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Hydrogen Bonding in S N 2 Reactions Promoted or Inhibited by Ionic Liquids: Effects of Side Chain
Author(s) -
Oh YoungHo,
Lee Sungyul
Publication year - 2021
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.12214
Subject(s) - nucleophile , ionic liquid , chemistry , hydrogen bond , ionic bonding , hydrogen atom , medicinal chemistry , hydrogen , atom (system on chip) , crystallography , stereochemistry , catalysis , molecule , organic chemistry , ion , group (periodic table) , computer science , embedded system
Quantum chemical analysis is presented for the origin of promotion and inhibition of S N 2 fluorination by [bmim][PF 6 ]( 1 ) and [hexaEGmim][PF 6 ]( 2 ), respectively, experimentally observed by Kim and co‐workers [ Tetrahedron 2014; 70: 533–542]. We show that hydrogen bonding of OH in hexaEGmim + causes complete suppression of S N 2 fluorination by positioning the nucleophile F − far off the electropositive C atom in prereaction complex. On the other hand, in S N 2 fluorination under the influence of [bmim][PF 6 ], the nucleophile F − is in proximity to the electropositive C for facile nucleophilic attack by F − . Comparisons are made for S N 2 fluorination by [hexaEGmim][OMs], which gave the largest rate constant in experiments. The use of ionic interactions and hydrogen bonding for controlling the chemical transformation is illustrated for developing and designing the efficient and task‐specific organocatalysts.