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 whereb y radicals are both initiated and terminated by NO (Scheme I). The sch eme accounts for the rate of formation of the main product, vinylacety lene (VA), the lesser products CO and HCN and a very minor product, pr opionitrile. It is also shown to be consistent with other studies belo w 900 K and observation at 300 K on the reactions of vinyl radicals wi th NO. The substantial inhibition of vinyl acetylene formation by 5% N O makes untenable any substantial role of vinylidene in the C2H2 pyrol ysis above 1000 degrees K. The reaction of NO with acetylene is an eff icient source of HCN. It appears to be a general reaction of NO with s ubstituted acetylenes and below 900 K a mechanism is presented to acco unt for the production of acrylonitrile (AN) from the reaction of NO w ith VA. Thermochemical data are estimated on Delta(f)H degrees(298) an d S degrees(298) for some alkyl-NO, vinyl NO, and acetylene NO compoun ds and radicals and some new and some revised group values are estimat ed for estimating Delta(f)H degrees(298) of derivatives of hydroxyl am ines, imines, and isoxazolines. (C) 1994 John Wiley & Sons, Inc.