Reactions of F2O in Shock Waves. II. Kinetics and Mechanisms of the F2O–CO Reaction

The kinetics of the reaction between oxygen difluoride with carbon monoxide were studies in shock tubes between 800 and 1400°K. Some of the experiments were done with a single pulse tube; these provided data on the production of CO₂, O₂, and F₂CO. In addition time‐resolved optical measurements were made behind incident shock waves. The rate of formation of CO₂ was monitored through its emission at 4.3 μm and, simultaneously, the decrement in F₂O through its absorption at 220 nm, for the reaction $$\mathrm{OF}+\mathrm{CO}\to {\displaystyle {lim}^{k_4}}{\mathrm{CO}}_2+\mathrm{F}.$$ Computer analysis of the experiments yielded $k_4{\text{\hspace{0.17em}=\hspace{0.17em}7.5\hspace{0.17em}×\hspace{0.17em}10}}^{10}{\mathrm{cm}}^3{\mathrm{mole}}^{\text{−1}}·{\sec }^{\text{−1}}$ , independent of temperature. This value is believed to be correct within a factor of 2 between 900 and 1400°K. Combining of our earlier data on the reaction $${\mathrm{F}}_2\mathrm{O}+\mathrm{M}\to {\displaystyle {lim}^{k_1}}\mathrm{F}+\mathrm{OF}+\mathrm{M}$$ with the high‐temperature results from this work and the results from another independent work, we obtain: $k_1{\text{\hspace{0.17em}=\hspace{0.17em}10}}^{\text{16.7}}\text{exp(−40 500\hspace{0.17em}/\hspace{0.17em}RT)}{\mathrm{cm}}^3{\mathrm{mole}}^{\text{−1}}·{\sec }^{\text{−1}}$ from 770 to 1230°K. The error in activation energy is about ±3 kcal/mole. The reaction between F₂O and CO leads to the production of significant amounts of F₂CO, which results in a temperature increase which becomes more important at the lower temperatures. The heating effect, on the basis of the proposed mechanism, was found to be strongly dependent on the concentration of the FCO radical, which is believed to be the intermediate in the formation of F₂CO. The thermochemistry of the FCO radical is discussed. We also very briefly investigated the possibility that Reaction (4) produces vibrationally excited CO₂, with inverted (001)/(100) populations, by measuring the transmitted intensity of 10.6‐μm radiation from a CO₂ laser. No gain was observed, and we concluded that if the initially formed CO₂ is highly vibrationally excited, under the conditions of these experiments the extent of inversion was not sufficient to permit detection with our technique.