Reactions involving fluoride ion. Part 34. Stable perfluorinated carbanions

Abstract

A remarkable series of perfluoroalkyl anions, generated by reaction of caesium fluoride with various perfluorinated alkenes have been observed by ¹⁹F and ¹³C n.m.r. spectroscopy. Trapping experiments are described and threshold temperatures are established for the onset of fluoride ion exchange. The effects of counter ions are compared and (Me₂N)₃S⁺(TAS) salts are more readily produced than Cs⁺ salts, but exchange of fluoride ion with fluorinated alkenes occurs more readily with TAS salts. Ph₄P⁺ and Bu₄N⁺ salts could not be obtained. Competition experiments for CsF between various perfluoroalkenes has established orders of carbanion stability.