Tetraalkylammonium trifluoromethanesulfonates

Various sources of fluoride ion have been investigated, of which highly nucleophilic tetraalkylammonium fluorides ate the most effective Thuf, fluoro alkyl halides and N (fluoroalkyl)amines are efficiently synthesized by treatment of the corresponding trifluoromethanesulfonic esters with tetrabutylammonium fluoride trihydrate in aprotic solvents [5fl] (equation 34) The displacement reactions proceed quantitatively at room temperature within seconds, but tail with hydrogen fluoride-pyridine and give reasonable yields only with hydrogen fluo ride-alkylamine reagents... 

All these electrolytes are neutral in Bronsted acid-base properties. Although rather exceptional, an acid, a base, or a pH buffer may be added to the supporting electrolyte of neutral salts. The acid-base system to be selected depends on the purpose of the measurement. We often use trifluoromethanesulfonic acid (CF3S03F1) as a strong acid acetic acid, benzoic acid, or phenol as a weak acid an amine or pyridine as a weak base and tetraalkylammonium hydroxide (ILtNOH) as a strong base. Examples of buffer systems are the mixtures of picric acid and its R4N-salt and amines and their PlCl04-salts. Here, we should note that the acid-base reactions in aprotic solvents considerably differ from those in water, as discussed in Chapter 3. 

Tetraalkylammonium tosylates [74] and trifluoromethanesulfonates [72] are also excellent electrolytes. Although tetraalkylammonium ions are favored as the cations for supporting electrolytes because of their wide potential range, other cations are sometimes used for special applications—for example, methyltri-phenyl phosphonium, whose tosylate is freely soluble in methylene chloride, and other fairly nonpolar solvents [74] or metal ions (lithium salts tend to have the best solubility in organic solvents) where undesirable reactions of the tetraalkylammonium ion might occur [13,75]. The properties of many electrolytes suitable for nonaqueous use have been surveyed [76]. 

Trifluoromethanesulfonic acid in the presence of anisole cleaves a number of protecting groups currently used in peptide chemistry without significant side reactions Tetraalkylammonium cyanides, which are soluble in organic solvents, catalyze Michael additions and other base-catalyzed reactions. As nucleophiles they are more powerful than NaCN . 

As we have mentioned above, strongly adsorbed species are needed for good stabilization of nanoparticles. Many ions generally employed in ionic liquids, like the cations tetraalkylammonium (Nk,i,nvn ), tetraalkylphosphonium (Pk.iAnV), and 1,1-dialkyl-pyrrolidinium (CmCnPyr ) and the anions bis(trifluoromethanesulfonyl)amide (Tf2N-), trifluoromethanesulfonate (CF3SO3 ), alkylsulfate (CnOSOs ), tetrafluoroborate (Bp4-), hexa-fluorophosphate (PFe") sue weakly coordinating and, thus, need to be complemented with an appropriate counter ion to stabilize nanopartides efficiently. 

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