Kinetic study of the Ce(III)-, Mn(II)- or Fe(phen)32+-catalyzed Belousov-Zhabotinsky reaction with ethyl hydrogen malonate

Abstract

In a stirred batch reaction, Fe(phen) 3 2ϩ ion behaves differently from Ce(III) or Mn(II) ion in catalyzing the bromate-driven oscillating reaction with ethyl hydrogen malonate [CH 2 COOHCOOEt, ethyl hydrogen malonate (EHM)]. The effects of N 2 atmosphere, concentrations of bromate ion, EHM, metal ion catalyst, sulfuric acid, and additive (bromide ion or bromomalonic acid) on the pattern of oscillations were investigated. The kinetic study of the reaction of EHM with Ce(IV), Mn(III), or Fe(phen) 3 3ϩ ion indicates that under aerobic or anaerobic conditions the order of reactivity toward reacting with EHM is Mn(III) Ͼ Ce(IV) Ͼ Ͼ Fe(phen) 3 3ϩ , which follows the same trend as that of the malonic acid system. The presence of the ester group in EHM lowers the reactivity of the two methylene hydrogen atoms toward bromination or oxidation by Ce(IV), Mn(III), or Fe(phen) 3 3ϩ ion. No good oscillations were observed for the BrO 3--CH 2 (COOEt) 2 reaction catalyzed by Ce(III), Mn(II), or Fe(phen) 3 2ϩ ion.

Measurements and Simulations of the Acidity Dependence of the Kinetics of the Iron-Catalyzed Belousov–Zhabotinsky Reaction: Proton-Catalysis in the Electron Transfer Reaction Involving the [Fe(phen)3]3+ Species

“…Smoes first studied the effects of the initial sulfuric acid concentration on the period time of the iron-catalyzed BZ reaction and showed that the period time decreases exponentially with increasing acidity in the range 0.3–1.4 mol L –1 H 2 SO 4 . A decrease in the period time with increasing acidity was also reported for the cerium-catalyzed reaction by Misra et al with initial H 2 SO 4 concentrations up to 4.0 mol L –1 and by Hsu and Jwo in the acidity range 0.5–1.5 mol L –1 H 2 SO 4 . The acid dependence usually has been associated with the bromine chemistry of reactions R1–R5.…”

Mechanism and Phenomenology of an Oscillating Chemical Reaction

“…The reaction products were found to be BrMeMA and acetic acid (AcA), in the ratio 2:3 respectively, exactly as was predicted by FKN for MA. Jwo and others have investigated the kinetics of ethyl-, butyl-, phenyl-malonic acids, and many similar species [79][80][81][82][83]. These acids are less reactive than MA with Ce 4+ , and typically form less reaction products.…”