THERMAL-DECOMPOSITION OF VINYLACETYLENE IN SHOCK-WAVES

The thermal decomposition of vinylacetylene (C4H4) was studied behind reflected shock waves using both a single-pulse method (reaction time between 0.8 and 3.3 ms) and a time-resolved UV-absorption method (230 nm). The studies were done over the temperature range of 1170-1690 K at the total pressure range of 1.3-2.3 atm. The mechanism was used to interpret both the early and late stages of vinylacetylene decomposition at the high temperatures. It was confirmed that C4H4 dissociation proceeded through the following three channels. (1) C4H4 --> i-C4H3 + H (2) C4H4 --> C2H2 + C2H2 (3) C4H4 --> C4H2 + H-2 The rate constant expression of reaction (1) was determined as k1 = 6.3 X 10(13) exp(-87.1 kcal/RT) s-1. The rate constants of the succeeding reactions (chain reaction, C4H4 + H --> i-C4H3 + H-2 and C4H4 + H --> C2H2 + C2H3 and decomposition reactions of free radicals, i-C4H3 + M --> C4H2 + H + M) were confirmed or estimated.