Bromides, molten

Iwagishi T, Yamamoto H, Koyama K et al (2002) Effect of water content and the effect of adding ethylene glycol on the 1 - ethyl-3-methyUmidazolium bromide molten salt electrodeposition of Zn using zinc bromide 70 671-678 (in Japanese)... 

Figure 20 shows the ionic conductivity as a function of the mole percent of AlCl, for the molten salts. The molten salts were formed with the AlCl, composition ranging from 30 to 70 mol%, although both pyridinium salts and aluminum chloride are crystalline solids at room temperature. These molten salts have high ionic conductivities of about 10 S cm over the entire molar ratios. The conductivity of the molten salts depends on the anion species of the pyridinium salts, and the chloride molten salts have higher conductivities than do the bromide molten salts. 

The anhydride can be made by the Hquid-phase oxidation of acenaphthene [83-32-9] with chromic acid in aqueous sulfuric acid or acetic acid (93). A postoxidation of the cmde oxidation product with hydrogen peroxide or an alkaU hypochlorite is advantageous (94). An alternative Hquid-phase oxidation process involves the reaction of acenaphthene, molten or in alkanoic acid solvent, with oxygen or acid at ca 70—200°C in the presence of Mn resinate or stearate or Co or Mn salts and a bromide. Addition of an aHphatic anhydride accelerates the oxidation (95). 

Many organic hahdes, especially alkyl bromides and iodides, react direcdy with tin metal at elevated temperatures (>150° C). Methyl chloride reacts with molten tin metal, giving good yields of dimethyl tin dichloride, which is an important intermediate in the manufacture of dimethyl tin-ha sed PVC stabilizers. The presence of catalytic metallic impurities, eg, copper and zinc, is necessary to achieve optimum yields (108) ... 

Cerous bromide [14457-87-5] CeBr, and praseodymium bromide [13536-53-3] PrBr, are claimed to be suitable for a molten salt bath used for the reduction of uranium oxide by magnesium (16). PrBr is claimed to be alight filter in a cathode ray tube (17). 

Early in their work on molten salt electrolytes for thermal batteries, the Air Force Academy researchers surveyed the aluminium electroplating literature for electrolyte baths that might be suitable for a battery with an aluminium metal anode and chlorine cathode. They found a 1948 patent describing ionically conductive mixtures of AICI3 and 1-ethylpyridinium halides, mainly bromides [6]. Subsequently, the salt 1-butylpyridinium chloride/AlCl3 (another complicated pseudo-binary)... 

The use of ionic liquids as reaction media for the palladium-catalyzed Heck reaction was first described by Kaufmann et ak, in 1996 [85]. Treatment of bromoben-zene with butyl acrylate to provide butyl trans-cinnamate succeeded in high yield in molten tetraallcylammonium and tetraallcylphosphonium bromide salts, without addition of phosphine ligands (Scheme 5.2-16). 

Gold phthalocyanine (PcAu) is prepared by the reaction of gold(I) bromide with molten isoindolinediimine.292... 

G. J. Janz, R. P. T. Tomkins, C. B. Allen, J. R. Downey, Jr., and K. Singer, J. Rhys. Chem. Ref Data 6 (1977) 409 Molten Salts, Vol. 4, Part 3 Bromides and Mixtures Iodides and Mixtures, American Chemical Society-American Institute of Physics-National Bureau of Standards, Washington, DC, 1977. 

Apart from the fluoride, mercuric halides react explosively with potassium like all analogues of the other metals already mentioned. With mercurous salts, the reaction seems less violent since with mercurous chloride, molten potassium causes the mixture to incandesce without ever combusting. It is likely that other metals react too an extreme violent reaction was mentioned between indium and mercuric bromide. 

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... 

Lead oxide is soluble in molten phenol (45-60°C) at a level of 20 wt%. Evaporation of phenol from such a solution yields lead (II) phenoxide. Reactions between lead oxide and quaternary bromide in phenol depend on temperature ... 

A mixture with sodium explodes under a hammer blow, while potassium explodes strongly under the molten bromide [1]. Tin reacts violently with the bromide [2],... 

Phosphorus reacts violently with the molten bromide. 

Potassium ignites in fluorine and in dry chlorine (unlike sodium). In bromine vapour it incandesces, and explodes violently in liquid bromine. Mixtures with iodine incandesce on heating, and explode weakly on impact. Potassium reacts explosively with molten iodine bromide and iodine, and a mixture with the former is shock-sensitive and explodes strongly. Molten potassium reacts explosively with iodine pentafluoride [1], Contact with iodine trichloride causes ignition [2],... 

Impact causes a mixture of potassium and anhydrous hydrogen chloride to explode very violently [1], Molten potassium ignites in contact with hydrogen chloride, hydrogen bromide or hydrogen iodide [2],... 

Sodium ignites in fluorine gas but is inert in the liquefied gas [1]. Cold sodium ignites in moist chlorine [2] but may be distilled unchanged in the dry gas [1]. Sodium and liquid bromine appear to be unreactive on prolonged contact [3], but mixtures may be detonated violently by mechanical shock [4]. Finely divided sodium luminesces in bromine vapour [1], Iodine bromide or iodine chloride react slowly with sodium, but mixtures will explode under a hammer-blow [1]. Interaction of iodine pentafluoride with solid sodium is initially vigorous, but soon slows with film-formation, while that with molten sodium is explosively violent... 

In many ways, chloroaluminate molten salts are ideal solvents for the electrodeposition of transition metal-aluminum alloys because they constitute a reservoir of reducible aluminum-containing species, they are excellent solvents for many transition metal ions, and they exhibit good intrinsic ionic conductivity. In fact, the first organic salt-based chloroaluminate melt, a mixture of aluminum chloride and 1-ethylpyridinium bromide (EtPyBr), was formulated as a solvent for electroplating aluminum [55, 56] and subsequently used as a bath to electroform aluminum waveguides [57], Since these early articles, numerous reports have been published that describe the electrodeposition of aluminum from this and related chloroaluminate systems for examples, see Liao et al. [58] and articles cited therein. 

Example During the electrolysis of molten lead (II) bromide ... 

Wittig olefination of 2-nitro-Z-cinnamaldehyde (1300) with the phosphonium bromide 1301 led to the diene 1302. The Diels-Alder cycloaddition of 1302 with maleimide (1303), followed by dehydrogenation with DDQ, afforded the phthali-mide 1304. Double deoxygenation of 1304 with triphenylphosphine (PPhs) in collidine gave O-methylarcyiiaflavin B (1305). Finally, heating of 1305 with molten pyridine hydrochloride led to arcyriaflavin B (346) (759) (Scheme 5.215). 

The halogen fluorides are usually regarded as normal covalent hquids, in spite of the fact that the iodine chlorides and iodine bromide conduct electricity both in the molten state and in solution (2). 

Bismuth reacts with chlorine, bromine and iodine vapors forming chloride, bromide and iodide of the metal, respectively. Molten bismuth and sulfur combine to form bismuth sulfide, Bi2S3. 

Pacholec, F., and Poole, C.F., Stationary phase properties of the organic molten salt ethylpyridinium bromide in gas chromatography, Chromatographia, 17, 370-374,... 

Reactions conducted in molten quaternary phosphonium salts require no other solvent (199). This material serves as both promoter and reaction medium. Care must be exercised in choosing the salt in such a reaction, since any decomposition could lead to products such as trialkylphosphines and alkyl halides which are expected to be deleterious to catalyst performance. Tetrabutylphosphonium bromide is reported to provide a stable catalyst medium which can be recycled (199, 200), but other related salts show evidence of thermal decomposition during catalytic reactions. Experiments in tetrabutylphosphonium acetate, for example, are found to produce large amounts of methyl and ethylene glycol acetate esters (199). 

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