The reaction of hydrogen atoms with propylene

A detailed study has been made of the products of the reaction of hydrogen atoms with propylene. A discharge-flow system at 290 $\pm $ 3 K was used. Total pressures in the range 4 to 16 Torr (550 to 2200 N m$^{-2})$ of argon were used and the flow rates of hydrogen atoms and propylene ranged individually up to about 12 $\mu $mol s$^{-1}$. As found by others the main products are methane, ethane, ethylene, propane and isobutane. Trivial amounts of 2,3-dimethylbutane, but no n-butane, were detected. A detailed mechanism accounting adequately for the reaction is proposed. It is confirmed that formation of the vibrationally excited species, i-C$_{3}$H$_{7}^{\ast}$, is the predominant primary process. Novel processes which are shown to be important are H + i-C$_{3}$H$_{7}^{\ast}\rightarrow $ CH$_{3}$ + C$_{2}$H$_{5}$ and, C$_{3}$H$_{8}^{\ast}\rightarrow $ CH$_{4}$ + C$_{2}$H$_{4}$. A number of rate constant ratios have been evaluated from the data and these allow calculation of absolute rate constants of some individual reactions. The agreement with previously reported values is, in most instances, good.