The nucleophilic displacement (SN2) reaction F− + CH3Cl→CH3F + Cl− induced by resonant electron capture in gas phase clusters

Abstract

It is shown that the title nucleophilic displacement reaction can be observed in a crossed beam experiment where binary clusters composed of NF₃ and CH₃Cl interact with a monochromatized electron beam. The nucleophile, F⁻ is generated within an energy region around 2 eV by resonant dissociative electron attachment (DA) from the NF₃ component of the cluster and then undergoes an S_N2 reaction with the ‘‘substrate ’’ molecule CH₃Cl. While low energy electron impact to CH₃Cl gives no measurable Cl⁻ signal due to the extremely low DA cross section (<10⁻²² cm²), we observe copious amounts of Cl⁻ ions from the mixed cluster ions carrying the DA resonance profile of F⁻/NF₃ which are hence identified as products of the corresponding S_N2 reaction.