Acid metal fluorides, decompositions

The pyrolytic decomposition of the sodium salts of various fluorinated carboxylic acids to give isomeric unsaturated compounds has also been reported. The products were identified as alkenes with the C = C bond inside the carbon chain, mainly alk-2-enes. This isomerization may be catalyzed by the coal-like products formed during the pyrolytic decarboxylation of the salts, but the metal fluoride formed in the reaction may also be responsible for the isomerization. When potassium perfluoro(5-chloropentanoate) is heated in a rocking autoclave at 300 C for 2 hours, perfluorobut-2-ene (2b) is isolated in 82% yield.This is only possible by migration of the double bond away from the terminal position after carbon dioxide elimination and halogen exchange to form potassium chloride. ... 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by inhalation. A corrosive irritant to the eyes, skin, and mucous membranes. With the appropriate conditions it undergoes hazardous reactions with formic acid, hydrogen fluoride, inorganic bases, iodides, metals, methyl hydroperoxide, oxidants (e.g., bromine, pentafluoride, chlorine trifluoride, perchloric acid, oxygen difluoride, hydrogen peroxide), 3-propynol, water. When heated to decomposition it emits toxic fumes of POx. 

Disulfuryl fluoride is a clear colorless liquid with a boiling point of 51°. Its vapor pressure over the temperature range —28 to 43° follows the equation logioP(mm.) = 8.015— 1662/T. It has an inhalation toxicity of the same order as that of phosgene, and should be handled only in a well-ventilated area. Its thermal decomposition to sulfur trioxide and sulfuryl fluoride is not very appreciable below 200° but is rapid at 400-500°. In the presence of metal fluorides such as ceaum or sodium fluoride, however, its decomposition point is considerably low er. It hydrolyzes rather slowly to give fluorosulfuric acid. It is not very soluble in cold concentrated sulfuric acid or fluorosulfuric acid, but is soluble in acetonitrile, ethyl ether, carbon tetrachloride, monofluorotrichloromethane, and benzene. 

ACID AMMONIUM FLUORIDE (1341-49-7) FiH H4N Reacts with water, forming a weak solution of hydrofluoric acid. Violent reaction with bases, releasing ammonia gas. Attacks glass, cement, and most metals in the presence of moisture. Upon contact with moisture and metal, this material may release flammable hydrogen gas which may collect in enclosed spaces. Do not use aluminum, nickel, or steel containers. When heated to decomposition, emits toxic and corrosive fumes of ammonia, hydrogen fluoride, and nitric oxides. 

LEAD FLUOROBORATE (13814-96-5) Pb (BF4)2 Decomposes in water or acids, forming ionic lead and fluoboric acid solution. Aqueous solution incompatible with sulfuric acid, alkalis, ammonia, aliphatic amines, alkanolamines, alkylene oxides, amides, epichlorohydrin, organic anhydrides, isocyanates, nitromethane, vinyl acetate. Corrodes aluminum and most other metals. Thermal decomposition releases lead fumes and hydrogen fluoride gas. On small fires. 

The decomposition of inorganic substances can be accomplished with a mixture of hydrochloric and nitric acids in a closed vessel (pressure digestion). Silicate-containing minerals and glasses require the addition of hydrofluoric acid, and the presence of perchloric acid, phosphoric acid, or sulfuric acid is sometimes useful as well [80]. The resulting metal fluorides can be redissolved by adding a solution of boric acid. The same procedure is effective for ores and slags as well as quartz [81 j. 

The mechanism of the decomposition reaction into metal fluorides has not been elucidated so far. In the first place, metal trifluoroacetates themselves have been relatively less studied among the salts of carboxylic acids. Synthesis and properties of only a few metal trifluoroacetates have been reported (Killings, 1974 Khristov, 1998 Tada, 1999). Thermogravimetry-mass spectrometry (TG-MS) analysis has been carried out to examine the deconposition reaction oflanthanum trifluoroacetate (Eujihara, 2000b). The reaction suggested is... 

Complexing agents, which act as buffers to help control the pH and maintain control over the free metal—salt ions available to the solution and hence the ion concentration, include citric acid, sodium citrate, and sodium acetate potassium tartrate ammonium chloride. Stabilizers, which act as catalytic inhibitors that retard the spontaneous decomposition of the bath, include fluoride compounds thiourea, sodium cyanide, and urea. Stabilizers are typically not present in amounts exceeding 10 ppm. The pH of the bath is adjusted. 

Alternative paths for decomposition of the metal carboxylate can lead to ketones, acid anhydrides, esters, acid fluorides (1,11,22,68,77,78), and various coupling products (21,77,78), and aspects of these reactions have been reviewed (1,11). Competition from these routes is often substantial when thermal decomposition is carried out in the absence of a solvent (Section III,D), and their formation is attributable to homolytic pathways (11,21,77,78). Other alternative paths are reductive elimination rather than metal-carbon bond formation [Eq. (36)] (Section III,B) and formation of metal-oxygen rather than metal-carbon bonded compounds [e.g., Eqs. (107) (119) and (108) (120). Reactions (36) and (108) are reversible, and C02 activation (116) is involved in the reverse reactions (48,120). 

It was found that the addition of 0.5% hydrogen fluoride to red fuming nitric acid (RFNA) removed the large pressure increase observed when normal RFNA was stored in the aluminum tanks used in certain rocket engine systems. Apparently this small amount of HF passivated the surface of the metal and prevented it from reacting with RFNA to generate decomposition gases. 

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