Determination of pKa values of C-H bonds in polar fluorinated arenes referred to a new CF3SO2-substituted anchor compound.

Abstract

pKa values of C-H bonds remain unreported and challenging in fluorous solvents because of these solvents' unique physicochemical properties, although they have been measured, theorized and predicted successfully in water and common organic solvents. Herein, a new CF3SO2-substituted anchor compound designed for matching the physicochemical properties of polar fluorinated arenes is synthesized. Its self-dissociation constants in these solvents are used as bases for experimentally determining the pKa values of 36 C-H compounds in them. These experimentally determined pKa values exhibit excellent linear free-energy relationships and correlate well with their corresponding DFT-calculated values. These data indicate that the polar fluorinated arenes are thermodynamically more favorable for deprotonation of ketone derivatives than acetonitrile as reaction media, resulting in enhanced deprotonation-promoted CO2 fixation. The pKa values determined in this work can be used as an important guidance tool for reactions involving the formation and cleavage of C-H bonds in polar fluorinated arenes.