The influence of fluorination on the dynamics of the F^- + CH₃CH₂I reaction

The competition between the bimolecular nucleophilic substitution (S_N2) and base-induced elimination (E2) reaction and their intrinsic reactivity is of key interest in organic chemistry. To investigate the effect of suppressing the E2 pathway on S_N2 reactivity, we compared the reactions F^- + CH₃CH₂I and F^- + CF₃CH₂I. Differential cross-sections have been measured in a crossed-beam setup combined with velocity map imaging, giving insight into the underlying mechanisms of the individual pathways. Additionally, we employed a selected-ion flow tube to obtain reaction rates and high-level ab initio computations to characterize the different reaction pathways and product channels. The fluorination of the β-carbon not only suppresses the E2-reaction but opens up additional channels involving the abstraction of fluorine. The overall S_N2 reactivity is reduced compared to the non-fluorinated iodoethane. This reduction is presumably due to the competition with the highly reactive channels forming FHF^- and CF₂CI^-.