Reaction of Ketene with Atomic Hydrogen and Oxygen

Abstract

The reactions of atomic hydrogen and oxygen with ketene have been studied in a discharge‐flow system coupled to a time‐of‐flight mass spectrometer. The principal products of the H‐atom reaction are CH₄ and CO, and a mechanism consistent with the kinetics of their formation is $$\mathrm{H}\mathrm{\hspace{0.17em}+\hspace{0.17em}}{\mathrm{CH}}_2\mathrm{CO}\mathrm{\hspace{0.17em}=\hspace{0.17em}}{\mathrm{CH}}_3\mathrm{\hspace{0.17em}+\hspace{0.17em}}\mathrm{CO},$$ $${\mathrm{CH}}_3\mathrm{\hspace{0.17em}+\hspace{0.17em}}\mathrm{H}\mathrm{\hspace{0.17em}+\hspace{0.17em}}\mathrm{wall}\mathrm{\hspace{0.17em}=\hspace{0.17em}}{\mathrm{CH}}_4\mathrm{\hspace{0.17em}+\hspace{0.17em}}\mathrm{wall}.$$ The bimolecular rate constant for addition of H to CH₂CO was determined to be: $k_1{\text{\hspace{0.17em}=\hspace{0.17em}1.3\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−13}}{\mathrm{cm}}^3{\mathrm{molecules}}^{\text{−1}}·{\sec }^{\text{−1}}$ at 298°K. The reaction of O atoms with ketene is quite complex. Considerable amounts of CO₂, CO, H₂O, and H₂ are formed, and atomic H and H₂CO were also detected. The data are consistent with an initial addition of O to ketene, $$\mathrm{O}\mathrm{\hspace{0.17em}+\hspace{0.17em}}{\mathrm{CH}}_2\mathrm{CO}\mathrm{\hspace{0.17em}=\hspace{0.17em}}{\mathrm{CH}}_2{\mathrm{CO}}_2,$$ followed by rapid decomposition and the consumption of an additional O atom. The bimolecular rate constant was found to be $k_1{\text{\hspace{0.17em}=\hspace{0.17em}8.8\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−13}}{\mathrm{cm}}^3{\mathrm{molecules}}^{\text{−1}}·{\sec }^{\text{−1}}$ at 298°K.