Rubidium reduction

Reduction of the chlorides by Ba, Na or Ca is a satisfactory method of preparing small amounts of pure Rb and Cs. Rubidium chloride is dissolved in barium azide aq sol and evaporated at 25°C to dryness. The intimate mixture is then heated under vacuum. The BafNjIj decomposes at ca. 100-200°C to Ba metal, which reduces RbCI to Rb this distills at temperatures low enough to prevent contamination by Ba vapor. The most widely employed method uses Ca as the reducing agent ... 

Metals react with nonmetals. These reactions are oxidation-reduction reactions. (See Chapters 4 and 18). Oxidation of the metal occurs in conjunction with reduction of the nonmetal. In most cases, only simple compounds will form. For example, oxygen, 02, reacts with nearly all metals to form oxides (compounds containing O2-). Exceptions are the reaction with sodium where sodium peroxide, Na202, forms and the reaction with potassium, rubidium, and cesium where the superoxides, K02, Rb02, and Cs02 form. 

Stereospecific ketone reduction was also observed (Giordano et al. 1985) with potassium, rubidium, and cesium (but not with sodium) in tertiary alcohols (but not in secondary or primary alcohols). The undesirable dimerization probably proceeds more readily in the case of sodium. Tertiary alcohols are simply more acidic than primary or secondary alcohols. It is reasonable to point out that the ketone-to-alcohol reduction of 3a-hydroxy-7-oxo-5p-cholic acid by alkali metals is a key step in the industrial synthesis of 3a,7p-dihydroxy-5p-cholic acid. 

Rubidium does not exist in its elemental metallic form in nature. However, in compound forms it is the 22nd most abundant element on Earth and, widespread over most land areas in mineral forms, is found in 310 ppm. Seawater contains only about 0.2 ppm of rubidium, which is a similar concentration to lithium. Rubidium is found in complex minerals and until recently was thought to be a rare metal. Rubidium is usually found combined with other Earth metals in several ores. The lepidolite (an ore of potassium-lithium-aluminum, with traces of rubidium) is treated with hydrochloric acid (HCl) at a high temperature, resulting in lithium chloride that is removed, leaving a residue containing about 25% rubidium. Another process uses thermochemical reductions of lithium and cesium ores that contain small amounts of rubidium chloride and then separate the metals by fractional distillation. 

One problem in refining cesium is that it is usually found along with rubidium therefore, the two elements must be separated after they are extracted from their sources. The main process to produce cesium is to finely grind its ores and then heat the mix to about 600°C along with liquid sodium, which produces an alloy of Na, Cs, and Ru, which are separated by fractional distillation. Cesium can also be produced by the thermochemical reduction of a mixture of cesium chloride (CsCl) and calcium (Ca). 

Rubidium metal may be obtained from its carbonate, hydroxide or chloride by reduction with magnesium or calcium at high temperatures in the presence of hydrogen ... 

Pt(II) compound reactivation, 37 201 Pt(IV) compound reduction, 37 201 rate-determining step, 37 199-201 tetrachloride, 4 187-188 tetracyanide anions, as one-dimensional electrical conductors, 26 235-268 anion-deficient structures anhydrous compounds, 26 252-254 dimerization, 26 249-251 hydrated derivatives, 26 245-252 physics, 26 260-263 with potassium bromide, 26 248-249 with rubidium chloride, 26 249-250 cation-deficient compounds, 26 244, 254-256... 

The hydrogenation of phenanthridine at 250 °C under pressure in the presence of a sodium-rubidium catalyst in benzene is reported to give octahydrophenanthridines. Acridine similarly forms a variety of reduction products (71JOC694). 

A unique feature of azoles amongst five membered heterocycles is that they can act both as the carbon or the heteroatom donor during the bond formation. This possibility is frequently exploited in synthetic transformations. Pyrrole, for example, coupled effectively with bromoarenes in the presence of palladium based catalysts (6.67.), The use of PBuj as ligand and rubidium carbonate as base allowed for the reduction of catalyst loading to 1% without significant deterioration of the yield"... 

To purify the cesium (rubidium) from the admixture of the zirconium used for reduction, repeat the distillation from one ampoule into another one. For this purpose, carefully heat the alkali metal in the ampoule with a gas burner until boiling begins and perform distillation slowly (during 0.5 hour). After this, seal the ampoule with the metal. Write the equation of the reaction. 

The hydrated double oxalate of rubidium and thallium has been formulated as Rb[Tlox2(H20)2]-2H20. Water is lost on heating, and Tl111 undergoes reduction to Tl1, so that final products are Tl1 oxide and Rb2CO3.40°... 

Reduction of ketones. Reduction of ketones with metals in an alcohol is one of the earliest methods for effecting reduction of ketones, and is still useful since it can proceed with stereoselectivity opposite to that obtained with metal hydrides.1 An example is the reduction of the 3a-hydroxy-7-ketocholanic acid 1 to the diols 2 and 3. The former, ursodesoxycholic acid, a rare bile acid found in bear bile, is used in medicine for dissolution of gallstones. The stereochemistry is strongly dependent on the nature of the reducing agent (equation I).2 Sodium dithionite and sodium borohydride reductions result mainly in the 7a-alcohol, whereas reductions with sodium or potassium in an alcohol favor reduction to the 7p-alcohol. More recently3 reduction of 1 to 2 and 3 in the ratio 96 4 has been achieved with K, Rb, and Cs in f-amyl alcohol. Almost the same stereoselectivity can be obtained by addition of potassium, rubidium, or cesium salts to reductions of sodium in t-amyl alcohol. This cation effect has not been observed previously. 

Potassium, rubidium, and cesium metals are produced by chemical reduction rather than by electrolysis. Sodium is the reducing agent used in potassium production, and calcium is the reducing agent used for preparing rubidium and cesium. 

The reduction of 2,3,4,5-tetraethyl-Tchloroarsole 18 (E = As) or -stibole 18 (E = Sb) with alkali metals such as sodium, potassium, rubidium, and cesium afforded the corresponding 2,2, 3,3, 4,4, 5,5 -octaethyl-l,l -biarsole/stibole 19 (Equation 13) <20040M3417>. 

At the moment we are investigating the influence of different donor ligands on the structural features especially of the rubidium and cesium derivatives. Such adducts are prepared by adding the corresponding ligand to a suspension of hypersilyl rubidium 4 or cesium 5 in npentane until a clear solution is obtained. Although, in some cases side-reactions occur, such as deprotonation (diphenylmethane) or reduction (pyrene, bipyridine). In addition to the toluene solvates 4a and Sa already mentioned above, the only two crystalline derivatives isolated so far are the adducts with THF as a typical cr-donor and with biphenyl as a further Ji-donor (Fig. 6 and Fig. 7). 

Rubidium Impurity in lepidolite, Li2(F,OH)2Al2(Si03)3 Reduction of RbOH with Mg and H2... 

Unfortunately, the absence of X-ray structural information and magnetic evidence has prevented the establishment of the formula Xe+[PtFe] for the 1 1 adduct, although the derivation of rubidium hexafluoroplatinate(V) from this compound in the oxidatively and reductively neutral solvent iodine penta-fluoride indicates that it is a hexafluoroplatinate(V). Some support for the... 

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