Zu möglichen Umlagerangen zwischen isomeren C<sub>3</sub>H<sub>5</sub>-Radikalen

Ondruschka, Bernd; Ziegler, U.; Zimmermann, G.

doi:10.1515/zpch-1986-267144

Cited by 11 publications

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“… Reactions 8‘ and 8‘ ‘ are dissociative reactions following isomerization to the 2-propenyl radical, which branches to H + propyne as the major product channel whereas the allyl radical gives only allene + H directly. Therefore, detecting branching to the propyne + H channel indicates that the allyl → 2-propenyl radical isomerization is competitive with the direct C−H bond fission from the allyl radical to produce allene + H. The experimentally determined allyl → 2-propenyl radical isomerization barrier is 15 kcal/mol lower than the calculated values, so these experiments can definitively resolve which is correct.…”

Section: Introductionmentioning

confidence: 79%

“…The other important result from this work is the clear evidence that the previous experimental determination of the barrier height for allyl → 2-propenyl isomerization is too low. Whereas the two recent ab initio studies predict the barrier to be near 64 kcal/mol, , the 1986 experimental study determined the barrier to be 48.6 kcal/mol . RRKM calculations were performed 40 using the barrier heights and frequencies of Davis et al as well as the 48.6-kcal/mol barrier height to determine the expected major pathways at the energies available here.…”

Section: Discussionmentioning

confidence: 99%

“…Particularly at near-threshold internal energies, where the 2-propenyl radical has a fast H + propyne dissociation channel, the faster isomerization to 2-propenyl calculated by assuming that the lower barrier is correct would give a dominant branching to the H + propyne product, in contradiction to our experimental results. b From ref . c From ref .…”

Section: Discussionmentioning

confidence: 99%

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Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

et al. 2002

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In the work presented here, we used photofragment translational spectroscopy and H atom Rydberg timeof-flight (HRTOF) spectroscopy to study the primary photofragmentation channels of allyl iodide excited at 193 nm and the ensuing dissociation of the nascent allyl radicals as a function of their internal energy. Two C-I bond fission channels were found to produce the allyl radical, one channel forming I( 2 P 3/2 ) and the other forming I( 2 P 1/2 ). The nascent allyl radicals are dispersed as a function of the translational energy imparted from the photolysis and therefore by their internal energy. Although all of the I( 2 P 3/2 ) and a portion of the I( 2 P 1/2 ) channel allyl radical products have enough internal energy to overcome the 60 kcal/mol barrier to form allene + H, the data showed that a substantial fraction of the allyl radicals from the I( 2 P 1/2 ) channel that formed with internal energies as high as 15 kcal/mol above the 60 kcal/mol barrier were stable to H atom loss. The stability is due to centrifugal effects caused by significant rotational energy imparted to the allyl radical during photolysis and the small impact parameter and reduced mass characterizing the loss of an H atom from an allyl radical to form allene + H. A photoionization efficiency (PIE) curve identified the major C 3 H 4 secondary dissociation products as allene. Comparison of the mass 40 signal in the TOF spectra at two photoionization energies showed that branching to H + propyne does not occur at near-threshold internal energies, indicating that the experimentally determined allyl f 2-propenyl radical isomerization barrier, which is lower than recent ab initio calculations of the barrier by ∼15 kcal/mol, is far too low.

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Section: Introductionmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

et al. 2002

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ChemInform Abstract: Possible Rearrangements Between Isomeric C3H5 Radicals

Ondruschka¹,

Ziegler²,

Zimmermann³

1987

ChemInform

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Ethylidencyclohexan ‐ Vorstufe für Allyl‐ und 1,2‐Dimethyl‐allylradikale in der Gasphase

Ondruschka¹,

Vorwerk²,

Remmler³

1990

J. Prakt. Chem.

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Ethylidenecyclohexane ‐ Precursor of Allyl and 1,2‐Dimethylallyl Radicals in the Gas Phase A systematic study of the thermolysis of ethylidenecyclohexane (1) and 1‐vinylcyclohexene (3) was made under VLPP‐MS‐conditions. The major fate of 1 is isomerization to 5‐methyl‐hepta‐1,5‐diene (2) which may then decompose to allyl (7) and 1,2‐dimethylallyl radical (6). The latter is highly unstable and therefore 6 is degraded to isoprene. Minor processes in thermolysis of 1 include further hydrogen elimination to 3 and double bond isomerization to 1‐ethylcyclohexene (4). Both cyclohexene derivates undergo most notably RDA‐fragmentation.

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Zu möglichen Umlagerangen zwischen isomeren C₃H₅-Radikalen

Cited by 11 publications

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Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

ChemInform Abstract: Possible Rearrangements Between Isomeric C3H5 Radicals

Ethylidencyclohexan ‐ Vorstufe für Allyl‐ und 1,2‐Dimethyl‐allylradikale in der Gasphase

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Zu möglichen Umlagerangen zwischen isomeren C3H5-Radikalen

Cited by 11 publications

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Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

Primary and Secondary Dissociation from Allyl Iodide Excited at 193 nm: Centrifugal Effects in the Unimolecular Dissociation of the Allyl Radical

ChemInform Abstract: Possible Rearrangements Between Isomeric C3H5 Radicals

Ethylidencyclohexan ‐ Vorstufe für Allyl‐ und 1,2‐Dimethyl‐allylradikale in der Gasphase

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Zu möglichen Umlagerangen zwischen isomeren C₃H₅-Radikalen