Kinetics and mechanism of the reaction of CH3O with NO

Abstract

AbstractThe kinetics of the reaction of CH3O with NO and the branching ratio for HCHO product formation, obtained as ΓHCHO = (Rate of HCHO formation) / (Rate of CH3O decay), have been studied using a discharge flow reactor. Laser induced fluorescence has been used to monitor the decay of the CH3O radical and the build‐up of the HCHO product. Overall rate constants and product branching ratios were measured at room temperature over the pressure range of 0.72–8.5 torr He. Three reaction mechanisms were considered which differed in the routes of HCHO formation: (i) direct disproportionation; (ii) via an energized collision complex; or (iii) both reaction routes. It has been shown that data on the pressure dependence of the overall rate constant are not sufficient to distinguish between these mechanisms. In addition, an accurate value of Γ is required. Analysis of the available experimental data provided 0.0 and about 0.1 as the lower and upper limit for Γ, respectively. Since the rate constants derived for CH3ONO formation were not sensitive to the value assumed for Γ, k = (1.69 ± 0.69) × 10−29 cm6 molecule−2 s−1 and k = (2.45 ± 0.31) × 10−11 cm3 molecule−1 s−1 could be derived. The rate constant obtained for formaldehyde formation when extrapolated to zero pressure is k = (3.15 ± 0.92) × 10−12 cm3 molecule−1 s−1. © 1994 John Wiley & Sons, Inc.