Abstract
The relative rates of the two competing isotopic reactions: F + CH2D2 → HF + CHD2 and F + CH2D2 → DF + CH2D, were measured in a fast flow system by direct mass spectrometric analysis of the reaction products in the temperature range of 159° to 298°K. The ratio of rates can be expressed as an Arrhenius type equation: kF+HCHD2/kF+DCH2D = (0.81 ± 0.03) exp[(275 ± 15)/R T]. The relation between the intramolecular isotope effect kF+HCHD2/kF+DCH2D and the intermolecular isotope effect kF+CH4/kF+CD4 is discussed with regard to secondary isotope effects in the fluorine atom + methane reaction.