The Reactions of Methyl Radicals.

Trotman‐Dickenson, A. F.; Steacie, E. W. R.

doi:10.1021/j150489a014

Cited by 40 publications

(44 citation statements)

References 21 publications

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“…Recently a simple correlation has been described for such reactions involving small radicals (16 where E is the activation energy for the reaction and D l and D2 are the C-H bond dissociation energies for AH and CH4, respectively. For reaction [4], taking D l = 100 kcal mol-' and D2 = 104 kcal mol-I , E = 11.7 kcal mol-' in good agreement with the value recommended by Kerr and Moss. For reaction [3], setting E = 15.5 kcal mol-' leads to a value of 106 kcal mol-' for D l .…”

Section: 3rtsupporting

confidence: 81%

“…Reaction [4] (Fig. 3) obtained by combining the present measurement of the ratio k,/k3 with values of k4 obtained from the expression proposed by Fume and Pacey and the evaluated Arrhenius expression of Kerr and Moss.…”

Section: From Eq [5] the Correction Factor Ismentioning

confidence: 80%

“…Although rate constants for the transfer reaction with several olefins have been reported, values of the rate constant for abstraction from ethylene are conspicuously absent. Only two measurements have been reported, one relative to abstraction from acetone (4) and the other relative to acetaldehyde (5). No measurements have been reported above 833 K. Nevertheless this reaction is important in many thermal reactions of hydrocarbons over a wide range of temperatures and a reliable value for the rate constant is crucial in the evaluation of mechanisms through 'Present address: Department of Chemistry, University of Benin, Benin City, Nigeria.…”

Section: Introductionmentioning

confidence: 99%

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Relative rate constants for abstraction of hydrogen by methyl radicals from ethane and from ethylene

Ahonkhai¹,

Back²

1988

Can. J. Chem.

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This paper is dedicated to Professsor J . A . Morrison S. I. AHONKHAI and M. H. BACK. Can. J. Chem. 66,578 (1988). A method is described for the measurement of relative rate constants for abstraction of hydrogen by methyl radicals from ethane and from ethylene based on the effect of the addition of small quantities of ethane on the rates of formation of products in the thermal reactions of ethylene. The ratio of rate constants for reactions over the temperature range 673-733 K was given by the following expression: 3500 * 500 log k4lk3 = 0.0 2 0.1 + 2.3RT (R = 1.987 cal mol-I deg-I). Using a value of k4 from the literature the following expression was obtained for k3, over the same range of temperature:It was concluded that a previous measurement of k3 in a lower range of temperature was too close to the value of k4

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Section: 3rtsupporting

confidence: 81%

Section: From Eq [5] the Correction Factor Ismentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

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Relative rate constants for abstraction of hydrogen by methyl radicals from ethane and from ethylene

Ahonkhai¹,

Back²

1988

Can. J. Chem.

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“…Trotinan-Dickenson and Steacie (8) have demonstrated that the facility with xvhich a hl-drogen atom may be abstracted from a hydrocarbon increases in the order primary, secondary, and tertiary. In a compound containing more than one type it is a t once apparent that the measured E is a coillposite activation energy.…”

Section: T a B L E I1 Comparison Of Results Obtained I N Various Invementioning

confidence: 99%

“…As these are stable thermally up to 250' C. (1, 4) [81 Evidence for a reaction analogous to [7] and [8] accounting for the fate of the radical CHzN = NCH3 was obtained in the study of the photolysis of azomethane alone (5). A disproportionation reaction between butyl radicals may also occur although indirect evidence suggests that the corresponding unsymmetrical process involving a methyl does not take place (7).…”

Section: T a B L E I1 Comparison Of Results Obtained I N Various Invementioning

confidence: 99%

The Reaction of Methyl Radicals With Isobutane

Jones¹,

Steacie²

1953

Can. J. Chem.

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An investigation is reported of the reaction of methyl radicals, produced in the photochemical decomposition of azomethane, with isobutane. 'l'lle energy of activation of this process was found to be 6.7 f 0.8 kcal./mole, assuming that the combination of methyl radicals has a n activation energy of zerci. From some experiments with n-butane, a value of 9 f 1 kcal./mole was obtained. INTRODUCTION.-\ recent study of the photolysis of azomethane (5) has shown that it may be used as a source of meth>.l radicals for an investigation of reactions of the type C H s + R H -+ C H I + R where RH is an); hydrogen containing compound. The choice of suitable compounds is, however, limited as the activation energy of hydrogen abstraction from azomethane itself is low. Since the method of investigation involves the determination of rate differences, the velocities of the two competitive reactions must be of roughly the same order of magnitude if quantitative results are required. Isobutane was chosen in the first instance as a simple hydrocarbon containing a tertiary carbon-hydrogen bond, where there is greater ease of abstraction (6, 7) than from a corresponding primary or secondary bond. E X P E R I M E N T A LThe apparatus and analytical procedure have been described elsewhere (5). The nitrogen-methane and ethane fractions were analyzed by the mass spectrometer and there was no evidence that the latter were contaminated with isobutane.The light source was a I-Ianovia S-500 medium pressure mercury arc and the collin~ated light beam had a volume within the quartz reaction cell of 110 cc. The cell volume was 170 cc. Two filters were used to cut out the short ultraviolet wave lengths. Filter A , a Corning filter No. 2-37 or 586, was opaque to wave lengths below 3150 A and had a transmission such that 96% of the absorbed radiation was the 3660 lines. Filter B was a Corning filter No. 0-53 or 774 and limited the incident radiation to wave lengths greater than 2800 a.The azomethane was a sample that had been prepared previously ( 5 ) . I t was kept as a liquid a t -78O C., vapor pressure 6.6 rnm., in a trap darkened to exclude daylight. Research Grade isobutane, obtained from the Phillips Petroleutn Company, was found t o contain traces of methane and ethane ( N 0.05 mole yo) which were sufficient to cause errors of several per cent in the analysis of the reactiorr products. The samples used were, therefore, introhfanzrscript received Febrzrary 10, 1953.

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