Salt alkali fluoride

The matrix codeposition of CsF with HF (31,32) in an excess of argon, up to Ar/HF ratios of 3000, yielded intense bands at 1364 and 1218 cm, within a few wavenumbers of the HF2 band positions in ionic lattices 29]. The deuterium shift, upon formation of DF2, was slightly above the harmonic value of 1.41, indicating that the anion maintained a center of symmetry. Similar results were obtained with other alkali fluoride salts, but the product yield decreased as the radius of the alkali metal cation decreased. These results provided immediate confirmation of the salt/molecule technique, demonstrating that for a known system ion pair formation occurred and that the spectrum of the product anion resembled closely that of the anion in known environments. 

An alternative view of the interaction of an alkali metal cation with a fluoride-containing anion is one of Lewis acid/base competition. The reactions discussed in the preceding section involved the reaction of an alkali fluoride salt with a Lewis acid with subsequent fluoride ion transfer to the Lewis acid. However, the alkali metal cation is a Lewis acid as well, and the degree of perturbation of the anion by the cation may be dependent on the differences in fluoride ion affinity of the Lewis acid and the alkali metal cation. The fluoride ion affinities for a variety of Lewis acids are well known from ICR (53,54,64) studies, while the fluoride ion affinities for alkali metal cations are the heterolytic bond dissociation energies of the gas phase alkali fluoride molecules... 

Fluorides represent another alternative to oxides, and may have higher redox potentials compared with similar oxides [54]. In comparison with the alkali fluoride salts used in the preparation of vanadium phosphates [62,63], Kohl et al. [54] prepared lithiated transition metal fluorides, LigMFg, using acetyl acet-onate salts as metal precursors and organic solutions of HF as a fluoride source. Extensive structural characterizations were presented for M = V, Mn, Cr, and Fe and the crystalline domain size was found to vary between 30 and 200 nm. However, no electrochemical characterization was reported. 

There are some means for synthesis of defined primary or secondary esters. Monoester salts of phosphoric acid, for instance, are prepared by addition of alcohol or ethoxylated alcohol, alkali fluoride, and pyrophosphoryl chloride (C12P0)20 in a molar ratio of 0.9-1.5 0.05-1 1.0 at -50 to +10°C and hydrolysis of the Cl-containing intermediates with base. Thus, 32.3 g (C12P0)20 was treated at -50°C with 23.9 g lauryl alcohol in the presence of 0.7 g KF and the mixture was slowly warmed to room temperature and hydrolyzed with H20 and 40% NaOH to give 83% sodium monolauryl phosphate. The monoester salts showed comparable or better washing and foaming efficiency than a commercial product [12]. 

Thus removal of water from classical rather inactive fluoride reagents such as tetrabutylammonium fluoride di- or trihydrate by silylation, e.g. in THF, is a prerequisite to the generation of such reactive benzyl, allyl, or trimethylsilyl anions. The complete or partial dehydration of tetrabutylammonium fluoride di- or trihydrate is especially simple in silylation-amination, silylation-cyanation, or analogous reactions in the presence of HMDS 2 or trimethylsilyl cyanide 18, which effect the simultaneous dehydration and activation of the employed hydrated fluoride reagent (cf, also, discussion of the dehydration of such fluoride salts in Section 13.1). For discussion and preparative applications of these and other anhydrous fluoride reagents, for example tetrabutylammonium triphenyldifluorosilicate or Zn(Bp4)2, see Section 12.4. Finally, the volatile trimethylsilyl fluoride 71 (b.p. 17 °C) will react with nucleophiles such as aqueous alkali to give trimethylsilanol 4, HMDSO 7, and alkali fluoride or with alkaline methanol to afford methoxytri-methylsilane 13 a and alkali fluoride. 

An important aspect is that of studying the effects of composition of the efectrolyte solution on the electrocapillary and capacitance curves. Identical curves are obtained for solutions of fluorides, sulfates, and certain other alkali metal salts having identical... 

For the preparation of monofluorophosphates there are quite a lot of methods found in literature. The alkali salts are obtained by shortly melting poly- or trimetaphosphate with alkali fluoride (29,30) - the application of graphite vessels yielding particulary pure products (31) ... 

Eremenko and co-workers used nitryl fluoride for the deamination of amines at subambient temperatures in acetonitrile. The same reaction occurs with primary nitramines and their alkali metal salts bis-nitramines react to give the corresponding bis-nitrate esters. 

Alkyl lV,lV-dinitramines (154) have been prepared from the reaction of the tetraalkylam-monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient temperature. The same reaction with the primary nitramine or its alkali metal salts yields the corresponding nitrate ester. Treatment of the ammonium, potassium, or lithium salts of primary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambient temperature yield alkyl iV,iV-dinitramines. ° The same reactions in ether or ester solvents enables the free nitramine to be used. The nitrolysis of A-alkylnitramides (157) and N,N-diacylamines with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic isocyanates with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl A,A-dinitramines (154). 

The interaction of alkali salts with inorganic and organic acids has been extensively studied by the same group. In the case of alkali fluorides it was shown that milling leads to proton transfer and to formation of KHF2, while the reactivity of fluorides follows the order KF>NH4F>NaF>LiF, Cap2 [71b,c]. 

Reaction with alkali fluorides (except LiF) yields double salts, such as K3[Mo03F3], formed as colorless cubic crystals. 

Rocket propulsion oxidizers, 18 384-385 Rocks, weathering of, radiation and, 3 299 Rocksalt, crystal structure of, 2 6, 29 Rock-salt-type alkali halide crystals, dissolution process, 39 411 19 alkali chlorides, 39 413, 416 alkali fluorides, 39 413-415... 

The enhanced nucleophilicity of weakly solvated fluoride ions, solubilized in non-polar solvents as their alkali metal salts by [18]crown-6, has been studied. The wide range of SN2 reactions possible with this system is illustrated in Table 3. Under equivalent conditions in the absence of crown ether no substitution occurs. Similar effects are seen with many nucleophiles which, even if soluble in the solvent employed, show increased nucleophilic substitution rates in the presence of crown ethers (B-78MI52104). However, the monocyclic crown compound exposes the cation on two sides to approach by the counteranion (see Figures lb, c and d for illustrations of this effect in the crystalline state). The resultant ion pairs that form in non-polar solvents reduce the reactivity of the anion. 

Likewise, Bayer AG have patented [ 133] an improvement process which entails the addition of fluoride salts to the HF electrolyte enabling the ECF of alkyl-sulphonyl fluorides to be run for many months, giving high yields and using less energy than usual. Examples of the additives are alkaline earth fluorides, alkali tetrafluoroborates, alkali hexafluorophosphates, HPF6, HBF4 and BF3. 

J. Reich 6 also patented a process based on the calcination of the alkali fluosilicate or fluoborate with an oxide of the alkaline earths. When the calcined mass is lixiviated with water, the alkali fluoride is obtained in soln. L. Schuch 6 made sodium fluoride by boiling finely powdered cryolite with a cone. soln. of sodium hydroxide—the alumina and silica pass into soln.—sodium fluoride crystallizes from the cooling soln. Sodium silicate can be used in place of the hydroxide. F. Jean made sodium fluoride by leaching a calcined mixture of fluorspar, limestone, Glauber s salt, and charcoal. 

Alkali tetrafluoroborates are stable white salts which can easily be prepared starting from boric acid and alkali fluoride in concentrated hydrochloric acid.63... 

An improved procedure for condensation of dithioesters with a-amino groups of amino acids has been used to prepare several peptide thioamidesJ8 The N-protected amino acid dithioesters condense with alkali salts of a-amino acids, catalyzed by alkali fluoride in EtOH, to give the endothiopeptides within 60 minutes. Under these conditions, the thioamides are obtained without racemization. 

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