Activation energy requirements in hydrogen abstractions. Quantitative description of the causes in terms of bond energies and infrared frequencies

Zavitsas, Andreas A.

doi:10.1021/ja00763a041

Cited by 76 publications

(30 citation statements)

References 26 publications

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“…More recently, Zavitsas (20) has shown that f = 0.45 gives a value for the triplet repulsive term which is more consistent with a value obtained based on variational calculations, and this value has been adopted by Gilliom (11) and here. In eq.…”

Section: Bebo Calculationssupporting

confidence: 83%

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

Niedzielski¹,

Yano²,

Tschuikow‐Roux³

1984

Can. J. Chem.

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. 62, 899 (1984).The abstraction of hydrogen/deuterium from CH,CHDCI by ground state chlorine atoms produced photolytically from C12 has been investigated at temperatures betwen 280 and 368 K. The relative rates for the internal competition CH3CHDCI + C1+ CH3CDCI + HCl kH + CH3CHCI + DCI kD are found to conform to an Arrhenius rate law:These data, taken together with the external competition results for the C2HsCI/CH3CHDC1 system, in conjunction with the competitive results using CH4 as a primary reference, have yielded the rate constants (cm3 s-I):The relatively weak primary kinetic isotope effect, kH/kD, decreases with increasing temperature from 1 .8S5 at 280 K to 1.66 at 365 K. The results are compared with those obtained based on the BEBO method. While both the trend and the magnitude of the kinetic isotope effect are satisfactorily predicted, the activation energy is not. Introduction In a recent paper from this laboratory (1) the photochlorination of gaseous ethyl chloride and ethyl chloride-d, was examined. Kinetic data on the hydrogen and deuterium atom abstraction by photochemically generated chlorine atoms were obtained, and the magnitude of the overall kinetic isotope effect was established. In the present work these studies are extended to the photochlorination of ethyl chloride-1-d,. Our aim is twofold: firstly, to determine accurately the primary kinetic isotope effect and the absolute rate parameters by way of a suitable reference reaction, and, secondly, to compare these

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Section: Bebo Calculationssupporting

confidence: 83%

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

Niedzielski¹,

Yano²,

Tschuikow‐Roux³

1984

Can. J. Chem.

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“…Phenol is considerablv more reactive than BEBO method (27) calculations of these systems tentatively imply that the difference in activation energies could be as large as 5 kcal mol-'. Unfortunately these calculations are even more qualitative when they are extended to aromatic amines and thiophenols.…”

Section: Kineticsmentioning

confidence: 98%

Arrhenius Parameters for Reaction of the tert-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols

Chenier¹,

Furimsky²,

Howard³

1974

Can. J. Chem.

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Preexponential factors and activation energies are reported for the transfer of a hydrogen atom from phenol, β-naphthol, aniline, β-naphthylamine, thiophenol, and β-naphthalenethiol to a tertiary alkylperoxy radical ((CH3)3COO• and C2H5C(CH3)2OO•). The A-factors fall in the range 2 × 104 to 2 × 107 M−1 s−1 and increase in the order C6H5SH ~ β-C10H7SH ~ β-C10H7NH2 < C6H5NH2 ~ β-C10H7OH < C6H5OH while the activation energies fall in the range 1 to 5 kcal mol−1 and increase in the order C6H5SH ~ β-C10H7SH < β-C10H7NH2 ~ β-C10H7OH < C6H5OH ~ C6H5NH2. Differences in activation energies and preexponential factors are not consistent with a reaction mechanism which attributes low activation parameters solely to an equilibrium between the reactants and a hydrogen bonded free radical – reactant complex, followed by H-atom transfer within the complex.

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“…An additional important point is that the calculated activation enthalpy for simple HAT between a hydroxyl radical and water is similar to that found for the redox process between metal couples (DH a % 7.5 kcal mol À1 , see the Supporting Information for details); this suggests that the essence of the mechanism could be an intrinsic feature of water and not dependent on the metal centre. [31] If this assumption were correct, the PCET process might take place at longer distances. For both iron and chromium systems, we located TSs for HAT through four water molecules that involved the cleavage and formation of six O À H bonds in a single step ( Figure 6).…”

Section: Spin Complexes [Ma C H T U N G T R E N N U N G (H 2 O) 6 ] 2mentioning

confidence: 99%

The Role of Water‐Based Hydrogen Atom Wires in Long‐Range Electron‐Transfer Reactions in Aqueous Media for the Fe^II–Fe^III Self‐Exchange and Related Systems

Campaña

Buñuel

Cuerva

et al. 2013

Chemistry A European J

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Activation energy requirements in hydrogen abstractions. Quantitative description of the causes in terms of bond energies and infrared frequencies

Cited by 76 publications

References 26 publications

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

Arrhenius Parameters for Reaction of the tert-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols

The Role of Water‐Based Hydrogen Atom Wires in Long‐Range Electron‐Transfer Reactions in Aqueous Media for the Fe^II–Fe^III Self‐Exchange and Related Systems

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Activation energy requirements in hydrogen abstractions. Quantitative description of the causes in terms of bond energies and infrared frequencies

Cited by 76 publications

References 26 publications

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d1

Arrhenius Parameters for Reaction of the tert-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols

The Role of Water‐Based Hydrogen Atom Wires in Long‐Range Electron‐Transfer Reactions in Aqueous Media for the FeII–FeIII Self‐Exchange and Related Systems

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Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

Primary kinetic isotope effect in the gas phase photochlorination of ethyl chloride-1-d₁

The Role of Water‐Based Hydrogen Atom Wires in Long‐Range Electron‐Transfer Reactions in Aqueous Media for the Fe^II–Fe^III Self‐Exchange and Related Systems