Hydrogen atom abstraction reaction by H atoms in γ-radiolysis and U.V.-photolysis of alkane mixtures at 4K

Kinugawa, Kazuhisa; Miyazaki, Tsuyoshi; Hase, Hirotomo

doi:10.1016/0146-5724(77)90042-5

Cited by 16 publications

(6 citation statements)

References 33 publications

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“…After completing the work, similar experiments on the irradiation temperature effects on selective formation of solute radicals in alkane mixtures have been reported by Kinugawa et al 15 They have confirmed our previous results3 that the selective formation of solute radicals upon radiolysis is greatly suppressed at 4.2 K. On the other hand, contrary to the present results they have reported that the selective formation of solute radicals is not suppressed at 4.2 K in the case of photolysis of HI in neopentane containing a small amount of isobutane.…”

Section: Supplemental Experimentssupporting

confidence: 59%

Irradiation temperature effects on hydrogen atom reactions upon radiolysis and photolysis at 4.2 and 77 K of neopentane containing various additives as studied by electron spin resonance

Iwasaki¹,

Muto²,

Toriyama³

et al. 1979

J. Phys. Chem.

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26) P. Neta (private communication) has recorded the ESR spectrum of bpyH2+• at pH 2.3 and 0. The spectrum consists of nine groups of lines of varying Intersltles; the seven central groups are Identical at both pH values while the two extreme groups, although of tow Intensity, appear to be somewhat different at the two pH values which could Indicate the onset of a pKa at the higher acidity. ( 27) M. Simic and E.

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Section: Supplemental Experimentssupporting

confidence: 59%

Irradiation temperature effects on hydrogen atom reactions upon radiolysis and photolysis at 4.2 and 77 K of neopentane containing various additives as studied by electron spin resonance

Iwasaki¹,

Muto²,

Toriyama³

et al. 1979

J. Phys. Chem.

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“…i=l It is noted that if fe6/fe7 = 0, F becomes as follows: (15) 1=1 and if k3/ki = 1, F becomes as follows:…”

Section: Resultsmentioning

confidence: 99%

A simple model for hydrogen atom reactions in neopentane-cyclohexane mixtures irradiated at 4.2 K

Iwasaki¹,

Toriyama²

1979

J. Phys. Chem.

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In this paper, a simple model is given to explain why hydrogen atoms produced in crystalline neopentane at 77 K have a high probability of reacting with dilute solute molecules, whereas at 4.2 K they abstract hydrogen from neopentane matrix molecules. The model is based on the following assumptions: at 77 K hydrogen atoms which do not undergo short-range hot abstractions migrate until they encounter a solute molecule, and abstract hydrogen from it. At 4.2 K the hydrogen atoms which would be mobile at 77 K are immobilized at their place of birth and eventually abstract only from one of the molecules in the cage wall surrounding each hydrogen atom. The experimental data at 4.2 K are compared with estimates of the solute radical yields for different assumed values of (a) the fraction of hydrogen atoms which undergo short-range hot abstraction; (b) the ratio of the rate constants for the reaction of immobilized hydrogen atoms with a matrix and a solute molecule; and (c) the number of molecules in the cage wall. By this comparison plausible numerical values are obtained for each of these parameters.

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“…Nearly 30 years ago Miyazaki et al found that H atoms react several hundreds times faster with the solute alkane than the solvent neopentane to form solute alkyl radicals when H atoms are produced by the radiolysis of neopentane in neopentane−alkane mixtures at 77 K . The selective reaction is, however, suppressed at 4 K. , Although H atoms have never been observed by ESR in irradiated neat neopentane−alkane mixtures even at 4 K, the detailed studies by Miyazaki et al have concluded that H atoms produced by radiolysis react with solute alkane by a hydrogen atom abstraction reaction due to atomic tunneling . Let us consider the following reactions 1 and 2: Since both neopentane (neo-C 5 H 12 ) and ethane (C 2 H 6 ) molecules are composed of primary C−H bonds, the difference in the energy barrier height for the abstraction reactions between 1 and 2 is very small.…”

Section: Introductionmentioning

confidence: 99%

ESR, ENDOR, and ESEEM Spectroscopy Study on the Local Structure and Motion of Reactants: Highly Selective Tunneling Radical Abstraction in a Neopentane−Ethane Mixture

et al. 2001

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Local structures and motions of radical reactants in highly selective tunneling abstraction reaction in neopentane-ethane mixture are investigated with CW-ESR, ENDOR, and ESEEM spectroscopy at different temperatures. H atoms produced by the radiolysis of neo-C 5 H 12 in the neo-C 5 H 12 -C 2 H 6 (2 mol %) mixtures above 40 K react selectively with the solute C 2 H 6 to give ethyl radicals. The selective reaction is suppressed below 30 K. The local structures of neopentane matrix around neopentyl and ethyl radicals are approximately the same in the temperature range from 4.4 to 45 K. Although neopentyl radicals are rigidly trapped below 100 K, ethyl radicals in neopentane matrix begin to librate even at 6 K and increase the degree of motion up to 30 K. Finally, the librating motion of the ethyl radicals in neopentane matrix is vigorous above 40 K. The ethane molecule can take more favorable orientation for the hydrogen abstraction reaction by H atoms than rigid neopentane molecules by the vigorous libration motion, resulting in the selective reaction with H atoms.

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Hydrogen atom abstraction reaction by H atoms in γ-radiolysis and U.V.-photolysis of alkane mixtures at 4K

Cited by 16 publications

References 33 publications

Irradiation temperature effects on hydrogen atom reactions upon radiolysis and photolysis at 4.2 and 77 K of neopentane containing various additives as studied by electron spin resonance

Irradiation temperature effects on hydrogen atom reactions upon radiolysis and photolysis at 4.2 and 77 K of neopentane containing various additives as studied by electron spin resonance

A simple model for hydrogen atom reactions in neopentane-cyclohexane mixtures irradiated at 4.2 K

ESR, ENDOR, and ESEEM Spectroscopy Study on the Local Structure and Motion of Reactants: Highly Selective Tunneling Radical Abstraction in a Neopentane−Ethane Mixture

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