The equilibrium constant and rate constant for allyl radical recombination in the gas phase

Rossi, Michel J.; King, Keith D.; Golden, D. M.

doi:10.1021/ja00499a029

Cited by 80 publications

(38 citation statements)

References 5 publications

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“…The poorest results concern the production of CH 4 , C 2 H 4 , and CO, as the simulated profiles are systematically under the experimental ones. The same difficulty was observed for CH 4 and C 2 H 4 in the absence of oxygen [1] and it is due to a deficit of dienes over alkanes which is not simulated, of course, by the model. The present scheme has been oversimplified since C 9 radicals were not considered.…”

Section: Discussionmentioning

confidence: 53%

“…As it has recently been shown [1], the products of the thermal reaction of propene in the absence of oxygen are numerous: H 2 , CH 4 , C 2 H 4 , C 2 H 6 , C 3 H 4 (allene), C 3 H 8 , 1,3-C 4 H 6 , 1-C 4 H 8 , 2-C 4 H 8 (cis and trans), i-C 4 H 8 , 4-methylpent-1-ene (M4P1), 3-methyl and 4-methylcyclopentene a mixture of 1,4-and (c-C H ), 6 10 1,5-hexadiene methylcyclopentane (or di-(d-C H ), 6 10 methylcyclobutane since chromatographic data are not sure)…”

Section: Reaction Productsmentioning

confidence: 99%

“…31 10 min 4 ). The propagation steps of the radical part CH ϭ 0.02 4 of the reaction which clearly appear to be rate-determining for most of products are practically those in the absence of oxygen: (1), (Ϫ 1), (3), (Ϫ 3), (4), (13), (15) - (19), (29) …”

Section: Modelingmentioning

confidence: 99%

“…have been determined [4,5]. But, the oxidation chemistry of allyl radicals remains a matter of controversy.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

Barbè¹,

Baronnet²,

Martin³

et al. 1998

Int. J. Chem. Kinet.

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The thermal reaction of propene was examined around in the presence of 800 K less than 20% oxygen. At initial time, the production of H 2 , CH 4 , C 2 H 4 , C 2 H 6 , allene, C 3 H 8 , 1,3-butadiene, butenes, 3-and 4-methylcyclopentene, a mixture of 1,4-and 1,5-hexadienes, methylcyclopentane (or dimethylcyclobutane), 4-methylpent-1-ene, and hex-1-ene, was observed along with hydrogen peroxide, CO, and small quantities of ethanal and CO 2 . Oxygen increases the initial production of hydrogen and of most hydrocarbons and, particularly, that of C 6 dienes and of cyclenes. However, the production of allene, methylcyclopentane (or dimethylcyclobutane), and 4-methylpent-1-ene is practically not affected. A kinetic study confirms the mechanism proposed for the thermal reaction of propene. Formation of allene, thus, involves a four-center-unimolecular dehydrogenation of propene, that of 4-methylpent-1-ene is explained by an ene bimolecular reaction while methylcyclopentane (or dimethylcyclobutane) probably arises from a bimolecular process involving a biradical intermediate. Other products arise from a conventional chain radical mechanism.A kinetic scheme is proposed in which chains are primarily initiated by the bimolecular step:which competes with the second-order initiation of propene pyrolysis. Since allene production is not affected by oxygen, it is concluded that allyl radicals are not dehydrogenated by oxygen; but they oxidize in a branching step involving allylperoxyl radicals; r. radicals other than methyl, and allyl are dehydrogenated according to the conventional process:r· ϩ O !: unsaturated ϩ HO · 2 2

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Section: Discussionmentioning

confidence: 53%

Section: Reaction Productsmentioning

confidence: 99%

Section: Modelingmentioning

confidence: 99%

“…have been determined [4,5]. But, the oxidation chemistry of allyl radicals remains a matter of controversy.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

Barbè¹,

Baronnet²,

Martin³

et al. 1998

Int. J. Chem. Kinet.

View full text Add to dashboard Cite

show abstract

“…A choice of model for simple bond fission is available: the commonly used vibrational model [ 131 or the recently developed hindered rotational Gorin model [14]. Recently it has become apparent that the vibrational model is inadequate except perhaps for those systems showing extensive electronic rearrangement in the incipient radical(s) [15]. In view of the known resonance stabilization of propargyl radicals we have performed RRKM calculations using both types of transition-state models.…”

Section: Rrkm Calculationsmentioning

confidence: 99%

Very low‐pressure pyrolysis (VLPP) of pentynes. II. 4‐methylpent‐2‐yne and 4,4‐dimethylpent‐2‐yne. Heats of formation and resonance stabilization energies of methyl‐substituted propargyl radicals

King

Nguyen

1981

Int J of Chemical Kinetics

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Studies of the unimolecular decomposition o f 4-methylpent-2-yne (M2P) and 4,4-dimethylpent-2-yne (DMZP) have been carried out over the temperature range of 903-1246 K using the technique of very-low pressure pyrolysis (VLPP). T h e primary reaction for both compounds is fission of the C-C bond adjacent to the acetylenic group producing the resonance-stabilized methyl-substituted propargyl radicals, CH:3C=CCH(CH3) from M2P and CH&=Cc(CH& from DM2P. RRKM calculations were performed in conjunction with both vibrational and hindered rotational models for the transition state. Employing the usual assumption of unit efficiency for gas-wall collisions, the results show that only the rotational model with a temperature-dependent hindrance parameter gives a proper fit to the V L P P data over the entire experimental temperature range. T h e high-pressure Arrhenius parameters a t 1100 K are given by the rate expressions log k 2 (sec-l) = (16. 2

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The Influence of Unimolecular Fall‐off Behaviour on Pyrolysis Systems. A Case Study

Olzmann¹,

Scherzer²,

Schwede³

1991

Ber Bunsenges Phys Chem

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The influence of unimolecular fall‐off effects on the kinetic modelling of larger pyrolysis systems is estimated theoretically for the case of propane decomposition at nearly industrial conditions (1100 K, 0.1 MPa). The ordinary differential equation system based on a mechanism of 34 elementary reactions and 20 chemical species is integrated by means of a Gear algorithm two times, on the one hand with the thermal high‐pressure rate constants and on the other hand with constants corrected for the fall‐off effects in the case of unimolecular as well as in the case of bimolecular association reactions. RRKM theory, combined with an empirical treatment of weak‐collision effects, provides ratios of k/k∞ between 0.2 and 0.9. It turns out that corrections in this order of magnitude have only little influence on the concentrations of stable products, whereas radical species show, at least partly, a higher sensitivity. This results in larger deviations of the concentrations of compounds formed by radical recombination that, nevertheless, contribute to the overall products only to a small extent.

show abstract

The equilibrium constant and rate constant for allyl radical recombination in the gas phase

Cited by 80 publications

References 5 publications

Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

Very low‐pressure pyrolysis (VLPP) of pentynes. II. 4‐methylpent‐2‐yne and 4,4‐dimethylpent‐2‐yne. Heats of formation and resonance stabilization energies of methyl‐substituted propargyl radicals

The Influence of Unimolecular Fall‐off Behaviour on Pyrolysis Systems. A Case Study

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