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The work pertains to the study on direct and indirect interaction of a macroporous weak acid cation exchange resin‐Dowex Mac 3H form with Belousov‐Zhabotinsky (BZ) reaction based on malonic acid‐cerium‐bromate‐sulfuric acid system. In the direct mode, the above reaction was perturbed by adding 10% (w/w) of Dowex Mac 3H at three different time intervals, i. e., before the start of induction period, during the induction period and after the commencement of oscillations. This mode of interaction was studied to investigate the effect of heterogeneity on the dynamics of BZ reaction. The indirect interaction of the resin was studied by interacting the resin individually with the optimized metal catalyst for a particular period of time after which the supernatant was used as initial reagent in the otherwise optimized BZ system. The interaction was monitored with respect to the change in oscillatory parameters before and after loading the resin with metal catalyst. The selectivity of the resin towards cerium and iron (ferroin) was studied through the said BZ reaction using potentiometry as the main technique. It was found that resin is more selective towards ferroin. The selectivity of the resin towards the various metal ions was followed by their estimation using UV‐Visible spectrophotometry. The effect of solvents on the ion exchange capacity (IEC) of the resin was also studied through the BZ reaction. Some solvents increased its IEC while others decreased it. The potentiometric results obtained were validated by spectroscopic findings and electrochemical studies. [ABSTRACT FROM AUTHOR]

Abstract: Effect on the behavior of Tyrosine through a malonic acid (MA) based Briggs‐Rauscher (BR) oscillatory system was studied in order to understand the mechanistic details of thyroid metabolism in vitro, specifically the iodination of tyrosine. It was observed that the present BR system employing tyrosine as a main additive and malonic acid as substrate provides an example of entrainment oscillations, in which malonic acid is responsible for oscillations and in presence of tyrosine, the system showed different oscillatory behavior. The effects of various other chemical species such as SeO2, KSCN, KNO3, KBr and Fe(III) on the tyrosine in this malonic acid based BR system are studied. The study was supported by UV‐Visible spectrophotometry to study the interactions of these chemical species with Dushmann reaction, which is one of the important reaction steps in BR reaction mechanism, in order to investigate the key factors responsible for tyrosine iodination responsible for thyroxin formation. Needless to mention that, all the aforesaid chemical species have due role in normal thyroid metabolism in vivo and as such, the present BR system containing tyrosine as main (first) additive can help in understanding of thyroid metabolism. [ABSTRACT FROM AUTHOR]

ABSTRACT The response of the Ce(III)-catalyzed phloroglucinol (1,3,5-trihydroxybenzene)-based Belousov Zhabotinsky system to the addition of various antioxidants (ascorbic acid, glutathione, inosine, N-acetylcysteine) is monitored at 30°C under stirred batch conditions. This method is convenient and has good sensitivity for the determination of these antioxidants. The addition of these antioxidants to the BZ mixture influences the oscillatory parameter (number of oscillations) to an extent that depends on the concentration of the antioxidant. The experimental results have shown that the number of oscillations decrease on increasing the concentration of antioxidant. The calibration plots show a linear relationship ( R2 = 0.98 for ascorbic acid and glutathione and R2 = 0.99 for inosine and N-acetylcysteine) between the number of oscillations and the [antioxidant] over the concentration range of 0.0125-0.5, 0.05-0.2, 0.025-0.1, and 0.1-0.5 mol L−1 with detection limits 6.9 × 10−5, 2.762 × 10−4, 1.381 × 10−4, and 5.524 × 10−4 mol L−1 for ascorbic acid, glutathione, inosine, and N-acetylcysteine, respectively. Some aspects of the mechanism of these antioxidants on the BZ system have been discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT Kinetic studies on the Belousov-Zhabotinsky (BZ) system with various metal ions as catalysts have been carried out for a long time, but the effect of counteranions associated with the metal ion solution used as the catalyst in the BZ reaction has not been explored. Thus, we have chosen some metal salts as catalysts having the metal ion (Mn n+) but with various anions to study the role of different anionic moieties of catalyst on the oscillatory behavior of the resorcinol-based BZ reaction system. It is found that organic-type anionic moieties marginalize the role of organic substrates in the reaction system. On the other hand, the inorganic counterions of the catalyst show salting out effects, thereby increasing the ionic strength, which affects the mobility (diffusion) of the ions in our system performed under batch conditions. [ABSTRACT FROM AUTHOR]

The present investigation pertains to the kinetic study on bromate-driven and manganese ion catalyzed Belousov-Zhabotinsky oscillatory chemical reaction having catechol (1,2-dihydroxybenzene) as the organic substrate in aqueous acid media at 30 ± 0.1oC under stirred conditions. Although some polyphenols as chemical oscillators are known in the literature but the role of catechol has been marginalized. The reaction system with catechol shows long-time series of periodic as well as aperiodic oscillations, which were monitored potentiometrically in the oxidation reduction potential (ORP) mode under batch conditions. The various oscillatory parameters such as induction time ( tin), time period ( tp), amplitude ( A), and number of oscillations ( N) were obtained by drawing a plot between redox potential (mV) versus time (s). It is found that the oscillatory parameters of the system vary with the concentration of the reacting species. The reaction system was also studied in different aqueous acid media, but the detailed studies with respect to experimental parameters have been made in aqueous sulfuric acid medium as it showed a broad oscillatory window and better oscillatory characteristics. Moreover, the oscillatory parameters in general and induction time in particular vary significantly with temperature (15 to 45 ± 0.1oC). The activation parameters of the system have also been calculated. The oscillatory behavior of the reaction system was also confirmed spectrophotometrically. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 141-151, 2013 [ABSTRACT FROM AUTHOR]

The present work pertains to the effect of temperature on the oscillatory behavior of bromate driven, Manganese (II) ion catalyzed BZ reaction with aromatic substrate i.e. resorcinol under batch conditions in 1.3 M sulfuric acid as aqueous acid medium. In order to study the effect of methyl ketones as additives (co-substrates), acetone is added to the aforesaid reaction system and the oscillations of the mixed substrate systems were studied at different temperatures. Further the effect of temperature with respect to ternary systems comprising of acetone with other ketones like butanone, pentanone, hexanone and acetyl acetone in 1:1 (v/v) ratio is also studied. It is found that temperature has a marked influence on the reactivity of the reaction systems, with and without methyl ketones and at all concentrations of the additives. Moreover, the rate of enolization of ketones also affects the oscillatory parameters like tin and tp. Although the exact values of enolization constants for the methyl ketones are not known to us, but by studying the oscillatory behavior, a trend can be predicted. Further the formation of end products in the ternary systems is influenced due to hydrophobic interactions of the ketones. [ABSTRACT FROM AUTHOR]

A detailed investigation on resorcinol as the Belousov–Zhabotinsky (BZ) oscillator in manganese(II) ion catalyzed reaction system with inorganic bromate (oxidant) and acetone (cosubstrate) was carried out in aqueous sulfuric acid medium (1.3 M). The aforesaid reagents were mixed with various concentrations to evolve the effective concentrations at which the reaction system exhibited better oscillations. The various oscillatory parameters such as time period (tp), induction period (tin), frequency (v), amplitude (A), and number of oscillations (n) were derived, and the dependence of concentration of the reacting species on these oscillatory parameters was interpreted on the basis of the Field–Koros–Noyes mechanism. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 650–657, 2009 [ABSTRACT FROM AUTHOR]