Quantum mechanical and kinetic studies of the reaction of methyl radicals with molecular bromine

Drougas, Evangelos; Papayannis, Demetrios K.; Kosmas, Agnie M.

doi:10.1016/s0166-1280(02)00699-1

Cited by 5 publications

(3 citation statements)

References 38 publications

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“…The highest level ab initio computations of which we are aware for the analogous CH 3 • + Br 2 reaction gave results very similar to those for the chlorine transfer. A collinear prereaction complex, TS, and postreaction complex were all identified.…”

Section: Introductionsupporting

confidence: 59%

Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Trisubstituted Carbon-Centered Radicals with Molecular Halogens

Poutsma

2012

J. Org. Chem.

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Rate constants for the reaction (R'(3)C(•) + X(2) → R'(3)CX + X(•); X = F, Cl, Br, I) are reviewed. Because of curved Arrhenius plots and negative E(X) values, empirical structure-reactivity correlations are sought for log k(X,298) rather than E(X). The well-known poor correlation with measures of reaction enthalpy is demonstrated. The best quantitative predictor for R'(3)C(•) is Σσ(p), the sum of the Hammett σ(p) constants for the three substituents, R'. Electronegative substituents with lone pairs, such as halogen and oxygen, thus appear to destabilize the formation of a polarized prereaction complex and/or TS ((δ+)R- - -X- - -X(δ-)) by σ inductive/field electron withdrawal while simultaneously stabilizing them by π resonance electron donation. The best quantitative predictor of the reactivity order of the halogens, I(2) > Br(2) ≫ Cl(2) ≈ F(2), is the polarizability of the halogen, α(X(2)). For the data set of 60 rate constants which span 6.5 orders of magnitude, a modestly successful correlation of log k(X,298) is achieved with only two parameters, Σσ(p) and α(X(2)), with a mean unsigned deviation of 0.59 log unit. How much of this residual variance is the result of inaccuracies in the data in comparison with oversimplification of the correlation approach remains to be seen.

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Section: Introductionsupporting

confidence: 59%

Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Trisubstituted Carbon-Centered Radicals with Molecular Halogens

Poutsma

2012

J. Org. Chem.

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“…They have found the CH 3 + Br 2 reaction to proceed through a shallow pre-reaction complex (with ~4 kJ mol -1 stabilization energy) in the entrance channel, followed by a low barrier (~1 kJ mol -1 ) transition state structure, but unlike in our case, they have also mapped a post-reaction complex, CH 3 Br…Br, in the exit channel formed with a substantial amount of excess energy [15]. The microcanonical RRKM and QCT computations have supplied rate coefficients in good agreement with experiment [16].…”

Section: Drougas and Co-workers Have Studied This Reaction At The Ccsmentioning

confidence: 56%

“…As far as we know, CH 3 + Br 2 is the only polyatomic free radical + Br 2 reaction that has been the subject of quantum chemical and theoretical reaction kinetic investigations [15].…”

Section: Theoretical Resultsmentioning

confidence: 99%

Kinetics and mechanism of the reaction of acetonyl radical, CH3C(O)CH2, with Br2

Zügner

Szabó

et al. 2013

Chemical Physics Letters

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The low pressure fast discharge flow method with laser induced fluorescence detection of CH 3 C(O)CH 2 was employed to study the kinetics of the reaction CH 3 C(O)CH 2 + Br 2 → CH 3 C(O)CH 2 Br + Br (1) at 298, 323 and 365 K. The rate coefficient at room temperature is k 1 = (2.33 ± 0.04 (2σ)) × 10 -12 cm 3 molecule -1 s -1 , which increases slightly with increasing temperature. Quantum chemistry (G2) and theoretical rate theory (conventional TST) computations have supplied results in qualitative agreement with experiment. The relatively slow rate of reaction (1) can be due to the resonance stabilization of the acetonyl radical.

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Kinetics and mechanism of CH3Br, CHF2Br, and C2HF4Br photolysis in the presence of dioxygen under the action of λ = 253.7 nm light

et al. 2014

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Quantum mechanical and kinetic studies of the reaction of methyl radicals with molecular bromine

Cited by 5 publications

References 38 publications

Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Trisubstituted Carbon-Centered Radicals with Molecular Halogens

Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Trisubstituted Carbon-Centered Radicals with Molecular Halogens

Kinetics and mechanism of the reaction of acetonyl radical, CH3C(O)CH2, with Br2

Kinetics and mechanism of CH3Br, CHF2Br, and C2HF4Br photolysis in the presence of dioxygen under the action of λ = 253.7 nm light

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