Shock wave studies by mass spectrometry. II. Polymerization and oxidation of acetylene

Abstract

The polymerization and oxidation of acetylene have been investigated at temperatures from 1800°2700°K and 950°-1100°K, respectively, by the technique of time-of-flight mass spectrometry in reflected shock waves. In the absence of oxygen, a simple bimolecular reaction produces a dimer, probably vinylacetylene, and higher polymers, which appear to reach "equilibrium" with the acetylene. A sharp drop in the concentration of these polymers is observed at a later time, which is correlated with the formation of carbon after an induction period. In the presence of oxygen, a dimer, probably diacetylene, is formed simultaneously with the formation of CO and H2O, after an induction period. This suggests that it is a product of the branching chain reaction, a specific mechanism for which is proposed.