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Author(s):   Yu, H.; Mackie, J.C.; Kennedy, E.M.; Dlugogorski, B.Z.
Title:   Experimental and quantum chemical study of the reaction CF2+CH3 <-> CF2CH3 -> CH2=CF2+H: A key mechanism in the reaction between methane and fluorocarbons
Journal:   Ind. Eng. Chem. Res.
Volume:   45
Page(s):   3758 - 3762
Year:   2006
Reference type:   Journal article
Squib:   2006YU/MAC3758-3762

Reaction:   ·CF2 + ·CH3CH2=CF2 +
Reaction order:   2
Temperature:   700 - 2000 K
Pressure:  1.33E-3 - 13.33 bar
Rate expression:   1.07x10-11 [cm3/molecule s] (T/298 K)-0.21
Category:  Theory
Data type:   Ab initio
Experimental procedure:   Flow tube - Data taken vs distance
Excitation technique:   Thermal
Time resolution:   By end product analysis
Analytical technique:   GC-MS
Comments:   The reaction of CHClF2 with CH3Br was studied over the temperature range of 773-1123 K at atmospheric pressure in an alumina tubular reactor and the authors hypothesize that the observed CH2=CF2 is formed via the CF2 + CH3 reaction. The authors investigated the potential energy surface for the reaction via both density functional and MP2 methods. They conclude that CF2CH3 is formed as an intermediate but undergoes essentially no stabilization under the reported conditions.

Energies and molecular properties of species along the PES were calculated at the G3 level of theory and the results used to calculate the rate constant. Frequencies and rotational constants of the major stationary points along the PES are reported.

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Rate constant values calculated from the Arrhenius expression:

T (K)k(T) [cm3/molecule s]
700 8.99E-12
800 8.74E-12
900 8.53E-12
1000 8.35E-12
1100 8.18E-12
1200 8.04E-12
1300 7.90E-12
1400 7.78E-12
1500 7.67E-12
1600 7.57E-12
1700 7.48E-12
1800 7.39E-12
1900 7.31E-12
2000 7.23E-12