Quaternary ammonium hydrogen difluorides

Quaternary ammonium hydrogen difluorides and dihydrogen trifluorides... 

Quaternary ammonium hydrogen difluorides KHF2 (7.8 g, O.l mol) is added to the quaternary ammonium hydrogen sulphate (O.l mol), neutralized with KHCOj (10 g), in CHClj (500 ml) and H20 (25 ml) and the mixture is stirred at room temperature for ca. 

I h. The organic phase is separated and evaporated to yield the quaternary ammonium hydrogen difluoride. Any dihydrogen trifluoride salt formed at the same time can be removed by dissolution of the product in MeCN and neutralization with anhydrous... 

The ability of quaternary ammonium halides to form weakly H-bonded complex ion-pairs with acids is well established, as illustrated by the stability of quaternary ammonium hydrogen difluoride and dihydrogen trifluorides [e.g. 60] and the extractability of halogen acids [61]. It has also been shown that weaker acids, such as hypochlorous acid, carboxylic acids, phenols, alcohols and hydrogen peroxide [61-64] also form complex ion-pairs. Such ion-pairs can often be beneficial in phase-transfer reactions, but the lipophilic nature of H-bonded complex ion-pairs with oxy acids, e.g. [Q+X HOAr] or [Q+X HO.CO.R], inhibits O-alkylation reactions necessitating the maintenance of the aqueous phase at pH > 7.0 with sodium or potassium carbonate to ensure effective formation of ethers or esterification [49,64]. 

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