Mechanism of decomposition of peracetic acid by manganese ions and diethylenetriaminepentaacetic acid (DTPA) (original) (raw)
Related papers
Kinetics and mechanism of permanganate oxidation of nalidixic acid in aqueous alkaline medium
journal of applied pharmaceutical science, 2017
The kinetics and mechanism of oxidation of nalidixic acid (NA) by permanganate ion in alkaline medium have been studied at 40 ± 1 o C. The Stoichiometry was observed to be 2:1 in terms of mole ratio of permanganate ion and nalidixic acid consumed. The reaction shows first order with respect to oxidant and fractional order in both the substrate and alkali concentration. The oxidation reaction proceeds via an alkali permanganate species that forms a complex with nalidixic acid and the complex then decomposes to give the product. The effects of added products and ionic strength have also been investigated. The main products identified were hydroxylated NA and Mn(VI). A mechanism was proposed on the basis of experimental results. Investigation of the reaction at different temperature allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.
The intermediates in the permanganate oxidation of maleic and fumaric acids have been studied in acidic solutions, The accumulation and decay of manganese(ti1) has been demonstrated by the stopped-flow technique. The concomitant four-electron oxidation of the substrates leads to the formation of forrnyl( hydroxy)acetic acid. The subsequent reactions reveal a complex pattern in which hydroxymalonic. glyoxylic, and oxalic acid are further intermediates. The product distribution has been determined as a function of the pH and the mole ratio of the reactants. A reaction scheme is suggested which rationalises the observed behaviour.
Inorganic Chemistry, 2009
Herein, we report reactivity studies of the mononuclear water-soluble complex [Mn(II)(HPClNOL)(η 1 -NO 3 )(η 2 -NO 3 )] 1, where HPClNOL ) 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol, toward peroxides (H 2 O 2 and tertbutylhydroperoxide). Both the catalase (in aqueous solution) and peroxidase (in CH 3 CN) activities of 1 were evaluated using a range of techniques including electronic absorption spectroscopy, volumetry (kinetic studies), pH monitoring during H 2 O 2 disproportionation, electron paramagnetic resonance (EPR), electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS], and gas chromatography (GC). Electrochemical studies showed that 1 can be oxidized to Mn(III) and Mn(IV). The catalase-like activity of 1 was evaluated with and without pH control. The results show that the pH decreases when the reaction is performed in unbuffered media. Furthermore, the activity of 1 is greater in buffered than in unbuffered media, demonstrating that pH influences the activity of 1 toward H 2 O 2 . For the reaction of 1 with H 2 O 2 , EPR and ESI(+)-MS have led to the identification of the intermediate [Mn(III)Mn(IV)(µ-O) 2 (PClNOL) 2 ] + . The peroxidase activity of 1 was also evaluated by monitoring cyclohexane oxidation, using H 2 O 2 or tert-butylhydroperoxide as the terminal oxidants. Low yields (<7%) were obtained for H 2 O 2 , probably because it competes with 1 for the catalase-like activity. In contrast, using tert-butylhydroperoxide, up to 29% of cyclohexane conversion was obtained. A mechanistic model for the catalase activity of 1 that incorporates the observed lag phase in O 2 production, the pH variation, and the formation of a Mn(III)-(µ-O) 2 -Mn(IV) intermediate is proposed. (1) (a) Sies, H. Angew. Chem. 1986, 25, 1058-1071. (b) Doctrow, S. R.; Huffman, K.; Marcus, C. B.; Tocco, G.; Malfroy, E.; Adinolfi, C. A.; Kruk, H.; Baker, K.; Lazarowych, N.; Mascarenhas, J.; Malfroy, B.
2007
Natural terpenes, (-)-limonene and (+)-carvone, can be epoxidized by peroxyacetic acid (PAA) at room temperature if a dinuclear manganese(IV) complex with 1,4,7-trimethyl-1,4,7-triazacyclononane (L), [Mn 2 L 2 O 3 ] [PF 6 ] 2 , is used as a catalyst. The total yield of the epoxides based on the consumed olefins are 97 and 95%, respectively. A kinetic study of the dec-1-ene and cyclohexane oxygenations including the investigation of their simultaneous competitive oxidation was carried out. The olefin epoxidation rate does not depend on dec-1-ene concentration and the dec-1-ene concentration does not affect the rate of cyclohexane oxidation. The cyclohexane oxidation rate is proportional to the alkane concentration. The kinetic analysis led to the conclusion that two species X 1 and X 2 are generated in the system, and there is no their mutual interconversion. The rate equation for the dec-1-ene epoxidation was proposed: W = k +1 [cat][PAA], where cat is the initial manganese complex or its derivative, and the constant was determined: k +1 = 3.5 mol-1 dm 3 s-1. Species X 1 is apparently an effectively epoxidizing manganese peroxo derivative whereas species X 2 is an alkane hydroxylating manganese oxo complex.
Transition Metal Chemistry, 1989
The kinetics and mechanism of glutamic acid (GCO2H) oxidation by acid permanganate has been carried out in the absence and presence of sodium dodecyl sulphate (SDS). The surfactant enhances the reaction rate without changing the reaction mechanism. The overall rate expression for the reduction of Mn TM may be written:-d[MnW~]tot,~/dt = {k~f + k2f/[H +] } X [GCO 2 HI o [MnVlI]total. The reaction appears to involve parallel consecutive processes in which Mn Iv is formed as the reaction intermediate, k4f signifies the rate constant for the path leading to Mn ~v as intermediate, whereas kzf signifies the rate constant for the path leading to the reduction of Mn w~ to Mn II, without prior formation of Mn Iv. A mechanism satisfying the various kinetic parameters is proposed.
Kinetics andmechanism of oxidation of L-cysteic acid by permanganate ion in aqueous acidic medium
2012
Kinetics studies has been carried out on the oxidation of L-cysteicacid (HR'H) by permanganate ion in aqueous acidic medium at 27.0±1.00C, I= 0.5mol dm-3(Na2SO4), [H+] = 1.0´10-1mol dm-3.The stoichiometry of reaction was 2:5 (MnO4 - :HR'H). The reaction was also found to be first order in [MnO4 -] and [HR'H] respectively and the reactions conformed to the following rate law. The rate of reaction displayed negative salt effects. Added anions and cations catalysed the reaction and changes in dielectric constant of the medium had no effect on the rate of the reaction. The results of spectroscopic and kinetic investigation did not indicate intermediate complex formation during the course of the reaction, since there was no change in λmax at 525nm. The outer- sphere mechanism is proposed for these reactions.
Journal of Saudi Chemical Society, 2016
The kinetics of permanganate oxidation of two substituted azinylformamidines (Azn-Fs), namely N,N-dimethyl-N 0-(pyridin-2-yl)formamidine (Py) and N,N-dimethyl-N 0-(pyrimidin-2yl)formamidine (Pym), in sulfuric acid were investigated using conventional spectrophotometry. Kinetic evidence for the formation of 1:1 intermediate complexes between the oxidant and substrates was obtained. The reactions of both substrates with permanganate showed similar kinetics, i.e. first order in [MnO 4 À ] 0 and fractional-first-order with respect to both [Azn-F] 0 and [H + ]. The initial product, Mn 2+ , was found to autocatalyze the oxidation process. Changes in the ionic strength and dielectric constant of the medium had no significant effect on the rate. The final oxidation products of Py and Pym were identified as 2-aminopyridine and 2-aminopyrimidine, respectively, in addition to dimethylamine and carbon dioxide. A plausible reaction mechanism is suggested and the reaction constants involved in the mechanism were evaluated.
A Kinetic Study of the Reduction of Colloidal Manganese Dioxide by Oxalic Acid
Journal of Colloid and Interface Science, 1996
or reaction products in most permanganate oxidations (11, A kinetic study of the reaction between colloidal manganese 12), being actively involved in the mechanism as autocatadioxide and oxalic acid in aqueous acetate media (pH 4.3-5.1) is lysts in many cases (13, 14). reported. The reaction is autocatalytic and, in order to determine On the other hand, although the kinetic aspects of the the rate constants k 1 and k 2 corresponding, respectively, to the manganese-oxalate reacting systems have gained new internoncatalytic and autocatalytic reaction pathways, the Mn(III) est in the last decade due to their involvement in some oscilformed as an intermediate was stabilized by addition of sodium lating reactions (15-20), the reduction of colloidal mangapyrophosphate. Joint iodimetric and spectrophotometric studies nese dioxide by oxalic acid has received much little attention indicated that the reduction of colloidal manganese dioxide follows (21-23) than its relative, the permanganate-oxalate reacthe sequence tion (24, 25). We have now undertaken a kinetic study of the reaction between colloidal manganese dioxide (in the form of a perfectly transparent, aqueous sol) and oxalic acid and found that it is in fact an autocatalytic reaction, whose Mn(IV) r R Mn(II) Mn(IV) Mn(III) r R Mn(II), where R stands for the reductant. Both reaction pathways exhibit stoichiometry may be written as acid catalysis, and the activation energies associated to k 1 and k 2 are 74.7 { 0.9 and 44.6 { 0.6 kJ mol 01 , respectively. The reaction
Oxidation of Nicotinate Ion by Heptavalent Manganese: a Kinetic and Mechanistic Approach
Zeitschrift für Physikalische Chemie, 2003
The kinetics of oxidation of nicotinate ion by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate and nicotinate ion in alkaline medium exhibits 2 : 1 stoichiometry KMnO4 : Nicotinate ion). The reaction shows first order dependence of rate on permanganate concentration and less than unit order dependence each in nicotinate ion and alkali concentrations. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the formation of an intermediate complex between oxidant and substrate has been proposed. The rate and the activation parameters for the slow step have been evaluated.