THE INDUCED DECOMPOSITION OF <i>tert</i>-BUTYL HYDROPEROXIDE

Hiatt, R.; Clipsham, John; Visser, Teunis

doi:10.1139/v64-408

Cited by 72 publications

(50 citation statements)

References 3 publications

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“…The known or estimated rate constants of reactions (4) and (5) imply that under the experimental conditions (i.e., [CyH] = 9.5 m and initial [ROOH] = 10 À2 m) the majority of the ROC radicals react rapidly (within % 3 ns) with ROOH to form ROOC radicals and ROH. This conclusion is in line with Visser and coworkers, who studied the consumption of tert-butylhydroperoxide by tert-butoxyl radicals generated by the thermal dissociation of di-tert-butylperoxyoxalate at 318 K. [30] We will return to the fate of the 5-10 % CyC radicals formed in reaction (4). Furthermore, b-scission of the tertbutoxyl radical can be neglected in the experimental T range.…”

supporting

confidence: 85%

Mechanism of the Catalytic Deperoxidation of tert‐Butylhydroperoxide with Cobalt(II) Acetylacetonate

Turrà

Neuenschwander

Baiker

et al. 2010

Chemistry A European J

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The Co(II)/Co(III)-induced decomposition of hydroperoxides is an important reaction in many industrial processes and is referred to as deperoxidation. In the first step of the so-called Haber-Weiss cycle, alkoxyl radicals and Co(III)-OH species are generated upon the reaction of the Co(II) ion with ROOH. The catalytic cycle is closed upon the regeneration of the Co(II) ion through the reaction of the Co(III)-OH species with a second ROOH molecule, thus producing one equivalent of the peroxyl radicals. Herein, the deperoxidation of tert-butylhydroperoxide by dissolved cobalt(II) acetylacetonate is studied by using UV/Vis spectroscopy in situ with a noninteracting solvent, namely, cyclohexane. Kinetic information extracted from experiments, together with quantum-chemical calculations, led to new mechanistic hypotheses. Even under anaerobic conditions, the Haber-Weiss cycle initiates a radical-chain destruction of ROOH propagated by both alkoxyl and peroxyl radicals. This chain mechanism rationalizes the high deperoxidation rates, which are directly proportional to the cobalt concentration up to approximately 75 μM at 333 K. However, at higher cobalt concentrations, a remarkable decrease of the rate is observed. The hypothesis put forward herein is that this remarkable autoinhibition effect could be explained by the hitherto overlooked chain termination of two Co(III)--OH species. The direct competition between the first-order Haber-Weiss initiation and the second-order termination can indeed explain this peculiar kinetic behavior of this homogeneous deperoxidation system.

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supporting

confidence: 85%

Mechanism of the Catalytic Deperoxidation of tert‐Butylhydroperoxide with Cobalt(II) Acetylacetonate

Turrà

Neuenschwander

Baiker

et al. 2010

Chemistry A European J

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“…Furthermore co-Clearly t-BuO,' is more selective than t-BuO. autoxidations always gave [2]/ [3] > [Y/[q probably which is consistent with the relative strengths ofthe because 3 is more susceptible to induced decompo-t-BuO-H and t-BuOO-H bonds (12,13). It is, sition than 6.…”

Section: 2-dimethylbutane-cyclohexanesupporting

confidence: 68%

“…We have, therefore, concluded that the reactivities of the secondary and primary hydrogens in and total product yields indicated that kinetic chain 2,2-dimethylbutane relative to cyclohexane, lengths were of the order of 2-15, i.e. they were kzn/klo, kb/klO, and k21klo are proportional to ([21 substantially longer than chain lengths for autoxi-+ [3])/( [6] + [7] Values of these relative rate constants at differ-drogens in n-butane are -45 times more reactive ent ratios of 2,2-dimethylbutane and cyclohexane than the primary hydrogens at 373 K while Van are given in Table 2 and absolute values of kz,, kB, Sickle, Mill, Mayo, and Richardson (9) have reand k,, per active H relative to absolute rate con-ported a relative selectivity of 38 for the primary stants for cyclohexane are given in Table 3.…”

Section: 2-dimethylbutane-cyclohexanementioning

confidence: 97%

Absolute rate constants for hydrocarbon autoxidation. 29. Rate constants for abstraction of primary aliphatic hydrogens from 2,2-dimethylbutane by the tert-butylperoxy radical

Howard¹,

Chenier²

1980

Can. J. Chem.

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Rate constants for abstraction of primary and secondary hydrogens from 2,2-dimethylbutane by the tert-butylperoxy radical at temperatures from 323 to 353 K have been determined from autoxidations and co-autoxidations in the presence of tert-butyl hydroperoxide. At 333 K the rate constant for abstraction of a secondary hydrogen is ~1.5 × 10−3 M−1 s−1 and the rate constants for abstraction of a primary hydrogen from the tert-butyl and methyl groups of 2,2-dimethylbutane are ~4 × 10−5 and ~6 × 10−5 M−5 s−1 respectively.

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“…This is comparable tions of 2-phenyl-I-propylperoxy radicals, indicat-with a.previous estimate of 6.3 (27) and with the ing that the involvement of these radicals in the analogous ratio for the tert-butylperoxy radical, for rate-controlling termination reactions is not impor-which k3b/k3, is estimated to be in the range 6-10 tant at ambient temperatures. Thus we are unable (27,33). The ratio k3b/k3a is thus comparable for the to concur with the conclusions reached by Bel-two alkylperoxy radicals within experimental yakov et al (14), on the basis of chemilumines-error, and differences in the ratio cannot account cence studies, that these radicals play an important for the factor of 5 difference between 2kt1 for the role during the autoxidation of cumene.…”

Section: Non-steady-state Studiesmentioning

confidence: 42%

Absolute rate constants for hydrocarbon autoxidation. 30. On the self-reaction of the α-cumylperoxy radical in solution

Howard¹,

Bennett²,

Brunton³

1981

Can. J. Chem.

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Can. J. Chem. 59.2253 (1981. Although it is generally accepted that the self-reaction of cumylperoxy radicals is a second-order process, recent reports have cast doubt on the overall validity of this assumption. Therefore we have reinvestigated some aspects of the self-reaction to clarify the kinetic and mechanistic features.Our product studies are entirely consistent with the accepted mechanism for the self-reaction of cumylperoxy radicals and no evidence was obtained for competing reactions. Results obtained with 360, labelled materials confirm the previous conclusion that reversible scission of cumylperoxy radicals to g h e oxygen and cumyl radicals does not compete significantly with the self-reaction 1 at ambient temperatures. Kinetic studies, under both steady-state and transient conditions, establish clearly that the self-reaction of cumylperoxy radicals is a second order process. A possible explanation is proposed to account for the previous observations which indicated that the self-reaction was a first order process. Further, we show that the changes observed in the esr spectrum of the cumylperoxy radicals, which were attributed to the formation of a complex with cumyl hydroperoxide, are caused by changes in the 1 viscosity of the solution. De recentes publications ont mis en doute la validite de I'hypothbse generalement acceptee a I'effet que I'autoreaction des radicaux cumylperoxy est une reaction d'ordre 2. Nous avons donc reexamine quelques aspects de cette reaction afin d'en clarifier les caracteristiques cinetiques et mecanistiques.Nos etudes sont entitrement en accord avec le mecanisme accepte pour I'auto-reaction des radicaux cumylperoxy et nous n'avons pas trouve de donnees permettant de croire qu'il existe des reactions en competition. Les resultats obtenus avec des produits marques au 360, confirment ce qui a ete trouve anterieurement a savoir que, a la temperature ambiante la scission reversible des radicaux cumylperoxy qui donne de I'oxygene et des racidaux cumyles n'entre pas en competition de f a~o n significative avec I'auto-reaction. Des etudes cinetiques tant dans des conditions d'etat stationnaire que transitoire etablissent clairement que I'auto-reaction des radicaux cumylperoxy est d'ordre 2. On propose une explication possible des observations anterieures qui indiquent une reaction du premier ordre. De plus, nous montrons que les variations observees dans les spectres rpe des radicaux cumylperoxy, qui ont ete attribuees a la formation d'un complexe avec I'hydroperoxyde de cumyle, sont provoquees par des variations dans la viscosite de la solution.[Traduit par le journal]

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THE INDUCED DECOMPOSITION OF tert-BUTYL HYDROPEROXIDE

Cited by 72 publications

References 3 publications

Mechanism of the Catalytic Deperoxidation of tert‐Butylhydroperoxide with Cobalt(II) Acetylacetonate

Mechanism of the Catalytic Deperoxidation of tert‐Butylhydroperoxide with Cobalt(II) Acetylacetonate

Absolute rate constants for hydrocarbon autoxidation. 29. Rate constants for abstraction of primary aliphatic hydrogens from 2,2-dimethylbutane by the tert-butylperoxy radical

Absolute rate constants for hydrocarbon autoxidation. 30. On the self-reaction of the α-cumylperoxy radical in solution

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