Kinetics and thermochemistry of the reaction of acetylene and nitric oxide

The shock tube data of Ogura 5] on the pyrolysis of C₂H₂/NO mixtures (1100–1500 K) is shown to be consistent with a simple mechanism whereby radicals are both initiated and terminated by NO (Scheme I). The scheme accounts for the rate of formation of the main product, vinylacetylene (VA), the lesser products CO and HCN and a very minor product, propionitrile. It is also shown to be consistent with other studies below 900 K and observation at 300 K on the reactions of vinyl radicals with NO. The substantial inhibition of vinyl acetylene formation by 5% NO makes untenable any substantial role of vinylidene in the C₂H₂ pyrolysis above 1000°K. The reaction of NO with acetylene is an efficient source of HCN. It appears to be a general reaction of NO with substituted acetylenes and below 900 K a mechanism is presented to account for the production of acrylonitrile (AN) from the reaction of NO with VA. Thermochemical data are estimated on Δ_fH°₂₉₈ and S°₂₉₈ for some alkyl-NO, vinyl NO, and acetylene NO compounds and radicals and some new and some revised group values are estimated for estimating Δ_fH°₂₉₈ of derivatives of hydroxyl amines, imines, and isoxazolines. © 1994 John Wiley & Sons, Inc.