Anhydrous hydrogen fluoride, room-temperature

Initially, the cyclization reaction of 2-benzylpent-4-enoic acid 4 was carried out using concentrated sulfuric acid as both the catalyst and the solvent at a temperature below 45 °C. Further, the repetoire of Bronsted acids (used at ambient or higher temperature) has been expanded to include anhydrous hydrogen fluoride (0 °C)," trifluoroacetic acid (toluene, 70 °C or acetic acid, 70 °C), polyphosphoric acid (xylenes, reflux),and anhydrous pyridinium poly(hydrogen fluoride) (room temperature). 

Titanium trifluoride is prepared by dissolving titanium metal in hydrofluoric acid (1,2) or by passing anhydrous hydrogen fluoride over titanium trihydrate at 700°C or over heated titanium powder (3). Reaction of titanium trichloride and anhydrous hydrogen fluoride at room temperature yields a cmde product that can be purified by sublimation under high vacuum at 930—950°C. 

Tungsten tetrafluofide [13766-47-7] WF, is a nonvolatile, hygroscopic, reddish-brown soHd. It has been prepared in low yields by the reduction of the hexafluoride with phosphoms trifluofide in the presence of Hquid anhydrous hydrogen fluoride at room temperature (6). 

Fluorodehydroxylations of secondary and tertiary alcohols can be carried out very favorably at — 70 C up to + 50 C (0.5-3 h), when 70% hydrogen fluoride/pyridine (Table 17) or 86% hydrogen fluoride/melamine are used instead of anhydrous hydrogen fluoride itself.11 -31 -ii.266 Secondary alcohols react with 50- 70 % hydrogen fluoride/pyridine, frequently at room temperature. 

Potassium fluoride-poly(hydrogen fluoride) salts are useful fluorine sources for bromo- and iodofluorinations of various alkenes (Method F).49 The best yields arc obtained with KH3F4 and KH4F5. The salts are prepared by mixing the calculated amounts of potassium hydrogen difluoride and anhydrous hydrogen fluoride in a reaction vessel made of polyethylene or Hastel-loy B. The mixture is stirred and heated at 60-70 C to form a homogeneous solution of the salt which solidifies at room temperature. 

A convenient method for the chlorofluorination of cyclohexene, with a mixture of lead(IV) acetate and anhydrous hydrogen fluoride in the presence of sodium or copper(II) chloride in 1,1,2-trichlorotrifluoroethane (Halon-113) at room temperature, has been described.22 The major product in this reaction is /ranj-l-chloro-2-fluorocyclohexane obtained in 70% yield. Byproducts are 2-chlorocyclohexanol and l-acetoxy-2-chlorocyclohexane which are obtained in 25 and 5 % yield, respectively. 

Treatment 2,3-dichloro-5-(trichloromethyl)pyridine in anhydrous hydrogen fluoride with mercury(II) oxide (red) at room temperature for 22 hours provides 2,3-dichloro-5-(tri-fluoromethyl)pyridine in 98% yield.59... 

Potassium hexafluoronickelate(IV), rhombohedral nickel(III) fluoride, and nickel(lV) fluoride are exceedingly powerful fluorinating agents, more powerful than cobalt(III) fluoride. In solution or suspension in anhydrous hydrogen fluoride at room temperature, they will convert58 the cyclohexyl compound 22 into 23 (R —NiF, or NiF4) and 24 (K2NiF6). 

Strfvents for Radical/C don Salts. All of the perfluoro aromatic cation salts are readily soluble in anhydrous hydrogen fluoride, antimony, and iodine pentafluorides and in dry sulfur dioxide. The marked dependency of solubility in HF on temperature provided for the formation of crystals useful for single-crystal X-ray diffraction studies in the case of C FgAsP. The freshly prepared salt was dissolved in anhydrous HF at room temperature and the solution cooled slowly 10 195 K, when amber-colored... 

When metallic gold is exposed to elemental fluorine (F2) at room temperature in the presence of the ionizing solvent liquid anhydrous hydrogen fluoride (aHF) containing an alkali fluoride, the metal is quickly dissolved to give the alkali salt of the anion... 

The room temperature oxidation of gold, ruthenium, osmium, iridium, platinum, or palladium with fluorine in anhydrous hydrogen fluoride... 

G. Lucier, S. H. Elder, L. Chacon and N. Bartlett, The Room Temperature Oxidation of Gold, Ruthenium, Osmium, Iridium, Platinum, or Palladium with Fluorine in Anhydrous Hydrogen Fluoride, European J. Solid State Inorg. Chem. 33 (1996) 809-820. 

Anhydrous hydrogen fluoride is much more effective and cleaves all three groups at room temperature in an autoclave. Alternatively, trialkylboranes are readily protonolyzed by carboxylic acids. Two alkyl groups are removed from many trialkylboranes by treatment with excess of an anhydrous carboxylic acid at room temperature, and the third is removed on heating. Typically, the trialkylborane is refluxed for 2-3 h with propanoic acid in diglyme to effect complete conversion (equation 55). The method is considered in greater detail in Section 3.10.7.2. Alternatively, 2,2-dimethylpropanoic acid can be used to catalyze the reaction with water or other protic species. 2 76... 

Prepared by reaction of diketene with anhydrous hydrogen fluoride, the reagent can be stored for weeks at 0°, but at room temperature it slowly decomposes to form... 

Thiazyl trifluoride (63.8 g 0.619 mol), carbonyl fluoride (51.0 g 0.772 mol) and anhydrous hydrogen fluoride (12.6 g 0.630 mol) are measured out by PVT (pressure, volume, temperature) methods and condensed into a 300-mL stainless steel Hoke cylinder [ISOOpsig (pounds per square inch, gauge)] attached to a stainless steel vacuum line. The cylinder is allowed to warm to room temperature. Then it is placed in a rocker and allowed to shake. 

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