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

The reaction between CH2‐radicals in their ground electronic state (X̃3B1) and n‐hexane equation image was studied in a discharge flow system with LMR detection of CH2. 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 CH2(X̃) and via thermal excitation of CH2(X̃) to the low‐lying singlet state (ã1A1) followed by fast consecutive reactions of CH2(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 CH2(X̃) with a series of other hydrocarbons. Corrected rate constants kT for the direct reactions of CH2(X̃) with the reactants HR = CH4 (1), C2H6 (2), C3H8 (3), n‐C6H14 (4), i‐C4H10 (5), and CH3CHO (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 CH2(X̃3B1) from primary, secondary, tertiary, and aldehydic C ‐H bonds. The results are compared to the isoelectronic reactions of O(3P).