Far Ultraviolet Photochemistry of Organic Compounds

Ausloos, P.; Lias, Sharon G.

doi:10.1007/978-94-010-2153-1_28

Cited by 9 publications

(1 citation statement)

References 27 publications

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“…1 There appears to be a modest effect of the adjacent ethyl groups analogous to the effect of methyl substitution noted in ref 7. In general, photochemical studies have shown that that excess energy in excited alkanes is highly localized around tertiary carbon atoms and leads to the preferential rupture of C-H and C-C bonds adjacent to the tertiary site. 19,20 Because C-C rupture occurs only as the result of primary processes, the high yields of the radicals produced radiolytically by the rupture of the C-C bonds adjacent to the tertiary site demonstrate that the energy deposited by ionizing radiation is similarly localized at tertiary sites.…”

Section: Discussion and Summarymentioning

confidence: 99%

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Schüler

Wojnárovits

2003

J. Phys. Chem. A

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Gel permeation chromatography has been applied to iodine scavenging studies of the distribution of radicals produced in the radiolysis of symmetrically branched hydrocarbons 2,3-dimethylbutane, 2,4-dimethylpentane, and 3-ethylpentane. The principal iodides observed are those expected as a result of simple bond rupture. In the case of 2,3-dimethylbutane all five expected iodides are readily resolvable and it is shown that the loss of H from a tertiary position is favored over loss from a primary position by a factor of ∼10. A similar ratio is also observed for 2,4-dimethylpentane. The higher ratio of 15 observed for 3-ethylpentane indicates a dependence on the number of tertiary sites on the alkane. The relative yield of ∼3.3 for the loss of secondary and primary H atoms from 2,4-dimethylpentane and 3-ethylpentane is similar to that for normal alkanes, indicating a negligible effect of the adjacent tertiary carbon. In all three cases the rupture of terminal C-C bonds is relatively infrequent with C-C rupture occurring preferentially at the bonds adjacent to the tertiary carbon.

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Section: Discussion and Summarymentioning

confidence: 99%

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Schüler

Wojnárovits

2003

J. Phys. Chem. A

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Kinetic Isotope Effects for Hydrogen Abstraction from Various Saturated Hydrocarbons by Deuterium Atoms in the Gas Phase

Fujisaki

Gäumann

Ruf

1986

Ber Bunsenges Phys Chem

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Using deuterium atoms produced in the radiolysis of heavy water vapor, the kinetic isotope effects kH/kD were determined by the isotope competitive method for the abstraction reaction D' + RH(R'D)--+HD(D2) + R.(R'), where RH is an alkane and R'D is the corresponding perdeuterated alkane. The alkanes RH investigated include isohutane, 2,3,4-trimethylpentane, neopentane, cyclopentane, cyclohexane, cycloheptane, and n-heptane. The results were represented in terms of the Arrhenius-type expression kH/kD = AH/AD exp((ED -EH) (kJ mol-')/R T ) , over the temperature range 363 -473 K. The pre-exponential factor ratios AH/AD vary from 0.36 for neopentane to 0.70 for 2,3,4-trimethylpentane, the ED -EH values from 6.4 for 2,3,4-trimethylpentane to 10.4 kJ mol-' for neopentane.The variation in the ED -EH values was correlated with the bond strength of the C -H bond being broken. The deuterium and hydrogen atoms, as the attacking species, are found to show essentially the same magnitude of the kinetic isotope effects in the hydrogen abstraction from a given alkane. The theoretical calculations of the isotope effects have been carried out on the basis of transition-state theory combined with the London-Eyring-Polanyi-Sato potential energy surface. Good agreement was obtained between experiment and theory, when tunnel effects were taken into consideration.

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Physicochemical Properties of Deuterated Compounds. 8^th Communication. The kinetic isotope effect for the reaction of hydrogen atoms with methylcyclohexane and perdeuteromethylcyclohexane in the gas phase

Fujisaki

Ruf

Gäumann

1985

Helvetica Chimica Acta

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of H abstraction from primary, secondary, and tertiary C-H bonds in methylcyclohexane is taken into consideration in the interpretation of the Arrhenius-type expression obtained. Theoretical interpretation of the kinetic isotope effect has been achieved on the basis of the transition-state theory and a semiempirical London-EyringPolunyi-Suto potential-energy surface. The tunnel effect is found to play a role in the H-abstraction. Several methods for estimating the tunnel correction factors have been discussed.

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Far Ultraviolet Photochemistry of Organic Compounds

Cited by 9 publications

References 27 publications

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Kinetic Isotope Effects for Hydrogen Abstraction from Various Saturated Hydrocarbons by Deuterium Atoms in the Gas Phase

Physicochemical Properties of Deuterated Compounds. 8^th Communication. The kinetic isotope effect for the reaction of hydrogen atoms with methylcyclohexane and perdeuteromethylcyclohexane in the gas phase

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Far Ultraviolet Photochemistry of Organic Compounds

Cited by 9 publications

References 27 publications

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Radical Yields in the Radiolysis of Branched Hydrocarbons: Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Kinetic Isotope Effects for Hydrogen Abstraction from Various Saturated Hydrocarbons by Deuterium Atoms in the Gas Phase

Physicochemical Properties of Deuterated Compounds. 8th Communication. The kinetic isotope effect for the reaction of hydrogen atoms with methylcyclohexane and perdeuteromethylcyclohexane in the gas phase

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Physicochemical Properties of Deuterated Compounds. 8^th Communication. The kinetic isotope effect for the reaction of hydrogen atoms with methylcyclohexane and perdeuteromethylcyclohexane in the gas phase