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- Title
Origin of Salt Effects in S N 2 Fluorination Using KF Promoted by Ionic Liquids: Quantum Chemical Analysis.
- Authors
Oh, Young-Ho; Lee, Sungyul
- Abstract
Quantum chemical analysis is presented, motivated by Grée and co-workers' observation of salt effects [Adv. Synth. Catal. 2006, 348, 1149–1153] for SN2 fluorination of KF in ionic liquids (ILs). We examine the relative promoting capacity of KF in [bmim]PF6 vs. [bmim]Cl by comparing the activation barriers of the reaction in the two ILs. We also elucidate the origin of the experimentally observed additional rate acceleration in IL [bmim]PF6 achieved by adding KPF6. We find that the anion PF6− in the added salt acts as an extra Lewis base binding to the counter-cation K+ to alleviate the strong Coulomb attractive force on the nucleophile F−, decreasing the Gibbs free energy of activation as compared with that in its absence, which is in good agreement with experimental observations of rate enhancement. We also predict that using 2 eq. KF together with an eq. KPF6 would further activate SN2 fluorination
- Subjects
QUANTUM liquids; ANALYTICAL chemistry; IONIC liquids; FLUORINATION; GIBBS' free energy
- Publication
Molecules, 2021, Vol 26, Issue 19, p5738
- ISSN
1420-3049
- Publication type
Article
- DOI
10.3390/molecules26195738