It was found that the reaction of mesomeric fluorocarbanions of the CF 3 XCOY type with benzoic anhydride leads to the loss of benzoyl fluoride and the formation of mesomeric carbanions of the FCO XCOY type. In a similar reaction with perfluorocarboxylic acid anhydrides, besides a CF 3 →COF transformation, further change of COF into COR F is observed, leading to the formation of salts containing mesomeric anions of the R F CO XCOY type, which, upon acidification, ...