Decompositions of Di-t-Alkyl Peroxides. I. Kinetics

Raley, John H.; Rust, Frederick F.; Vaughan, William E.

doi:10.1021/ja01181a027

Cited by 128 publications

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“…I . This leads to a rate constant, kl = 2.5XlOl6 exp(-38,70O/RT) sec-', in excellent agreement with those previously determined (3,4,5,6,7,8 …”

Section: Peroxide Alonesupporting

confidence: 89%

The Reaction of Methyl Radicals With Formaldehyde

Blake¹,

Kutschke²

1959

Can. J. Chem.

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The pyrolysis of di-t-butyl peroxide has been reinvestigated and used as a source of methyl radicals to study the abstraction reaction between methyl radicals and formaldehyde. At low [IHCIlO]/[peroxidc] ratios the system was simple enough for kinetic analysis, and a value of 6.6 Iccal/mole was obtained for the activation energy. At higher [HCHOl/[peroxide] ratios the system became very complicated, possibly due to the increased inlportance of addition reactions. INTRODUCTIONThe reaction between methyl radicals and formaldehyde has been previously studied by Kodama and Taltezalti (1) and by Toby and ICutschke (2), who used the photolysis of azomethane as a source of inethyl radicals. They obtained values of 5.6 and 6.2 kcal/ mole, respectively, for the activation energy of the process. I t seemed desirable to reinvestigate the reaction using the pyrolysis of di-t-butyl peroxide as a source of methyl radicals. This source possesses the advantage that there is little abstraction reaction between methyl radicals and the n~olecule which produces the radicals.Methyl radicals were produced by the pyrolysis of di-t-butyl peroxide in a Pyrex glass reaction vessel (volume = 550 cm3) the temperature of which was controlled to within 0.1" C. T o start the reaction the reactants were expanded into the cell from a preheater maintained a t 80" C, a t which temperature no measurable decomposition of the peroxide took place in a period of 30 minutes. The reaction was stopped by expansion into a liquid-nitrogen-cooled trap. The products were analyzed by conventional methods. CHI and CO were separated from the remaining products a t -210" C, and the CO measured as C 0 2 after oxidation in a copper oxide furnace a t 260' C. Methane was removed directly from the furnace and measured. Ethane was distilled from Ward stills a t -180" C. The purity of each fraction was checked lnass spectrolnetrically in some experiments. The remailling lnixture of liquid products and unreacted starting materials was removed for further analysis. Liquid product analyses for acetone, t-butanol, and acetaldehyde mere carried out gas chro~natographically on a 10-ft column consisting of 30% nonyl-phthalate on firebrick, with a small proportion of polyethylene glycol added to the phthalate to cut down tailing of the peaks. No substances were detected other than the residual reactants and those products for which analyses are given.Di-t-butyl peroxide, fro111 the Novadel-Agene Corporation, contained traces of acetone and methanol and approximately 1/2% t-butanol. The first two were entirely removed by chromatographic purification; the t-butanol content was reduced to < 0.1% by this treatment. Isobutane mas Phillips Research Grade. Formaldehyde was prepared by heating a-polyoxy~nethyle~le followed by distillation in vacz~o. All these materials were thoroughly outgassed before use.lA!fanz~script recei-ded M a y 14, 1969.

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“…I . This leads to a rate constant, kl = 2.5XlOl6 exp(-38,70O/RT) sec-', in excellent agreement with those previously determined (3,4,5,6,7,8 …”

Section: Peroxide Alonesupporting

confidence: 89%

The Reaction of Methyl Radicals With Formaldehyde

Blake¹,

Kutschke²

1959

Can. J. Chem.

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“…The kinetics of R818 were determined by Raley et al 8 60 years ago and the process has been extensively studied since. The available rate data 9 are in good agreement.…”

Section: Experimental Methodsmentioning

confidence: 99%

Evaluated Kinetics of the Reactions of H and CH₃ with n-Alkanes: Experiments with n-Butane and a Combustion Model Reaction Network Analysis

2015

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Presented is a combined experimental and modeling study of the kinetics of the reactions of H and CH3 with n-butane, a representative aliphatic fuel. Abstraction of H from n-alkane fuels creates alkyl radicals that rapidly decompose at high temperatures to alkenes and daughter radicals. In combustion and pyrolysis, the branching ratio for attack on primary and secondary hydrogens is a key determinant of the initial olefin and radical pool, and results propagate through the chemistry of ignition, combustion, and byproduct formation. Experiments to determine relative and absolute rate constants for attack of H and CH3 have been carried out in a shock tube between 859 and 1136 K for methyl radicals and 890 to 1146 K for H atoms. Pressures ranged from 140 to 410 kPa. Appropriate precursors are used to thermally generate H and CH3 in separate experiments under dilute and well-defined conditions. A mathematical design algorithm has been applied to select the optimum experimental conditions. In conjunction with postshock product analyses, a network analysis based on the detailed chemical kinetic combustion model JetSurf 2 has been applied. Polynomial chaos expansion techniques and Monte Carlo methods are used to analyze the data and assess uncertainties. The present results provide the first experimental measurements of the branching ratios for attack of H and CH3 on primary and secondary hydrogens at temperatures near 1000 K. Results from the literature are reviewed and combined with the present data to generate evaluated rate expressions for attack on n-butane covering 300 to 2000 K for H atoms and 400 to 2000 K for methyl radicals. Values for generic n-alkanes and related hydrocarbons are also recommended. The present experiments and network analysis further demonstrate that the C-H bond scission channels in butyl radicals are an order of magnitude less important than currently indicated by JetSurf 2. Updated rate expressions for butyl radical fragmentation reactions are provided.

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“…The extended Huckel molecular orbital theory15) was adopted for the investigation of these four items. 2 …”

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confidence: 99%

Bond Nature of Peroxides and Related Compounds

Ohkubo

Kitagawa

Sakamoto

1971

Bull. Japan Petrol. Inst.

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Summary:Extended Huckel molecular orbital calculations were performed on various peroxides (hydroperoxides, peracids, and peresters), nitrites, nitrates, esters, ethers, and alcohols with particular reference to the bond nature of their O-O, O-N, C-O, and O-H linkages. We made several findings. Firstly, the order of the bond strengths of the above linkages in the compounds considered was: alcohol>ester>ether>>nitrate>nitrite>>hydroperoxide>peroxide>perester> peracid. Secondly, peroxide families or nitrite and nitrate families were characterized by the lowest unoccupied (or the LU+1), antibonding O-O or O-N linkages. Thirdly, a parallel between the overlap population of the above linkages (O-O or O-N) and their bond dissociation energies could be recognized, with certain irregularities. Fourthly, the monomer structures of alkyl hydroperoxides were more energetically stable and reactive to nucleophiles than dimer ones. Finally, the characteristic bond nature of the above linkages was discussed in connection with the wave function contours.

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Decompositions of Di-t-Alkyl Peroxides. I. Kinetics

Cited by 128 publications

References 0 publications

The Reaction of Methyl Radicals With Formaldehyde

The Reaction of Methyl Radicals With Formaldehyde

Evaluated Kinetics of the Reactions of H and CH₃ with n-Alkanes: Experiments with n-Butane and a Combustion Model Reaction Network Analysis

Bond Nature of Peroxides and Related Compounds

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Decompositions of Di-t-Alkyl Peroxides. I. Kinetics

Cited by 128 publications

References 0 publications

The Reaction of Methyl Radicals With Formaldehyde

The Reaction of Methyl Radicals With Formaldehyde

Evaluated Kinetics of the Reactions of H and CH3 with n-Alkanes: Experiments with n-Butane and a Combustion Model Reaction Network Analysis

Bond Nature of Peroxides and Related Compounds

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Evaluated Kinetics of the Reactions of H and CH₃ with n-Alkanes: Experiments with n-Butane and a Combustion Model Reaction Network Analysis