The Trifluoroacetic Acid Solvent System. Part II. Acids

Abstract

19F nuclear magnetic resonance (n.m.r.) studies show that SbF5 forms HSbF,(OOCCF,) in trifluoroacetic acid. This complex acid does not react with (CF3CO)20 which must be added to carry out conductimetric studies in anhydrous HOOCCF3. However, HCIO.,, HS03F, and HNO, all react with (CF3CO)Z0 to yield mixed anhydrides CF3COC104, CF3COS03F, and N0200CCF3. HBF., reacts with the anhydride to give CF3COF while HZS04 appears to be simply dehydrated to polysulfuric acids.

Complex fluoroanions in solution. VII. Replacement of fluoride by trifluoroacetate

“…Only three fully substituted anionic species, B(TFA),:, Ge(TFA), '-, and T~(TFA),'-, where T F A is trifluoroacetate, have been reported (1). The only mixed species containing both fluoride and T F A radicals found thus far are HSbF,TFA and perhaps (SbF,),TFA- (2). Fluoroanions frequently form fluorine bridged complex fluoroanions with binary fluorides (3).…”

The Trifluoroacetic Acid Solvent System. Part III. The Acid, HB(OOCCF3)4, and the Solvent Autoprotolysis Constant

“…This procedure was followed without disconnecting the As a base trifluoroacetic acid is very weak, 'being a non-electrolyte in 100% sulfuric acid (4). Several studies of acids in pure trifluoroacetic acid have been made (5-7) but the hygroscopic nature of the solvent and the low concentrations of solute that must be studied to avoid complication from higher ion aggregates (< lo-, M ) make such studies difficult (7). Any water present in the solvent will react with an acid solute, HA, to give H,O+A-which will produce spurious results.…”

“…To avoid interference from water, trifluoroacetic acid anhydride may be added in small amounts (-0.5%) without seriously affecting the dielectic constant and viscosity sf the solvent. However, the anhydride is found to react with many of the common strong acids (7). Two acids which may be studied in the presence of anhydride are HSbF,-(OOCGF,) (7) and NB(OOCCF,),.…”