Related Experiment Video
Updated: Mar 26, 2026

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition
Published on: May 22, 2015
Influence of the leaving group on the dynamics of a gas-phase SN2 reaction
Martin Stei1, Eduardo Carrascosa1, Martin A Kainz1
1Institute for Ion Physics and Applied Physics, Universität Innsbruck, Technikerstraße 25, Innsbruck 6020, Austria.
Abstract:
In addition to the nucleophile and solvent, the leaving group has a significant influence on SN2 nucleophilic substitution reactions. Its role is frequently discussed with respect to reactivity, but its influence on the reaction dynamics remains unclear. Here, we uncover the influence of the leaving group on the gas-phase dynamics of SN2 reactions in a combined approach of crossed-beam imaging and dynamics simulations. We have studied the reaction F(-) + CH3Cl and compared it to F(-) + CH3I. For the two leaving groups, Cl and I, we find very similar structures and energetics, but the dynamics show qualitatively different features. Simple scaling of the leaving group mass does not explain these differences. Instead, the relevant impact parameters for the reaction mechanisms are found to be crucial and the differences are attributed to the relative orientation of the approaching reactants. This effect occurs on short timescales and may also prevail in solution-phase conditions.
More Related Videos
10:52Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
16:11Thermochemical Studies of NiII and ZnII Ternary Complexes Using Ion Mobility-Mass Spectrometry
Published on: June 8, 2022
Related Concept Videos
SN2 Reaction: Transition State
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
SN2 Reaction: Mechanism
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
Predicting Products: SN1 vs. SN2
With increased substitution on the alkyl halide,...
SN2 Reaction: Stereochemistry
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
Leaving Groups
In general, in a nucleophilic substitution reaction, a nucleophile displaces a functional group, called the leaving group, from the substrate to give a substituted product. A leaving group departs the substrate molecule through heterolytic cleavage, taking the pair of electrons with it to become a relatively stable weak base in the form of an anion or a neutral molecule.
In a...
SN1 Reaction: Mechanism
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a...