Hydrogen Bonding in S_N2 Reactions Promoted or Inhibited by Ionic Liquids: Effects of Side Chain

Abstract

Quantum chemical analysis is presented for the origin of promotion and inhibition of SN2 fluorination by [bmim][PF6](1) and [hexaEGmim][PF6](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 SN2 fluorination by positioning the nucleophile F− far off the electropositive C atom in prereaction complex. On the other hand, in SN2 fluorination under the influence of [bmim][PF6], the nucleophile F− is in proximity to the electropositive C for facile nucleophilic attack by F−. Comparisons are made for SN2 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.

Novel electrodes and gate dielectrics for field‐effect transistors based on two‐dimensional materials

“…The ions inside an IL are mobile, so they can be drifted by an external electrical field. ILs have been widely used in synthesis, catalysis, electrochemistry, and medicinal chemistry 71–73 . And recently, they have been implemented for gate dielectrics 74,75 .…”

“…ILs have been widely used in synthesis, catalysis, electrochemistry, and medicinal chemistry. [71][72][73] And recently, they have been implemented for gate dielectrics. 74,75 Their capacitance is extremely large due to the electrical double layer (EDL).…”

Ionic Liquids as Organocatalysts for Nucleophilic Fluorination: Concepts and Perspectives

“…Once the role of ILs as amphiphilic “electrophile-nucleophile” dual activators, and specifically the action of the IL anion as a Lewis base interacting with the alkali metal counter-cation, was elucidated, then the scheme for further development would be systematic and straightforward. Several investigators indeed carried out this task [ 34 , 47 , 48 , 49 , 50 ].…”

Enhancement of SNAr reactions by CH3SO3− ionic liquid and organic solvent dimethylformamide as bifunctional organocatalysts: A mechanistic study

“…Besides their extremely useful properties as solvent, ionic liquids (ILs) [1][2][3][4][5][6][7][8][9][10][11] are now considered to be highly efficient tool for enhancing the rates of chemical reactions. [12][13][14][15][16][17][18][19][20][21][22][23] The ionic nature of the IL anion and cation seems to be the origin of this fascinating function of ILs as organocatalyst/promoter through their strong electrostatic (Coulombic) forces on other ionic species in the reaction and also through the formation of hydrogen bonds with various functional groups in substrates. It is now possible to tailor-make ILs for specific purposes as solvent/promoters in a variety of situations by carefully monitoring these interactions.…”