Fluoride of Boron

Boron has a remarkable affinity for fluorine, and when fluor spar (fluoride of calcium) is heated to redness with boracic acid, a gaseous compound is produced, analogous in composition and properties to the terchloride of boron. 3 CaF+4 BO,- = 3 (Ca 0, BO,) + BF-j. The sp. g. of the gas is 2 36. It instantly seizes on water, decomposing it, and thus, like the chloride, forms very thick vapours wifli the moisture of the air. It is, in fact, a very delicate test of the presence of moisture in any gas. 

When this gas is absorbed by water to saturation, hydrofluoric acid and boracic acid are formed BF, + 3HO=3HF + BO,. The hydrofluoric acid unites with the boracic acid and 1 eq. of water forming an acid, 3 HF + HO, BO, and this, when acted on by bases, yields salts, the formula of which is 3MF +MO,BO,. Berzeliushas shown that when terfluoride of boron is absorbed by concentrated hydrofluoric acid, another colnpound is formed, the formula of which is HF + BF,. It is an acid, the formula of its salts being MF + BF,. All its salts, when heated, give off terfluoride of boron. 

when heated in the vapour of sulphur, bums and forms a sulphuret of boron, which is a white solid decomposed by water, with which it yields sulphuretted hydrogen and boracic acid. 

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Cyanogen fluoride is a moderately endothermic compound, with AHyfg) +35.8 kJ/ mol, or 0.79 kJ/g. Polymerisation of cyanogen fluoride is rapid at ambient temperature and explosive in presence of hydrogen fluoride [1], Cyanogen fluoride develops more pressure than would acetylene when initiated in the liquid phase at —41 °C by a squib. At —80°C either hydrogen fluoride of boron trifluoride may initiate violent decomposition. The pure vapour is insensitive to sparks or igniters, but mixtures with air are more powerful than those of acetylene [2],... 

A. The Oxide Fluorides of Boron, Aluminium, Gallium, Indium, and Thallium... 

For less activated aromatic systems (those without a nitro substituent), the halogcn-ex-changc reaction has been investigated with potassium fluoride in a variety of polar aprotic solvents in the presence or absence of a catalyst (see Table 13). Many different types of catalysts have been investigated these include crown ethers, quaternary ammonium salts, 3,164 pjjos-phonium salts, aminophosphonium salts, compounds containing a phosphorus and an amino function, and inorganic fluorides of boron, aluminum, tin, phosphorus, titanium and zirconium. Different forms of potassium fluoride have been used these include spray-dried potassium fluoride, freeze-dried potassium fluoride, potassium fluoride recryslal-lized from methanol, and potassium fluoride dispersed on caleium fluoride. ... 

Boron forms strong bonds to fluorine (644kJmol ), usually combining with three or four fluorides in its compounds or salts. Several binary fluorides of boron are known including boron trifluoride, BF3, a stable gas of great industrial importance as a Lewis acid. Boron trifluoride is synthesized industrially by reaction of hydrofluoric acid with borates or boric oxides (equation 42). ... 

Reaction of BF3 with B at 1850 °C generates the reactive intermediate species boron monofluoride, BF, which cannot be isolated. Cocondensation of BF with BF3 yields B2F4, a metastable lower fluoride of boron, and BF2-B(F) BF2, which is unstable and disproportionates according to equation (46). Mixtures of boron trihalides undergo exchange reactions, presumably via a four-centered... 

Other acids in bromine(III) fluoride are the fluorides of boron, gold(III), silicon, germanium, tin(IV), titanium(IV), phosphorus(V), arsenic(V), bismuth(V), vana-dium(V), niobium(V), tantalum(V), ruthenium(V), platinum(V) as well as hydrogen fluoride and sulphur trioxide ... 

When fluoride of boron is brought in contaidi with water, boric and llnoborio acids remain in solution thus —... 

BrF and CIF ) and fused meteillle fluorides. Host elements form fluorides under the conditions that UFg Is obtained. However, only a small number of these fluorides are volatile. Hyman, et al. have published a table of some 26 elements having fluorides with boiling or sublimation points of 550 C or less. Included In this group are the fluorides of boron, silicon, phosphorus, vanadium, sulfur, tungsten, bismuth, plutonium, and the fission products, germanium, arsenic, selenium, niobium, molybdenum, ruthenium, antimony, tellurium, and Iodine. The boiling point of UFg Is 5lf.6 C. Non-volatlle fluorides from which uranium Is readily separated Include those of the alkali metals, alkaline earths, rare earths, Fe, Co, Nl, Ag, Al, Bg, )ta, Tl, Fb, Zn, Cu,... 

A pair of isoelectronic species for C and N exist with the formula X2O4 in which there is an X—X bond. A corresponding fluoride of boron also exists. Draw Lewis structures for these species and describe their shapes. 

Another aspect of my early research in Budapest was in nitration chemistry, specifically the preparation of nitronium tetrafluoroborate, a stable nitronium salt. 1 was able to prepare the salt in a simple and efficient way from nitric acid, hydrogen fluoride, and boron trifluoride. 

Cations like that present in (iv) exist in solutions of aromatic hydrocarbons in trifluoroacetic acid containing boron trifluoride, and in liquid hydrogen fluoride containing boron trifluoride. Sulphuric acid is able to protonate anthracene at a mero-position to give a similar cation. ... 

The relative basicities of aromatic hydrocarbons, as represented by the equilibrium constants for their protonation in mixtures of hydrogen fluoride and boron trifluoride, have been measured. The effects of substituents upon these basicities resemble their effects upon the rates of electrophilic substitutions a linear relationship exists between the logarithms of the relative basicities and the logarithms of the relative rate constants for various substitutions, such as chlorination and... 

The cr-complexes (iv) are thus the intermediates corresponding to the substitution process of hydrogen exchange. Those for some other substitutions have also been isolated in particular, benzylidyne trifluoride reacts with nitryl fluoride and boron trifluoride at — ioo°C to give a yellow complex. Above — 50 °C the latter decomposes to hydrogen fluoride, boron trifluoride, and an almost quantitative yield of tn-nitrobenzylidyne trifluoride. The latter is the normal product of nitrating benzylidyne trifluoride, and the complex is formulated as... 

Compounds containing fluorine and chlorine are also donors to BF3. Aqueous fluoroboric acid and the tetrafluoroborates of metals, nonmetals, and organic radicals represent a large class of compounds in which the fluoride ion is coordinating with trifluoroborane. Representative examples of these compounds are given in Table 5. Coordination compounds of boron trifluoride with the chlorides of sodium, aluminum, iron, copper, 2inc, tin, and lead have been indicated (53) they are probably chlorotrifluoroborates. 

Olefins are carbonylated in concentrated sulfuric acid at moderate temperatures (0—40°C) and low pressures with formic acid, which serves as the source of carbon monoxide (Koch-Haaf reaction) (187). Liquid hydrogen fluoride, preferably in the presence of boron trifluoride, is an equally good catalyst and solvent system (see Carboxylic acids). 

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

Toluene reacts with carbon monoxide and butene-1 under pressure in the presence of hydrogen fluoride and boron trifluoride to give 4-methyl-j iYbutyrophenone which is reduced to the carbinol and dehydrated to the olefin. The latter is cycHzed and dehydrogenated over a special alumina-supported catalyst to give pure 2,6- dim ethyl n aph th a1 en e, free from isomers. It is also possible to isomerize various dim ethyl n aph th a1 en es to the... 

Fluondes of boron, phosphorus, and antimony react with hydrogen fluoride, producing complex fluoroboric, fluorophosphoric, and fluoroantimonic acid,... 

Ethyl acetoacetate reacts with ehaleone in the presence of boron fluoride etherate affording 3-carbethoxy-2-methyl-4,6-diphenylpyryl-ium this can be hydrolyzed and decarboxylated to 2-methyl-4,6-diphenylpyrylium which should theoretically result from acetone and ehaleone. 

Besides acetophenone, this reaction was also applied to p-chloro- andp-methoxyacetophenone, and even to an aliphatic ketone, acetone (although the yield was stated to be only half as large as that obtained from mesityl oxide, i.e., less than 30%, Dorofeenko and co-workers reported a 45% yield of 2,4,6-trimethylpyrylium perchlorate from acetone, acetic anhydride, and perchloric acid), and is the standard method for preparing pyrylium salts with identical substituents in positions 2 and 4. The acylating agent may be an anhydride in the presence of anhydrous or hydrated ferric chloride, or of boron fluoride, or the acid chloride with ferric chloride.Schneider and co-workers ... 

In order to achieve high yields, the reaction usually is conducted by application of high pressure. For laboratory use, the need for high-pressure equipment, together with the toxicity of carbon monoxide, makes that reaction less practicable. The scope of that reaction is limited to benzene, alkyl substituted and certain other electron-rich aromatic compounds. With mono-substituted benzenes, thepara-for-mylated product is formed preferentially. Super-acidic catalysts have been developed, for example generated from trifluoromethanesulfonic acid, hydrogen fluoride and boron trifluoride the application of elevated pressure is then not necessary. 

Fluor-, of or combined with fluorine, fluoro-, fluo-, fluoride of (see instances following),. ammonium, n. ammonium fluoride, -an-thenchinon, n. fluoranthenequinone. -anti-mon, n. antimony fluoride, -arson, n. arsenic fluoride, -baryum, n. barium fluoride, -benzol, n. fluorobensene, fluobenaene. -bor, n. boron fluoride. -borsMure, /. fluo-boric acid. -brom, n. bromine fluoride, -chrom, n. chromium fluoride, -eisen, n. iron fluoride. 

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