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Author(s):   Galland, N.; Caralp, F.; Hannachi, Y.; Bergeat, A.; Loison, J.-C.
Title:   Experimental and Theoretical Studies of the Methylidyne CH(X2Π) Radical Reaction with Ethane (C2H6): Overall Rate Constant and Product Channels
Journal:   J. Phys. Chem. A
Volume:   107
Page(s):   5419 - 5426
Year:   2003
Reference type:   Journal article
Squib:   2003GAL/CAR5419-5426

Reaction:   C2H6 + ·CHn-C3H7
Reaction order:   2
Rate expression:   no rate data available
Category:  Theory
Data type:   Ab initio
Comments:   Combined experimental and ab initio study. Typical pressure 1.5 torr He(?). C2H6 partial pressure 0 to 3E13 cm-3 (1 mtorr), est. CH 0.003 mtorr. Temperature 298 K. CH produced by reaction of K with CHBr3 -> CH + 3KBr (3 steps), overall -393 kJ/mol exothermic. CH detected using LIF at 431 nm. H atom product detected with VUV resonance fluorescence in order to get branching ratio of
C2H6 + CH -> C2H4 + CH3 and C2H6 + CH -> Propene + H
Reaction pathway is
C2H6 + CH -> n-Propyl
n-Propyl -> iso-Propyl
n-Propyl -> C2H4 + CH3 or Propene + H
iso-Propyl -> C2H4 + CH3
Total rate constant and branching ratio in agreement with RRKM predictions and other experimental measurements such as for n-Propyl and iso-Propyl decomposition.

Calculated barriers of 160 kJ/mol for n-Propyl to iso-Propyl isomerization, 129 kJ/mol for n-Propyl -> C2H4 + CH3, 151 kJ/ml for n-Propyl -> Propene + H, and147 kJ/mol for iso-Propyl -> Propene + H. Also calculated large barrier of 242 kJ/mol for n-Propyl -> Cyclopropane + H.

Ab initio calculations were done using B3LYP/aug-cc-pVDZ geometries and computing CCSD(T)/cc-pVTZ energies.

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