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Rosana M. Romano, Joanna Czarnowski

Kinetics and Mechanism of the Thermal Gas-Phase Reaction between NO₂ and Trifluorobromoethene, CF₂CFBr

The reaction of NO₂ with CF₂CFBr has been studied at 322.6, 333.1 and 343.4 K, using a conventional static system. The initial pressure of CF₂CFBr was varied between 26.9 and 75.5 torr and that of NO₂ between 9.6 and 41.9 torr. Two experiments were made in presence of CF₄ used as inert gas at the pressure of 238.8 and 334.6 torr, respectively. Five products were observed: CF₂(NO₂)C(O)F, CF₂(NO₂)CFBr(NO₂), BrNO, Br₂ and NO. The distribution of the products CF₂(NO₂)C(O)F and CF₂(NO₂)CFBr(NO₂) was independent of the initial pressure of the reactants and the total pressure, but the relation CF₂(NO₂)C(O)F/CF₂(NO₂)CFBr(NO₂) increased with the temperature. The reaction is homogeneous and independent of the total pressure. The following mechanism was postulated to explain the experimental results:

1. CF₂CFBr + NO₂ → CF₂(NO₂)C^•FBr
2. CF₂(NO₂)C^•FBr + NO₂ + M → CF₂(NO₂)CFBrNO₂ + M
3. CF₂(NO₂)C^•FBr + NO₂ → CF₂(NO₂)C(O)F + BrNO
4. 2BrNO ↔ Br₂ + 2NO

k₁ = (1.51 ± 0.45) × 10⁶ exp(−(10.88 ± 1) kcal mol⁻¹/RT) dm³ mol⁻¹ s⁻¹.

Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0942-9352
Volume: 219, 06/2005
Pages: 849 - 864

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