Chemical reaction dynamics are studied to monitor and understand the concerted motion of several atoms while they rearrange from reactants to products. When the number of atoms involved increases, the number of pathways, transition states and product channels also increases and rapidly presents a challenge to experiment and theory. Here we disentangle the dynamics of the competition between bimolecular nucleophilic substitution (SN2) and base-induced elimination (E2) in the polyatomic reaction F− + CH3CH2Cl. We find quantitative agreement for the energy- and angle-differential reactive scattering cross-sections between ion-imaging experiments and quasi-classical trajectory simulations on a 21-dimensional potential energy hypersurface. The anti-E2 pathway is most important, but the SN2 pathway becomes more relevant as the collision energy is increased. In both cases the reaction is dominated by direct dynamics. Our study presents atomic-level dynamics of a major benchmark reaction in physical organic chemistry, thereby pushing the number of atoms for detailed reaction dynamics studies to a size that allows applications in many areas of complex chemical networks and environments.
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R.W. thanks the Austrian Science Fund (FWF), project P25956-N20, for support of this work. G.C. thanks the National Research, Development and Innovation Office-NKFIH, K-125317, the Ministry of Human Capacities, Hungary grant 20391-3/2018/FEKUSTRAT and the Momentum (Lendület) Program of the Hungarian Academy of Sciences for financial support. We acknowledge KIFÜ for awarding us access to computational resources based at Debrecen in Hungary. J.M. acknowledges support from a Hertha Firnberg Fellowship of the Austrian Science Fund (T962-N34). E.C. acknowledges support from the DOC Fellowship of the Austrian Academy of Science.
The authors declare no competing interests.
Peer review information Nature Chemistry thanks Piergiorgio Casavecchia, Dunyou Wang and Xingan Wang for their contribution to the peer review of this work.
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Supplementary Materials and Methods, Figs. 1–10.
Source data to support the plots in the Supplementary Information file.
Initial and final QCT coordinates, 0.35 eV.
Initial and final QCT coordinates, 0.83 eV.
Initial and final QCT coordinates, 1.15 eV.
Initial and final QCT coordinates, 1.6 eV.
Initial and final QCT coordinates, 1.98 eV.
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Meyer, J., Tajti, V., Carrascosa, E. et al. Atomistic dynamics of elimination and nucleophilic substitution disentangled for the F− + CH3CH2Cl reaction. Nat. Chem. 13, 977–981 (2021). https://doi.org/10.1038/s41557-021-00753-8