Stabilities and lifetimes of fluoroalkyl iodide and fluoroallyl iodide collision complexes

White, R.W.P.; Smith, David J.; Grice, R.

doi:10.1021/j100112a011

Cited by 13 publications

(5 citation statements)

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“…This symmetrical angular distribution corresponds to a lifetime of the collision complex of many rotational periods, thus confirming that the slow component of IO scattering in Figure arises from a long-lived singlet OICH 2 Cl complex. The ratio of the lifetime τ to the rotational period τ rot may be estimated for the singlet OICH 2 Cl complex with a well depth E 0 of ∼155 kJ mol -1 from the RRKM formula: This yields τ ∼ 8τ rot for E = 46 kJ mol -1 when using a maximum initial orbital angular momentum L m of ∼140 ℏ, a moment of inertia I 2 * ∼1.2 × 10 -44 kg m 2 , a geometric mean vibrational frequency ν = 1.1 × 10 13 s -1 , and an effective number of modes s = 6 corresponding to the heavy atom motion with frequencies estimated from ab initio calculations 17 for OICH 3 and spectroscopic values 26 for CH 2 Cl. This situation assumes an equal probability of dissociation to products and back to reactants.…”

Section: Discussionmentioning

confidence: 99%

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

et al. 1998

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Reactive scattering of O(3P) atoms with CH2ICl molecules has been measured at initial translational energies E ∼ 46 and 17 kJ mol-1 using a supersonic beam of O atoms seeded in He and Ne buffer gases generated from a high-pressure microwave discharge source. At the higher initial translational energy, the IO product scattering can be resolved into two components; one showing forward and backward peaking with a product translational energy distribution peaking at low energy with a tail extending out to higher energy, and the other that peaks in the backward direction with higher product translational energy. At lower initial translational energy, the IO product scattering does not allow the resolution of two components but peaks in the backward direction with a higher product translational energy than for scattering in the forward hemisphere. The slow component is attributed to dissociation of a long-lived OICH2Cl complex formed by intersystem crossing from the initial triplet 3A‘‘ potential energy surface to the underlying singlet 1A‘ potential energy surface. The fast component is attributed to direct reaction over the triplet potential energy surface with the sharp backward peaking arising from reaction on the 3Π2 and 3Π1 spin multiplet surfaces in near collinear OICH2Cl configurations and the scattering in the sideways and forward directions arising from reaction on the 3A‘‘ Renner Teller surface in strongly bent configurations. The contribution of the slow component is approximately one-third that of the fast component to the total reaction cross section for IO product scattering.

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Section: Discussionmentioning

confidence: 99%

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

et al. 1998

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“…The ratio of the lifetime τ to the rotational period τ rot for the DOICl complex may be estimated from the RRKM formula This yields τ ∼ τ rot when using a maximum initial orbital angular momentum L m ∼ 170ℏ, a moment of inertia I * 2 ∼ 4 × 10 -45 kg m 2 , a mean vibrational frequency ν = 1.1 × 10 13 s -1 , and an effective number of modes s = 6, when the well depth of the DOICl complex is taken as E 0 ∼ 80 ± 20 kJ mol -1 . This calculation assumes that the DOICl complex dissociates with roughly equal probability to form reaction products and to reform the reactants.…”

Section: Discussionmentioning

confidence: 99%

Reactive Scattering of OD Radicals with ICl and Br₂ Molecules at Initial Translational Energy E ∼ 90 kJ mol^-1

et al. 1997

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Reactive scattering of OD radicals with ICl and Br2 molecules has been studied at an initial translational energy E ∼ 90 kJ mol-1 using a supersonic beam of OD radicals seeded in He buffer gas generated from a high-temperature radio frequency discharge source. The center-of-mass angular distribution of DOI scattering from OD + ICl shows sharp forward and backward peaking with the relative intensity of the backward peak being lower by a factor ∼0.6 ± 0.1. The DOBr scattering from OD + Br2 shows broader peaking in the forward direction declining to a lower intensity ∼0.8 ± 0.2 in the backward direction. In both cases the product translational energy distributions peak at low energy with a tail extending out to higher energy. Comparison with the predictions of phase space theory indicates that the OD + ICl reaction proceeds via a DOICl collision complex with a lifetime of approximately one rotational period, while the OD + Br2 reaction shows evidence for the migration of the OD radical between the Br atoms of a DOBrBr complex. The DOICl complex corresponds to a significant well of depth E 0 ∼ 80 kJ mol-1 on the potential energy surface for the OD + ICl reaction while the potential energy surface for the OD + Br2 reaction also supports a shallow minimum.

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“…The temperature dependence reveals low activation energies and high preexponential factors, suggesting the presence of attractive interactions between the two reactants and the formation of intermediate RI−Cl adducts (R = alkyl group). This behavior has been also observed in reactions of bromoalkanes with either Cl or F atoms , and in reactions of iodinated compounds with F atoms. , A comparison among the experimental or theoretically derived stabilities of the corresponding RX−Y (X = Br, I; Y = F, Cl) adducts, ,,,, reveals that the strength of these interactions is favored by low ionization potentials of the parent RX halides ( X = Br, I) and large electronegativity differences between X and the incoming Y (F, Cl) halogen atoms. Thus, an apparently bimolecular reaction may have pressure-dependent contributions from more complex reaction schemes which affect the overall kinetics as well as the reaction mechanism. ,,, At sufficiently high temperatures (related to the RX-Y bond strengths) the adducts possess very short lifetimes and these contributions are negligible.…”

Section: Discussionmentioning

confidence: 77%

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals

et al. 2008

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The gas-phase reaction of atomic chlorine with diiodomethane was studied over the temperature range 273-363 K with the very low-pressure reactor (VLPR) technique. The reaction takes place in a Knudsen reactor at pressures below 3 mTorr, where the steady-state concentration of both reactants and stable products is continuously measured by electron-impact mass spectrometry. The absolute rate coefficient as a function of temperature was given by k = (4.70 +/- 0.65) x 10-11 exp[-(241 +/- 33)/T] cm3molecule-1s-1, in the low-pressure regime. The quoted uncertainties are given at a 95% level of confidence (2sigma) and include systematic errors. The reaction occurs via two pathways: the abstraction of a hydrogen atom leading to HCl and the abstraction of an iodine atom leading to ICl. The HCl yield was measured to be ca. 55 +/- 10%. The results suggest that the reaction proceeds via the intermediate CH2I2-Cl adduct formation, with a I-Cl bond strength of 51.9 +/- 15 kJ mol-1, calculated at the B3P86/aug-cc-pVTZ-PP level of theory. Furthermore, the oxidation reactions of CHI2 and CH2I radicals were studied by introducing an excess of molecular oxygen in the Knudsen reactor. HCHO and HCOOH were the primary oxidation products indicating that the reactions with O2 proceed via the intermediate peroxy radical formation and the subsequent elimination of either IO radical or I atom. HCHO and HCOOH were also detected by FT-IR, as the reaction products of photolytically generated CH2I radicals with O2 in a static cell, which supports the proposed oxidation mechanism. Since the photolysis of CH2I2 is about 3 orders of magnitude faster than its reactive loss by Cl atoms, the title reaction does not constitute an important tropospheric sink for CH2I2.

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Stabilities and lifetimes of fluoroalkyl iodide and fluoroallyl iodide collision complexes

Cited by 13 publications

References 4 publications

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

Reactive Scattering of OD Radicals with ICl and Br₂ Molecules at Initial Translational Energy E ∼ 90 kJ mol^-1

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals

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Stabilities and lifetimes of fluoroalkyl iodide and fluoroallyl iodide collision complexes

Cited by 13 publications

References 4 publications

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(3P) + CH2ICl Reaction

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(3P) + CH2ICl Reaction

Reactive Scattering of OD Radicals with ICl and Br2 Molecules at Initial Translational Energy E ∼ 90 kJ mol-1

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH2I2 and the Oxidation Mechanism of CH2I Radicals

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Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

Role of Renner Teller and Spin−Orbit Interaction in the Dynamics of the O(³P) + CH₂ICl Reaction

Reactive Scattering of OD Radicals with ICl and Br₂ Molecules at Initial Translational Energy E ∼ 90 kJ mol^-1

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals