Mechanism of the thermal decomposition of substituted tetraoxanes in benzene solution: effect of substituents on the activation parameters of the unimolecular reactions

Cafferata, Lázaro F. R.; Eyler, Gladys N.; Svartman, E. L.; Cañizo, Adriana I.; Borkowski, Eduardo Jorge

doi:10.1021/jo00290a045

Cited by 37 publications

(52 citation statements)

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“…A veces la correlación entre ambos parámetros se aproxima a una relación lineal característica para esa serie de reacciones en particular 24 . Existen en la literatura [4][5][6]8,9,25 antecedentes que muestran este efecto para otros peróxidos cíclicos.…”

Section: Resultados Y Discusionunclassified

“…De acuerdo a los resultados obtenidos en estudios anteriores la constante de velocidad correspondiente a la descomposición térmica de DPP no es sensiblemente afectada cuando la reacción se lleva a cabo en benceno 4 , acetonitrilo 5 , ácido acético 5 , n-octano 5 o tolueno 6 . Por ello, resulta de interés encontrar algún solvente donde se aumente la velocidad de la reacción de descomposición del DPP.…”

Section: Introduccionunclassified

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Descomposicion termica del diperoxido de pinacolona (3,6-diterbutil-3,6-dimetil-1,2,4,5-tetraoxaciclohexano) en solución de 2-metoxietanol

2002

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Recebido em 5/1/01; aceito em 14/11/01 THERMAL DECOMPOSITION OF PINACOLONE DIPEROXIDE (3,6-ditertbutyl-3,6-dimethyl-1,2,4,5-tetraoxacyclohexane) IN 2-METHOXYETHANOL SOLUTION. The thermal decomposition reaction of pinacolone diperoxide (DPP; 0.02 mol kg -1 ) in 2-methoxyethanol solution studied in the temperature range of 110.0-150.0 °C, follows a first-order kinetic law up to at least 50% DPP conversion. The organic products observed were pinacolone, methane and tert-butane. A stepwise mechanism of decomposition was proposed where the first step is the homolytic unimolecular rupture of the O-O bond. The activation enthalpy and activation entropy for DPP in 2-methoxyethanol were calculated (DH # = 43.8 ± 1.0 kcal mol -1 and DS # = 31.9 ± 2.6 cal mol -1 K -1 ) and compared with those obtained in other solvents to evaluate the solvent effect.Keywords: cyclic peroxide; kinetic; solvent effect. INTRODUCCIONLos peróxidos orgánicos son compuestos que tienen gran importancia en numerosas reacciones de combustión e importantes aplicaciones industriales tales como iniciadores de polimerización, agentes de entrecruzamiento, blanqueadores, desinfectantes, etc.Los estudios cinéticos y mecanísticos correspondientes a la termólisis en solución de peróxidos orgánicos cíclicos y todas las comparaciones entre ellos que de allí surgen, han sido el objetivo inicial de este grupo de investigación. Sin embargo, en los últimos años ha resultado de gran interés la aplicación de este tipo de compuestos como iniciadores polifuncionales en los procesos de polimerización radicálica de estireno. Si bien el diperóxido de pinacolona (3,6-diterbutil-3,6-dimetil-1,2,4,5-tetraoxaciclohexano, DPP; Figura 1) fue utilizado hace varias décadas como iniciador en la obtención de poliestireno 1 , actualmente, a través de la introducción de algunas modificaciones en las condiciones de trabajo, se ha logrado su utilización a temperaturas relativamente altas y con mayores conversiones del monómero (ca. 99 %) 2 . Por lo tanto, el estudio del comportamiento de estos peróxidos en solución es complementario de los estudios relacionados con su aplicación en procesos industriales.Las técnicas de polimerización que se están desarrollando contemplan el agregado del peróxido cíclico polifuncional en estado sólido 2 o en solución 3 , dando en cada caso diferentes resultados. De todos los peróxidos orgánicos cíclicos estudiados hasta el momento, el DPP y el triperóxido cíclico de dietilcetona (TPDEC) son los que han manifestado el mejor comportamiento como iniciadores polifuncionales. Sin embargo, el efecto de solvente que presentan algunos peróxidos orgánicos en su descomposición térmica no siempre se transmite en el mismo sentido en relación a su función como iniciador cuando se lo agrega en solución, como se ha evidenciado para el TPDEC 3 .De acuerdo a los resultados obtenidos en estudios anteriores la constante de velocidad correspondiente a la descomposición térmica de DPP no es sensiblemente afectada cuando la reacción se lleva a cabo en benceno 4 , acetonitri...

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Section: Resultados Y Discusionunclassified

Section: Introduccionunclassified

Descomposicion termica del diperoxido de pinacolona (3,6-diterbutil-3,6-dimetil-1,2,4,5-tetraoxaciclohexano) en solución de 2-metoxietanol

2002

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“…cyclic diperoxide derived from 3, 3-dimethyl-2-butanone (pinacolone) decomposes in different solvents at higher rates than ACDP. 2,8,11 The presence of deuterium in dACDP and the kinetic behavior shown allow postulating a KIE. The relation between kinetic constants that are greater than 1 (k H /k D > 1) is referred to as normal KIE, while those that are less than one is referred to as inverse KIE (k H /k D <1).…”

Section: Kinetic Analysismentioning

confidence: 99%

“…In aromatic or aliphatic solvents with low polarity (toluene, benzene and n-octane), the rate constant values are smaller 2,8,9 . The trend demonstrates that an increase in the solvent polarity is accompanied by an increase in the reaction rate as a consequence of a reaction mechanism involving a more dipolar-activated complex than the diperoxide initial molecule, which could be stabilized by polar solvents.…”

Section: Kinetic Analysismentioning

confidence: 99%

“…2,7 In previous works, it was demonstrated that an important substituent effect is operative on kinetic and activation parameters of the thermal decomposition reaction of substituted tetraoxacyclohexanes derived from acetone, pinacolone, 4-heptanone, benzophenone, dibenzylketone, cyclohexanone or acetophenone in different organic solvents. 3,[8][9][10][11] It has been widely published that the rate-determining step of the thermal decomposition reaction of the cyclic peroxides is the biradical intermediate formation (Eq. 1).…”

Section: Introductionmentioning

confidence: 99%

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Thermal decomposition reaction in ethanol solution of deuterated acetone cyclic diperoxide and acetone diperoxide. Secondary inverse isotopic effect

Nesprías¹,

Eyler²,

Cañizo³

et al. 2017

Quim. Nova

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The characterization by mass spectrometry and the kinetic study of the thermal decomposition reaction of deuterated acetone diperoxide (dACDP) was studied in ethanol in the 140-165 °C temperature range. The comparison with the non deuterated species (ACDP) was also made. The kinetic behavior observed for both compounds follows a pseudo first order kinetic law up to at least 86 % peroxide conversions. It could be observed that under the established experimental conditions, the dACDP decomposes ca. 1.2 times faster than the ACDP. The activation parameters were calculated for both peroxides and allowed to postulate a single process initial step, the unimolecular thermal decomposition through the O-O bond cleavage to form an intermediate biradical. The products of the acetone derived peroxides thermal decomposition support a radical-based decomposition mechanism. The changes in kinetic parameters between dACDP and ACDP were justified attending to differences in ring substituents sizes. A secondary inverse kinetic isotope effect is observed (k H /k D <1).

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Kinetics and mechanism of thermolysis of fluorine substituted 1,2,4-trioxanes in methanol solution

Cafferata

Jefford

Rimada

2000

Int. J. Chem. Kinet.

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The kinetics of the thermal decomposition reactions of two fluorine substituted 1,2,4‐trioxanes: cis‐6‐(4‐fluorophenyl)‐5,6‐{2‐(4‐fluorophenyl)‐propyliden}‐3,3‐tetramethylene‐1,2,4‐trioxacyclohexane (I) and cis‐6‐(4‐fluorophenyl)‐5,6‐{2‐(4‐fluorophenyl)}‐3‐hydroxypropiliden‐3,3‐tetramethylene‐1,2,4‐trioxacyclohexane (II), were investigated in methanol solutions in the temperatures and concentrations ranges of 393.2–428.2 K and (1.05–247) × 10−5 M, respectively. First‐order rate constant values were obtained up to 84–98% conversions of those cyclic peroxides. The corresponding values of the activation parameters for the initial unimolecular homolysis of their molecules, together with the products analyses of the reaction, support stepwise mechanisms of thermolysis. However, similar reaction pathways can be postulated for those reactions but with different ground or transition states for the corresponding peroxidic bond ruptures. Participation of the methanol solvent molecules in secondary free radical reactions of their mechanism is demonstrated. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 523–528, 2000

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Mechanism of the thermal decomposition of substituted tetraoxanes in benzene solution: effect of substituents on the activation parameters of the unimolecular reactions

Cited by 37 publications

References 0 publications

Descomposicion termica del diperoxido de pinacolona (3,6-diterbutil-3,6-dimetil-1,2,4,5-tetraoxaciclohexano) en solución de 2-metoxietanol

Descomposicion termica del diperoxido de pinacolona (3,6-diterbutil-3,6-dimetil-1,2,4,5-tetraoxaciclohexano) en solución de 2-metoxietanol

Thermal decomposition reaction in ethanol solution of deuterated acetone cyclic diperoxide and acetone diperoxide. Secondary inverse isotopic effect

Kinetics and mechanism of thermolysis of fluorine substituted 1,2,4-trioxanes in methanol solution

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