Micellar Effects on the Kinetics of Cerium(IV) Oxidation and the Cerium(IV)-Catalyzed Belousov−Zhabotinsky Reaction with Methyl-, Ethyl-, or Benzylmalonic Acid

Abstract

The kinetics of the oxidation of methyl- (MeMA), ethyl- (EtMA), or benzylmalonic (BzMA) acid by ceric ions and the Ce(IV)-catalyzed Belousov−Zhabotinsky (BZ) reaction with these substrates have been studied at 20.0 °C in stirred batch conditions in the absence and the presence of the cationic surfactant cetyltrimethylammonium nitrate (CTAN). Some measurements have also been performed using the anionic surfactant sodium dodecyl sulfate (SDS). Addition of increasing amounts of CTAN has a little inhibitory influence on the redox process with MeMA and EtMA, whereas it causes a significant enhancement with BzMA. Small decreasing rate effects are observed in the presence of SDS. In the absence of surfactants, the BZ systems with MeMA and EtMA show oscillatory behavior after an induction period, whereas no oscillations are found with BzMA. In the presence of CTAN all the systems exhibit oscillations after an induction period that is shortened markedly with increasing CTAN concentration and that, at constant [CTAN], increases in the order BzMA < MeMA < EtMA. Added CTAN also affects the oscillation period and the duration of the raising portion of an oscillatory cycle. The surfactant SDS affects these oscillatory parameters to a different extent. Explanations of the experimental results are provided.

Electrochemical redox processes involving soluble cerium species

“…The Ce(III)/Ce(IV) redox couple also participates in the Belousov-Zhabotinsky oscillating reaction via autocatalytic oxidation [229,230]. Efforts have been devoted to further study the effects and kinetics of cerium in such complex reaction mechanisms [231][232][233][234][235], including the reaction mechanism with malonic acid [236,237].…”

Effect of self-assemblies of various surfactants in their single and mixed states on the BZ oscillatory reaction

“…Changes in the external environment of an oscillatory chemical reaction by application of electric field, magnetic field, or light can be used to control its dynamics [13][14][15]. Control can also be achieved internally by performing the reaction in the presence of nonreacting chemical species such as micelles [16][17][18][19] known to affect chemical equilibria and reactivities [20,21] by selectively sequestering the reagent substrates by means of electrostatic and hydrophobic interactions. Investigating the influence of micelle-forming surfactants on the BZ oscillatory reactions [22][23][24] has received growing attention not only for the attempt to elucidate their complex mechanism [4,25] but also for their relevance to the periodic phenomena in biochemical systems [26].…”

“…Investigating the influence of micelle-forming surfactants on the BZ oscillatory reactions [22][23][24] has received growing attention not only for the attempt to elucidate their complex mechanism [4,25] but also for their relevance to the periodic phenomena in biochemical systems [26]. It has been shown by different workers that micelles affect different parameters of the BZ oscillatory reaction such as induction period (IP), oscillation time period, and so on while treating the micelles as nonreactive [16][17][18][27][28][29][30][31].…”

Role of surfactants on metal mediated cerium(IV) oxidation of valeraldehyde at room temperature and pressure

“…The final reaction products are obtained by the subsequent fast oxidation of the organic radical. This type of mechanism has been proposed previously [17,34,39] the oxidation of a variety of organic substrates by cerium(IV) in sulfuric acidic media. The kinetics of the forgoing reactions were studied and showed that substrates and oxidant interact in an equilibrium step to form an intermediate complex which is assumed to disproportionate forming a free radical and reduced Ce(IV).…”