Kinetics of the Reactions between CH₂(X³B₁)‐Radicals and Saturated Hydrocarbons in the Temperature Range 296 K ≤ T ≤ 707 K

Abstract

Abstract The reaction between CH 2 ‐radicals in their ground electronic state (X̃ 3 B 1 ) and n‐hexane equation image was studied in a discharge flow system with LMR detection of CH 2 . In the temperature regime 413 K ≤ T ≤ 707 K the experimental rate constant was found to be equation image The reaction proceeds both via direct H‐atom abstraction by CH 2 (X̃) and via thermal excitation of CH 2 (X̃) to the low‐lying singlet state (ã 1 A 1 ) followed by fast consecutive reactions of CH 2 (ã). The contributions due to thermal excitation and singlet reaction were evaluated for the present work as well as for a recent study of the reactions of CH 2 (X̃) with a series of other hydrocarbons. Corrected rate constants k T for the direct reactions of CH 2 (X̃) with the reactants HR = CH 4 (1), C 2 H 6 (2), C 3 H 8 (3), n‐C 6 H 14 (4), i‐C 4 H 10 (5), and CH 3 CHO (6) in the temperature range 296 K ≤ T ≤ 707 K were found to be equation image The activation energies for the reactions studied are described by an Evans Polanyi type relation. Arrhenius expressions are proposed for the rate constants of H‐atom abstraction by CH 2 (X̃ 3 B 1 ) from primary, secondary, tertiary, and aldehydic C ‐H bonds. The results are compared to the isoelectronic reactions of O( 3 P).