Thermal unimolecular reactions of hydrocarbons

Frey, H. M.; Walsh, Robin

doi:10.1021/cr60257a004

Cited by 238 publications

(88 citation statements)

References 24 publications

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“…34; common variants are the modified Arrhenius form [35], or more complicated forms in which both the activation energy and pre-exponential factor are temperature-dependent (27,28). It is, of course, extraordinarily difficult to distinguish among these various forms Tor any particular set of experimental rate constants because this would require accurate measurements of the rates over very wide ranges of temperature (27), and to our knowledge, only three unimolecular reactions have been so studied.…”

Section: Appendixmentioning

confidence: 99%

A reformulation of the theory of unimolecular reactions

Yau¹,

Pritchard²

1978

Can. J. Chem.

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PRITCHARD. Can. J. Chem. 56, 1389(19783 The theory of unimolecular reactions is reformulated in a way which makes no reference t o the concepts of a transition state, a reaction coordinate, or of an activated complex: the present theory is based, instead, on a simple master-equation approach using the estimated positions and lifetimes of the rotation-vibration energy levels of the molecule. The fundamental basis of this reformulation is that the unimolecular rate is derived from the perturbation of the normal modes of internal relaxation of the reactant molecule by the microscopic reaction processes. The thermal decompositions of cyclobutane, cyclopropane, ethyl isocyanide, ethyl chloride, and methyl isocyanide are examined in detail, and it is shown that not only is the present theory much easier to use than is conventional RRKM theory, but also that it gives better results.An Appendix provides a set of algorithms required for these calculations. Un appendice fournit l'ensemble d'algorithmes requis pour ces calculs.[Traduit par le journal]

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Section: Appendixmentioning

confidence: 99%

A reformulation of the theory of unimolecular reactions

Yau¹,

Pritchard²

1978

Can. J. Chem.

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“…The usual ring-opening reactions should be accelerated by resonance stabilization of biradical intermediates [3-51 by the cyano group, and measurement of activation energies should permit an estimate to be made of the extent of this stabilization. In addition, it was possible that new types of reaction might occur, e.g., ring-expansion reactions similar to those observed for vinyl [3,4] and imino [6] cyclopropanes or migration of the cyano group as a pseudohalogen (cf. chlorine and bromine migration [3]).…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the reactions of cyclopropane derivatives. III. Gas‐phase unimolecular isomerization of cyclopropyl cyanide to the cyanopropenes

Luckraft

Robinson

1973

Int J of Chemical Kinetics

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Cyclopropyl cyanide isomerizes in the gas phase at 660"-760"K and 2-89 torr to give mainly cis-and trans-crotonitrile and ally1 cyanide, with traces of methacrylonitrile. The reactions are first order, homogeneous, and unaffected by the presence of radical-chain inhibitors. Overall:The rate constants are given by log,ok/sec-l = (14.59 f 0.13) -(252.5 + 1.8) kJ mole-'/2.303 R T where the error limits afe standard deviations. On the basis of a biradical mechanism, it is deduced that the -CH-CN radical center is resonance stabilized by ca. 30 kJ mole-'. Approximate equilibrium data are given for interconversion of the 1-and 3-cyanopropenes.

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“…The solvent effect observed in the present work could then indicate a protection of the hydroxylic hydrogen of DEHA by polar and protic solvents. Reaction (12), which will become important, at high BukNOH/BuiNO, explains the autoinhibition observed. The occurrence of reaction (13) could explain the lack of quantitative nitrone formation.…”

Section: Bimolecular Reactionsmentioning

confidence: 87%

“…The preexponential factor can be considered normal for a P-scission reaction of a free radical [12]. The value of the activation energy is com- kcal/mol.…”

Section: (6)mentioning

confidence: 99%

Reaction of di‐tert‐butylnitroxide radicals

Lissi

Rubio

Araya

et al. 1980

Int J of Chemical Kinetics

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Di-tert-hutylnitroxide (DTBN) is the simplest of the stable nitroxide radicals and is only consumed a t temperatures higher than 9OoC or in the presence of very reactive substrates. The pyrolysis of DTBN in solution gives, at least at low conversion, 2-methyl-2-nitrosopropane and di-tert-hutylnitroxide-tert-hutyl ether. The reaction involves, as the rate-limiting step, the cleavage of the C-N bond. This reaction takes place with an activation energy of 33 kcal/mol. DTBN is stable in the presence of styrene, aldehydes, hydrogen peroxide, wmethyl-N-ethyl nitrone, phenol, and triphenylmethane. On the other hand, it reacts readily with diethylhydroxylamine, ascorbid acid, ethanethiol, and hexanethiol. For the two former compounds the reaction involves a hydrogen transfer as the rate-determining step, and the reaction proceeds, a low conversion, with simple second-order kinetics. The reaction with the thiols is complex and shows a clear induction time.

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Thermal unimolecular reactions of hydrocarbons

Cited by 238 publications

References 24 publications

A reformulation of the theory of unimolecular reactions

A reformulation of the theory of unimolecular reactions

Kinetics of the reactions of cyclopropane derivatives. III. Gas‐phase unimolecular isomerization of cyclopropyl cyanide to the cyanopropenes

Reaction of di‐tert‐butylnitroxide radicals

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