The Oxidation of Free Methyl Radicals

Raley, John H.; Porter, L. M.; Rust, Frederick F.; Vaughan, Worth E.

doi:10.1021/ja01145a005

Cited by 43 publications

(22 citation statements)

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“…The agreement between the rate constant for DTBP calculated froill the rate of acetone formation in the presence of oxygen (Table I) and the lcnown rate constant a t the same temperature is strong evidence that the rate of forlnation of methyl radicals by [I] and [2] is unaffected by the presence of oxygen. Raley et al came to the same coilclusioi~ (2).…”

Section: Discussionmentioning

confidence: 57%

“…Presun~ably the fate of hydroxyl radicals is reaction with D T B P t o form water. T h e radical CI-12(CI-I3)2COOC(CI-I3)3 formed by that abstraction might decoinpose t o isobutylene oxide and a t-butoxy radical so that, taken with [2], [3], and [5], the elements of a chain are present. It was pointed out above that the presence of a short chain in this region of conversion is not incompatible with the acetone yield observed.…”

Section: Discussionmentioning

confidence: 99%

“…Raley et al (2) used this method to study the oxidation of methyl radicals but their reactions were carried t o large conversions. T h e experin~ents reported by Bose (3) were also done a t high conversion.…”

Section: Introductionmentioning

confidence: 99%

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THE OXIDATION OF DI-tertiary-BUTYL PEROXIDE

Blake¹,

Kutschke²

1961

Can. J. Chem.

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The oxidation of di-t-butyl peroxide has been investigated in a static system a t low conversion a t 124' C with sufficient oxygen present t o suppress completely the formation of methane and ethane. T h e decolllposition of the t-butoxy radical is unaffected by the presence of oxygen. A major product of the oxidation is formaldehyde whose yield rapidly approaches a stationary value. I t is postulated t h a t the major source of formaldehyde is the decomposition of methyl peroxy radicals, which may also abstract hydrogen from formaldehyde to form methyl hydroperoxide, and that this competition leads to the stationary concentration of formaldehyde actually observed. Methyl hydroperoxide was demonstrated t o be unstable in the system and the predominant decomposition product: was methanol, a compound also found in high yields in the oxidation. Experiments with added formaldehyde-C13 showed that formaldehyde can be converted to carbon n~oiloxide in the system and indicated that formaldehyde was a likely precursor to the carbon monoxide found in the oxidation. INTRODUCTIONT h e pyrolysis of di-t-butyl peroxide (DTBP) provides a particularly coilveilient source of methyl radicals because of the high activation energy (I) required for the abstraction of hydrogen from that compound. Raley et al. (2) used this method to study the oxidation of methyl radicals but their reactions were carried t o large conversions. T h e experin~ents reported by Bose (3) were also done a t high conversion. The present study was undertaken to extend this work to !ower (<5%) coi~versioi~s and to investigate the effect of conversion on the rates of production of the inajor products. The role of formaldehyde as a hydrogen donor in the photooxidation of azomethaile has been iilvestigated previously in this laboratory (4, 5, 6). Experiments are reported in which formaldehyde-C13 was added to the reactailts in the present systein to investigate this point further. E X P E R I M E N T A LMost of the apparatus was the same as that described in a previous communication (1). A reactioil was started by expanding a mixture of oxygen and D T B P from a preheater held a t 80" C, where pressures could be measured on a quartz spiral gauge, to the Pyrex reaction vessel (volume, 550 ml) the temperature of which could be held to within 0.1" C.Analyses were made for carbon monoxide, acetone, methanol, and formaldehyde; the yields of methane and ethane were vanishingly small. Formaldehyde, oxygen, and carbon monoxide were separated from the liquid products (acetone, methanol, and unreacted DTBP) by passage through a trap held a t -130" C. Formaldehyde was condensed in a second trap a t -196" C and the permanent gases were transferred to a tube containing a mixture of copper and cupric oxide where the carbon monoxide was oxidized a t 270" C. T h e liquid products were analyzed by gas chromatography on a 10-ft column containing 25% dinonyl phthalate and 5% glycerol on Fisher Columpalc (30-60 mesh). With a hydrogen flow rate of 45 ml/minute a t 29" C appe...

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Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

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THE OXIDATION OF DI-tertiary-BUTYL PEROXIDE

Blake¹,

Kutschke²

1961

Can. J. Chem.

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“…I t is difficult to identify this inhibitor specifically. Because of the low value which has been quoted (8) for the activation energy of the reaction of inethyl radicals with formaldehyde, it was thought possible that radicals in the system could react with formaldehyde thus consuming formaldehyde and possibly acting as a source of the carbon monoxide found, as has been suggested before (6,9). Such a suggestion would, indeed, explain the results, in a qualitative way a t least.…”

Section: Discussionmentioning

confidence: 61%

The Photooxidation of Azomethane. Ii

Wenger¹,

Kutschke²

1959

Can. J. Chem.

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In a further investigation of the photooxidation of azomethane it was found t h a t the yields of all products depend on the fractional conversioll in a manner which suggests that some inhibitor is produced. Products from experiments a t lower pressures of azolnethane are obtained in yields appropriate to the higher conversions. Only very slnall changes in yields are observed for relatively large variations in light intensity. T h e implications of these facts t o the mechanism of the photooxidation are discussed.In an earlier i~~vestigation of the photooxidation of azomethane ( I ) it was postulated that formaldehyde should be a major product of the reaction. I t proved impossible to detect this product, however, presumably because of the well-known tendency of the material to polymerize a t temperatures below 100" C (2).Preliminary work, iildicatiilg that formaldehyde was indeed an important product, was done as follows. The mixture of reaction products, unreactecl azomethane, and oxygen was condensed a t -196" C in a small side arm attached to a grease-free reaction system. After the side arm was allowed to warm to room temperature, the vapor phase was removed by pumping for several minutes and the side arm sealed off. The invisible residue in the side arm was dissolved in dilute H2S04 and the chromotropic acid test (3) applied to the resulti~lg solution. Positive identification was achieved, which was not due to hydrolysis of residual azomethane as shown by the absence of a test on the unphotolyzed mixture.A reaction system was constructecl based 011 this technique for the ailalysis of formaldehyde. E X P E R I M E N T A LThe reaction system consisted of a fused quartz reaction cell (4.8 cin i.d., 10 cm long, -180 cm3 volume), a glass-enclosed, magnetically driven stirrer, a U-tube through which the cell contents were circulatecl, and conilectiilg tubing. Reactants were introduced from storage and manometers through a stainless steel diaphragm valve (Hoke, No. 413) and led to the analytical system through a similar valve. The entire system, including the valves but excluding the U-tube, was housed in a thermostatted air oven. Gradients and fluctuations in the region of the cell were less than 1" C. Other parts of the oven had larger gradients so that temperature differences of as much as 5" C existed between the cell and other units in the oven. The U-tube, which extended through the walls of the oven, could be kept a t oven temperature with heating tape or cooled to any temperature desired.Gases were led from the reaction system through heated tubing to a removable U-tube (Dow Corning Silicone greased joints), and thence to a Hg cutoff leading to LeRoy stills (4) and a grease-free gas burette. 'Manz~script received M a y 8, 1969.

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“…:itrated in a number of hydrogen-donating solvents (96). The bimolecular oxygen forming reaction 24 has been inferred by the authors from their work with methyl radicals (93). However, the same conclusion could have been drawn from the earlier work by Milas & Surgenor (97), who decomposed tert-butyl hydroperoxide to obtain an almost quantitative yield of O2 and tert-butyl alcohol, presumably by way of reaction 24 and the reverse of 20.…”

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confidence: 69%

Reaction Kinetics

Powell¹

1952

Annu. Rev. Phys. Chem.

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Since scientific papers which could be catalogued as reaction kinetics are currently being published at a rate of more than a thousand per year, a simple bibliography of one year's pUblications would fill the space allotted this review. Fortunately for the reviewer, many papers fall into special fields such as photochemistry, polymerization, contact catalysis, isotopic studies, or biochemical kinetics, which will be reviewed separately in the present volume or succeeding volumes of the Annual Review of Physical Chemistry.

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The Oxidation of Free Methyl Radicals

Cited by 43 publications

References 0 publications

THE OXIDATION OF DI-tertiary-BUTYL PEROXIDE

THE OXIDATION OF DI-tertiary-BUTYL PEROXIDE

The Photooxidation of Azomethane. Ii

Reaction Kinetics

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