Oxidation of thiourea by iodate: a new type of oligo-oscillatory reaction

Rábai, Gyula; Beck, M. T.

doi:10.1039/dt9850001669

Cited by 41 publications

(57 citation statements)

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“…The oxidation products may be urea, disulfide, and, in some cases, it may undergo either oxidative cyclization or degradation. Oxidation of thiourea by iodate (40), chlorite (41), and bromate (42) has been found to give complex kinetic behavior. With iodate, the reaction displays oligo-oscillation, in which the concentration of iodide goes through several maxima in a single reaction (40).…”

Section: Oxidation Of Thioureamentioning

confidence: 99%

Oxidation of thiourea and substituted thioureas: a review

Sahu

Sahoo

Patel

et al. 2011

Journal of Sulfur Chemistry

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Section: Oxidation Of Thioureamentioning

confidence: 99%

Oxidation of thiourea and substituted thioureas: a review

Sahu

Sahoo

Patel

et al. 2011

Journal of Sulfur Chemistry

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“…Progress has been made on the mechanisms of the oxidation of thiourea itself [8,12], but these mechanisms have not been able to explain the dynamics observed with substituted thioureas. The oligooscillatory behavior observed with iodate has not yet been completely explained [11].…”

Section: Introductionmentioning

confidence: 98%

“…Part of our interest in thioureas is derived from the observation that their oxidation by a variety of oxidants always yields exotic or nonlinear dynamic behavior [10]. For example, the oxidation of thiourea by chlorite [8], iodate [11], and bromate [12] yields clock reaction characteristics. With chlorite [8] one observes, after some quiescent induction period, that there is a sudden and rapid production of chlorine dioxide followed by an equally rapid production of H ϩ ions.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear dynamics in the oxidations of substituted thioureas I: The reaction of 4-methyl-3-thiosemicarbazide with acidic iodate [1]

Mundoma

Simoyi

2000

Int. J. Chem. Kinet.

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The substituted thiourea, 4-methyl-3-thiosemicarbazide, was oxidized by iodate in acidic medium. In high acid concentrations and in stoichiometric excess of iodate, the reaction displays an induction period followed by the formation of aqueous iodine. In stoichiometric excess of methylthiosemicarbazide and high acid concentration, the reaction shows a transient formation of aqueous iodine. The stoichiometry of the reaction is:. Iodine formation is due to the Dushman reaction that produces iodine from iodide formed from the reduction of iodate:. Transient iodine formation is due to the efficient acid catalysis of the Dushman reaction. The iodine produced in process B is consumed by the methylthiosemicarbazide substrate. The direct reaction of iodine and methylthiosemicarbazide was also studied. It has a stoichiometry of 4I 2 (aq) ϩ CH 3 NHC (" S)NHNH 2 ϩ 5H 2 O :The reaction exhibits autoinhibition by iodide and acid. Inhibition by I Ϫ is due to the formation of the triiodide species, I 3 Ϫ , and inhibition by acid is due to the protonation of the sulfur center that deactivates it to further electrophilic attack. In excess iodate conditions, the stoichiometry of the reaction is 8IO 3 Ϫ ϩ 5CH 3 NHC("S)NHNH 2 ϩ H 2 O : 4I 2 ϩ 5SO 4 2Ϫ ϩ 5CH 3 NHC("O)NHNH 2 ϩ 2H ϩ (D) that is a linear combination of processes A and B.

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“…Similar reactions of the oxidation of thiourea by bromate in acidic solution was studied by Simoyi et al 9 and found that the mechanism requires the cleavage of the X-C bond to form urea and SO 4 2-.The oxidation of thiourea by iodate, a new type of oligo oscillatory reaction was studied 10 where the end products are sulphate ions, ammonium ions and carbon dioxide. Kinetics of the chromium(VI) by thiourea reaction in the presence of polyacrylamide was reported by Southard et al 11 .…”

Section: Introductionmentioning

confidence: 99%

Kinetic, Mechanistic and Spectrophotometric Study of Micelle Effects on the Oxidation of Thiourea by Quinolinium Dichromate in Perchloric Acid Medium

2013

Chem Sci Trans

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Abstract:The kinetic investigation of oxidation of thiourea by quinolinium dichromate (QDC) in perchloric acid medium at constant ionic strength was studied spectrophotometrically at 440 nm. A stoichiometric ratio of 3:1 with thiourea versus QDC was observed. The reaction was first order with respect to thiourea, monomeric QDC (QMC) and HClO 4 . Induced polymerization of acrylonitrile was observed. The mechanism involved the attack of protonated monomeric QDC (QMC) on the substrate in the rate determining step forming the products. Addition of Mn(II) has no effect on the reaction rate. The effect of anionic micelle (SDS) and neutral micelle (TX-100) on the system was studied using Berezin's kinetic model and observed a partial inhibitory effect on the rate of the reaction. The thermodynamic parameters like ∆E a ∆S and ∆G have been calculated and possible mechanism was proposed.

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Oxidation of thiourea by iodate: a new type of oligo-oscillatory reaction

Cited by 41 publications

References 0 publications

Oxidation of thiourea and substituted thioureas: a review

Oxidation of thiourea and substituted thioureas: a review

Nonlinear dynamics in the oxidations of substituted thioureas I: The reaction of 4-methyl-3-thiosemicarbazide with acidic iodate [1]

Kinetic, Mechanistic and Spectrophotometric Study of Micelle Effects on the Oxidation of Thiourea by Quinolinium Dichromate in Perchloric Acid Medium

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