Oxidation of hydrocarbons. 14.Autocatalysis during the oxidation of 1-tetradecene by methyltributylammonium permanganate

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An iodimetric technique has been developed to quantitatively analyze the oxidants present in organic solutions. Addition of excess tetrabutylammonium iodide and excess glacial acetic acid results in the formation of tetrabutylammonium triiodide, whose concentration can be measured spectrophotometrically at 295 or 365 nm. Application of this technique to the determination of the final oxidation state of manganese in permanganate reactions in methylene chloride solutions is described. The equilibrium constant for formation of tetrabutylammonium triiodide in methylene chloride has been measured: K = (3.48 -f 0.12) x lo4 at 25.0°C.Key words: iodimetric determinations, manganese oxidation states, methylene chloride, quaternary ammonium permanganate, quaternary ammonium triiodide. [Traduit par la revue]

Section: Introductionmentioning

confidence: 99%

Iodimetric determinations in organic solvents: Determination of manganese oxidation states in methylene chloride solutions

Perez‐Benito¹,

Brillas²,

Arias³

1990

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“…Although a kinetic study concerning the same reaction 1 has already been reported ( 6 ) , it deals exclusively with very i acid media and does not provide thorough information as far as the catalytic reaction pathway is concerned. The occurrence of autocatalysis in permanganate reactions appears to be extensive (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). In particular, the permanganate oxidation of amines (22)(23)(24)(25) deserves special mention…”

Section: Introductionmentioning

confidence: 99%

Permanganate oxidation of glycine: Kinetics, catalytic effects, and mechanisms

Perez‐Benito¹,

Mata-Pérez²,

Brillas³

1987

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. J . Chem. 65, 2329Chem. 65, (1987.The oxidation of glycine by permanganate ion in aqueous phosphate buffers is autocatalyzed by the soluble form of colloidal manganese dioxide formed as a reaction product. Both the noncatalytic and the catalytic reaction pathways are first order in permanganate, the noncatalytic pathway is also first order in glycine, whereas the catalytic pathway has a kinetic order unity for the autocatalytic agent and a non-integral order (I .31) for glycine. Both reaction pathways are accelerated by an increase in the pH of the medium, whereas an increase in the buffer concentration at constant pH results in an increase in the rate of the noncatalytic pathway and a decrease in the rate of the catalytic one. Additions of potassium chloride to the solutions have no kinetic effect on the reaction. The apparent activation energies of the noncatalytic and catalytic reaction pathways are 64.5 and 62.0 kJ mol-I, respectively. On the other hand, manganese(II), thiosulfate, and hexacyanoferrate(I1) ions, as well as benzyltriethylammonium chloride and arabic gum, have all been found to increase the initial reaction rate. Mechanisms in concordance with the experimental findings are proposed. JOAQUIN F. PEREZ-BENITO, FERNANDO MATA-PEREZ et ENRIQUE BRILLAS. Can. J. Chem. 65, 2329 (1987. L'oxydation de la glycine par I'ion permanganate dans des tampons de phosphates aqueux est autocatalyste par la forme soluble du bioxyde de mangankse colloi'dal qui se forme comme produit de la reaction. Les voies riactionnelles tant de la reaction catalyske que de la rkaction qui n'est pas catalysCe sont toutes les deux du premier ordre en permanganate; par ailleurs, la reaction qui n'est pas catalysee est aussi du premier ordre en glycine alors que la reaction catalysie est du premier ordre pour l'agent autocatalytique et d'un ordre qui n'est pas entier (l,31) pour la glycine. Les deux voies reactionnelles sont accelCrCes par une augmentation du pH du milieu alors qu'une augmentation de la concentration du tampon i pH constant provoque une augmentation de la vitesse de la voie qui n'est pas catalyske et une diminution dans la vitesse de la rCaction catalyst. Des additions de chlorure de potassium aux solutions n'ont aucun effet cinitique sur la rCaction. Les energies d'activation apparentes pour les reactions catalysCe et non catalyske sont respectivement de 62,O et 64,5 kJ mol-'. Par ailleurs, on a trouvC que le mangankse(II), les ions thiosulfate et hexacyanoferrate(I1) ainsi que le chlorure de benzyltriCthylammonium et la gomme arabique augmentent tous la vitesse initiale de la reaction. On propose des mecanismes qui sont en accord avec les donnCes expirimentales.[Traduit par la revue]

“…Therevalue of the slope (0.24) is much lower than the kinetic order fore, Once manganese dioxide has been formed through the unity expected from eq. [27] for hydroxyl ion in the catalytic noncatal~ tic mechanism (eq. [ 17]), the catalytic mechanism mechanism.…”

Section: ] As: = As: -As'mentioning

confidence: 99%

“…Moreover, eq. [27] requires that k2 be directly taking place on the colloid surface can be determined by the propo~ional to [MeNH3+l, in open disagreement with the following equations: experimental situation (see Fig. 4 This equation represents an improvement with respect to eq.…”

Section: ] As: = As: -As'mentioning

confidence: 99%

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Kinetics and mechanisms of oxidation of methylamine by permanganate ion

Mata-Pérez¹,

Perez‐Benito²

1987

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. Can. J. Chem. 65, 2373 (1987). The oxidation of methylamine by permanganate ion in aqueous phosphate buffers is autocatalyzed by a soluble form of colloidal manganese dioxide temporarily stabilized in solution by adsorption of phosphate ions on its surface. The dependence of the rate constants of both the noncatalytic and catalytic mechanisms on the concentrations of both methylammonium and hydroxyl ions and on temperature has been determined. The activation parameters have been obtained. Mechanisms in agreement with the experimental data are proposed.FERNANDO MATA-PEREZ et JOAQUIN F. PEREZ-BENITO. Can. J. Chem. 65, 2373 (1987). L'oxydation de la mithylamine par l'ion permanganate, en solution dans des tampons de phosphates, est autocatalyste par une forme soluble du bioxyde de manganese colloidal qui est temporairement stabiliste en solution par adsorption des ions phosphates sur sa surface. On a dttermini les relations qui existent entre les constantes de vitesse, tant des micanismes catalysis que ceux des mtcanismes non-catalysts, et soit les concentrations tant des ions mithylammonium que des ions hydroxyles soit la temptrature. On a obtenu les paramttres d'activation. On propose des micanismes qui sont en accord avec les donntes expirimentales.[Traduit par la revue]