Acetylene—Oxygen Reaction in Shock Waves. Origin of CO2

Abstract

The ir emissions from CO and CO₂, formed in the C₂H₂–O₂ reaction in a shock tube, have been observed as a function of time. By calibrating these emissions in terms of concentrations and by comparing them with the emission of CH^* (A ²Δ→X ²π), produced in the same reaction, it has been possible to confirm that CO₂ is formed in the early stages by a reaction other than CO+OH→CO₂+H. This reaction involves a primary carbon‐containing radical and an O₂ molecule, and its rate at 1800°K is 5% of the rate of formation of CO, produced by a similar reaction. The importance of the reaction CO+OH→CO₂+H in the later stages of oxidation has been examined as a function of the initial O₂/C₂H₂ ratio, and the growth of OH concentration during the reaction elucidated. More decisive proof is given that CH^* is produced by a reaction which is second order in reaction intermediates.