Tetra-alkylammonium fluorides and chlorides in glacial acetic acid solution: nuclear magnetic resonance studies, deuterium fractionation factors (φ), and anion hydrogen bonding

Abstract

The salts NMe₄F, NEt₄F, and NBuⁿ₄F dissolve very readily in MeCO₂H and cause downfield shifts of the acid proton that are linearly related to the fluoride concentration. From these measurements and those in MeCO₂D the fractionation factors (φ) have been calculated and give an average value of 0.55, indicative of anion solvation involving strong hydrogen bonding. The corresponding tetraalkylammonium chlorides produce upfield chemical shifts and average φ of 1.26, which indicates much weaker anion solvation.