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Mechanism of Nucleophilic Fluorination Facilitated by a Pyrene‐tagged Ionic Liquids: Synergistic Effects of Pyrene–Metal Cation π‐Interactions
Author(s) -
Min Byeong Ki,
Lee SungSik,
Kang Seok Min,
Kim Jiyeon,
Kim Dong Wook,
Lee Sungyul
Publication year - 2018
Publication title -
bulletin of the korean chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.237
H-Index - 59
ISSN - 1229-5949
DOI - 10.1002/bkcs.11548
Subject(s) - ionic liquid , pyrene , chemistry , gibbs free energy , nucleophile , metal , ion , solvent , inorganic chemistry , medicinal chemistry , organic chemistry , catalysis , thermodynamics , physics
We examine the mechanism of S N 2 fluorination promoted by a pyrene‐tagged ionic liquid (PIL). Comparison is made for contact ion‐pair (CIP) vs. solvent‐separated ion‐pair (SSIP) mechanism by calculating the Gibbs free energies of pre‐reaction complexes and Gibbs free energies of activation G ‡ for both processes. We find that the CIP mechanism is preferred for [PIL + MF + C 3 H 7 OMs] (M = Cs, K) system. S N 2 fluorination of the [1‐Butyl‐3‐methylimidazolium (bmim)‐CsF] system is also studied in order to estimate the efficacy of PIL vs. more conventional ionic liquid [bmim][OMs]. The better promotion of the reaction by PIL is attributed to π interactions between the metal cation and pyrene, giving G ‡ that is smaller (by approximately 1.3 kcal/mol) than that for the [bmim‐CsF] system, in excellent agreement with experimental observations.