR and BZ oscillators are due to the fact that in both mechanisms, free radicals and, in most cases, also transition-metal complexes play an important role.
authors.affiliation: Department of Physical Chemistry, Babes-Bolyai University, RO-400028 Cluj-Napoca, Romania.
authors.forename: Norbert
authors.initials: N
authors.lastname: Muntean
authors.forename: Gabriella
authors.initials: G
authors.lastname: Szabó
authors.forename: Maria
authors.initials: M
authors.lastname: Wittmann
authors.forename: Thuy
authors.initials: T
authors.lastname: Lawson
authors.forename: János
authors.initials: J
authors.lastname: Fülöp
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Noszticzius
authors.forename: Lavinia
authors.initials: L
authors.lastname: Onel