Electron attachment to halogenated alkenes and alkanes, 300-600 K

Rate coefficients (k$_{a})$ and ion product distributions have been measured for 14 alkenes and alkanes with bromine, fluorine, and iodine substituents over the temperature range T = 300-600 K using a flowing-afterglow Langmuir-probe apparatus (FALP), most for the first time. Among these are 3 isomers of C$_{3}$F$_{5}$Br and 2 isomers of C$_{3}$F$_{7}$I. Four dibromide compounds yield Br$_{2}^{-}$ in addition to Br$^{-}$. The results follow the expected trends: k$_{a}$ values near the capture limit decrease slightly with T according to Vogt-Wannier theory, while k$_{a}$ increase with T for molecules which have small k$_{a}$ at 300 K. The results are analyzed using a statistical kinetic modeling approach, which is able to reproduce k$_{a}$ values and product branching within experimental uncertainty. The modeling indicates that factor of 2 differences in k$_{a}$ for the isomeric species can be explained by subtle variations in the potential surfaces.