Collisional Deactivation of Vibrationally Excited 2-Pentyl Radicals

Georgakakos, J. H.; Rabinovitch, B. S.; McAlduff, E. J.

doi:10.1063/1.1673267

Cited by 24 publications

(4 citation statements)

References 27 publications

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“…This value is ~1 kcal mol-1 less than for CPn•, and since it is not apparent why ring opening of CHx• should not occur relative to CPn•, we believe that opening does occur, and that the steady-state concentration of acyclic radicals is too low to be detected. Reaction 14 which leads to a radical with more strain energy than reaction 18 may actually proceed faster because, in this case, the radical center is off the ring; although | rs| is greater for the five-membered ring transition state than for the six-membered transition state, the situation is reversed for the relative values of Els• In fact, reaction 14 has been found to be faster than reaction 18 in liquid phase cyclizations. 22 If all of the product radical cyclized via reaction 14, and if the direct isomerization were not important, Eo would be ~32 kcal mol-1, by analogy to CPn•.…”

Section: IIImentioning

confidence: 99%

Ring opening and isomerization of a series of chemically activated cycloalkyl radicals

Stein¹,

Rabinovitch²

1975

J. Phys. Chem.

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Section: IIImentioning

confidence: 99%

Ring opening and isomerization of a series of chemically activated cycloalkyl radicals

Stein¹,

Rabinovitch²

1975

J. Phys. Chem.

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“…In a recent series of papers [3,4] Troe has shown that for a simple exponential transition probability function it is possible to derive an analytical expression for k0]', the thermal low pressure non-equilibrium rate constant for the vibrational decomposition of a molecule. Support for this type of function has been provided by a number of experimental studies on low pressure unimolecular reactions [5,6] and on vibrational-rotational 'relaxation [7]. Additional support is to be found in a recent series of classical trajectory calculations [8,9].…”

Section: Introductionmentioning

confidence: 91%

“…q(E, E') dE=l (5) --oo and it also obeys microscopic reversibiiity in the sense that q(E, E') exp (-E'/k T)=q(E', E) exp (-E/k T). (6) Equation (6) assumes that the vibrational density of states is constant and independent of energy. This is true for a diatomic harmonic oscillator which is the only Energy transfer in thermal reactions 157 type of molecule that we are concerned with in this paper.…”

Section: [2 + (7/kt)]mentioning

confidence: 99%

A Monte Carlo study of energy transfer in thermal unimolecular reactions: an application to diatomic dissociation

Stace

1979

Molecular Physics

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The Monte Carlo method has been used to develop a model that stimulates the low pressure, non-equilibrium unimolecular decomposition of a diatomic molecule. Through the inversion of a simple exponential transition probability function, expressions have been derived for generating random energy jumps. These energy jumps correspond to energy transitions induced through single collision events in an unspecified heat bath gas. A version of the model involving only vibrational energy jumps, reproduces the rate constants calculated from a corresponding analytical solution. For a more realistic model, involving rotational and vibrational energy jumps, the results indicate, that when vibrational energy transfer is inefficient, those molecules that dissociate are rotationally excited. Furthermore, the vibrational energy states of the non-reactive molecules are extensively depleted down to quite low energies, an effect that arises from dissociation through rotational excitation.

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“…Since 0 2 / 0 1 for the pentene-1 system would be approximately 1.5 and with kl =: 1.5 X lo7 sec-' [5], kI3 will be approximately 6 X lo5 sec-l.…”

Section: H F I-pentene Systemmentioning

confidence: 99%

Communication to the editor pentyl radical isomerizations: Evidence for a 1,2 or 1,3 hydrogen migration

Tardy¹

1974

Int J of Chemical Kinetics

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Vibrationally excited pentyl-1, -2, and -3 radicals were formed selectively by the addition of thermal H atoms to the various pentene isomers with approximately47 kcal/mole of vibrational energy. Decomposition products other than those expected, along with their pressure dependences, support the fact that either 1,2 or 1,3 hydrogen migrations with either a 3-or 4-member cyclic transition state is occurring with a k, of approximately 3 X lo5 or 6 X lo5 sec-I. A corresponding critical energy of 33 or 31 kcal/mole is found.There has been recent interest in the migration of hydrogen atoms in alkyl radicals [ 1-81. Both collisional (thermal) and external (chemical) activation methods have been used to form the alkyl radicals. Previous work [2, 3,6,7) has shown that 1,4 and 1,5 hydrogen shifts are measurable and occur via 5-and 6 member cyclic transition states (5MTS and 6MTS). 1,2 and 1,3 hydrogen shifts have not been substantiated [8], generally because they are of relatively minor importance. These processes are not observed in thermal systems since they have high activation energies and thus will not compete with low activation processes.In this work pentyl-2/pentyl-3 and pentyl-2/pentyl-1 radicals were initially formed by the addition of thermal hydrogen atoms to pentene-2 (both czs and trans independently) and pentene-1, respectively, with approximately 47 kcal/mole of bibrational excitation. The formed radicals have between 5 and 8 kcal/mole more vibrational energy than the pentyl radicals studied by Watkins and coworkers [3]. Using the nomenclature of Rabinovitch and coworkers [2], Watkins observed a 5sp isomerization involving a 5MTS in which a secondary C-H bond is broken and a primary C-H bond is formed (a slightly exothermic reaction) with a critical energy of 18 kcal/mole; the reverse has been observed in this study. Neither a 4sp (exothermic), 4ps, or 3ss isomerization have been previously reported. The purpose of this communication is to present qualitative and semiquantitative evidence for a 1,3 or possibly a 1,2 hydrogen shift and the corresponding critical energies.

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Collisional Deactivation of Vibrationally Excited 2-Pentyl Radicals

Cited by 24 publications

References 27 publications

Ring opening and isomerization of a series of chemically activated cycloalkyl radicals

Ring opening and isomerization of a series of chemically activated cycloalkyl radicals

A Monte Carlo study of energy transfer in thermal unimolecular reactions: an application to diatomic dissociation

Communication to the editor pentyl radical isomerizations: Evidence for a 1,2 or 1,3 hydrogen migration

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