DISPLACEMENT REACTION DYNAMICS OF FLUORINE-ATOMS WITH VINYL BROMIDE MOLECULES

Reactive scattering of F atoms with C2H3Br molecules leading to both H and Pr atom displacement has been studied at an initial translational energy E similar to 40 kJ mol(-1) using a supersonic beam of F atoms seeded in He buffer gas. The center-of-mass angular distribution of C2 H3F reactive scattering shows a sharp forward peak with a lower backwa rd peak of relative intensity similar to 0.5. The product translationa l energy distribution peaks at a low fraction f'(pk) similar to 0.1 of the total available energy with a tail extending up to higher energy. The branching ratio similar to 10 strongly favors Br atom displacemen t over H atom displacement. The H atom displacement pathway occurs in competition with F atom migration in the FCH2CHBr. radical formed by F atom addition to the C=C double bond. The Pr atom displacement occurs in the .CH2CHBrF radical formed either by F atom migration from FCH2C HBr. or directly from F atom addition to the C=C double bond. In eithe r case, Br atom displacement occurs rapidly compared with the rate of F atom migration over the potential energy barrier in the bridged conf iguration, resulting overall in a short-lived collision complex mechan ism for the formation of C2H3F reaction products.