Ammonium difluoride

Calculate the amount of ammonium difluoride needed to prepare ammonium fluovanadate(III). Take twice as much ammonium difluoride as calculated and melt it in a copper bowl. (Perform the experiment in a fume cupboard, wear eye protection and gloves )... 

SYNS ACID AMMONIUM FLUORIDE AMMONIUM BIFLUORIDE AMMONIUM DIFLUORIDE AMMONIUM FLUORIDE comp, with HYDROGEN FLUORIDE (1 1) AMMONIUM HYDROFLUORIDE AMMONIUM HYDROGEN BIFLUORIDE AMMONIUM HYDROGEN DIFLUORIDE AMMONIUM HYDROGEN FLUORIDE, soUd (UN 1727) (DOT) AMMONIUM HYDROGEN FLUORIDE, solution (UN 2817) (DOT)... 

Fluorosulfonic acid Sodium carbonate Ammonium difluoride... 

Two well-known salts of ammonia (qv) are the normal ammonium fluoride [12125-01 -8] NH F, and ammonium bifluoride [1341 -49-7] NH4HF2 the latter is sometimes named ammonium acid, or hydrogen difluoride. Much of the commercial interest in the ammonium fluorides stems from their chemical reactivity as less ha2ardous substitutes for hydrofluoric acid. 

Electropositive fluorinating agents are categorized in distinct classes as (1) fluoroxy reagents, in which the fluorine is bound to an oxygen atom (for reviews, see references 1,2,3, 4, 5, and 6) (2) fluoraza reagents, in which the fluorine atom IS bound to the nitrogen atom of either an amide or ammonium ion structure (for a partial review, see reference 6), (3) xenon difluoride, in which the fluorine atoms are bound to xenon (for reviews, see references 5, 7, 8, and 114) and (4) perchloryl Iluoride, in which the fluorine atom is bound to the chlorine atom of the perchloryl function (for a review, see reference 9). 

The double fluoride, ammonium hexafluorovanadate ((NH4)3VF6), forms from the oxide at 210 to 250 °C, but decomposes at 600 to 700 °C to yield pure vanadium fluoride. Examples of metal fluorides obtainable through the double fluoride route include uranium tetrafluoride, beryllium difluoride and the rare earth fluorides ... 

Minkwitz, R. et al., Z. Naturforsch. B, Chem. Sci., 1988, 43B, 1478-1480 The impure material is very explosive [1]. The pine material, prepared by a ther-molytic method, is stable as a solid at -103°C, but on melting it decomposes to ammonium hydrogen difluoride and nitrogen [2],... 

Ammonium fluoride, NH4F, Krypton difluoride, KrF2, Sodium chloride, NaCl,... 

In contrast, chemical etching of the inner wall of the fused-silica capillaries was used to increase the surface area. This enables achievement of a higher phase ratio since more alkyl functionalities can be attached to the surface, thus improving both the separation process and loadability of the column. The surface morphology of the etched capillary depends on the time the methanol solution of ammonium hydrogen difluoride is left in contact with the capillary and temperature at which the reaction is carried out (Fig. 10) [77]. The surface features have been described by Pesek to range from spikes of silica material extending... 

Fig. 11A-C. Scanning electron micrographs of fused silica capillary surfaces etched with methanolic ammonium hydrogen difluoride solution. (Reprinted with permission from [78], Copyright 2000 Elsevier). Etching process was carried out for A 3 h at 300 °C B, 2 h at 300 °C and 2 h at 400 °C C 2 h at 300 °C and 1 h at 400 °C...

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]. 

Carbanions, generated by the reaction of benzylsilanes with tetra-n-butylammo-nium fluoride react with non-enolizable aldehydes to produce the alcohol [67], When a stoichiometric amount of the ammonium fluoride is used, the methylarene corresponding to the benzylsilane is frequently a by-product and arises from formation of the hydrogen difluoride salt during the reaction. When only catalytic amounts of the ammonium fluoride initiate the reaction, the formation of the methylarene is suppressed. In a similar type of reaction (although the mechanism is not known) between aldehydes and ketones, allyl bromide, and tin in the presence of trimethylsilyl chloride the yield of the but-l-en-4-ol is raised significantly by the addition of tetra-n-butylammonium bromide, particularly in the reactions with... 

Nitrogen trifluoride is prepared by electrolysis of either molten ammonium fluoride, NH4F, or melted ammonium acid fluoride, NH4HF2 (or ammonium fluoride in anhydrous HF). Whde the NH4F method is preferred because it forms nitrogen trifluoride as the only product, electrolysis of ammonium acid fluoride yields a small amount of dinitrogen difluoride, N2F2, and NF3. 

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