Metal-ammonia stability

A study of the lithium-ammonia reduction of 14-en-16-ones would extend our understanding of the configuration favored at C-14 in metal-ammonia reductions. Although several simple 14-en-16-ones are known, their reduction by lithium and ammonia apparently has not been described in the literature. Lithium-ammonia reduction of A-nortestosterone, a compound that structurally is somewhat analogous to a 14-en-16-one, affords roughly equal amounts of the 5a- and 5 -dihydro-A-nortestosterones. " This finding was interpreted as indicating that there is little difference in thermodynamic stability between the two stereoisomeric products. 

F.Ephraim, Ber 46, 3103-31(1913) CA 8, 597 (1914) (The nature of residual valence influence of the anion on the stability of complex cations in metal ammonia compds) 7)... 

Solutions of alkali metals in ammonia have been the best studied, but other metals and other solvents give similar results. The alkaline earth metals except- beryllium form similar solutions readily, but upon evaporation a solid ammoniste. M(NHJ)jr, is formed. Lanthanide elements with stable +2 oxidation states (europium, ytterbium) also form solutions. Cathodic reduction of solutions of aluminum iodide, beryllium chloride, and teUraalkybmmonium halides yields blue solutions, presumably containing AP+, 3e Be2, 2e and R4N, e respectively. Other solvents such as various amines, ethers, and hexameihytphosphoramide have been investigated and show some propensity to form this type of solution. Although none does so as readily as ammonia, stabilization of the cation by complexation results in typical blue solutions... 

The next development was a Pt(II) catalyzed process in H2SO4 at 180°, where the metal was stabilized with a 2,2 -bipyrimidine ligand or alternatively with two ammonias. The latter was more active but deactivated faster, while the diazene was more robust but less active. 

Movement through the phases is reflected by significant changes in leachate and gas quality. Nonconservative constituents of leachate (primarily organic in nature) tend to decompose and stabilize with time, whereas conservative constituents will remain long after waste stabilization occurs. Conservative constituents include various heavy metals, ammonia, chloride, and sulfide. 

Deigen and Pekar (16) have shown that in the polarons the energy correction caused by the hyperfine interaction equals zero in the first approximation. Hence, the width of the polaron line determined by the hyperfine interaction also equals zero. At the same time for the local electron centers such an interaction is actually a predominant factor which determines the width of the line. This makes it possible to distinguish by way of experiments the polarons from the local electron centers. Evidently, the solvated electrons produced during irradiation of the polar liquids are the mobile polarons. At low temperatures the polarons are stabilized in the form of local electron centers (peculiar F-centers) (6, 19). Actually, in the metal-ammonia solutions the width of the EPR line of the solvated electron comprises some hundredths of oersted however, the freezing of the solution at 77 °K. results in widening of this line up to 3.4 (37) or 11 (58) oe. 

In a study of electron-transfer reactions. House has examined the stabilities of the anion radicals derived from a number of y-cyclopropyl-ap-unsaturated ketones. It would appear that for the conversion of substrates containing the unit depicted by (240) into (241) a rearrangement rate in excess of 10 s is necessary in order to detect the anion radical intermediate present in metal-ammonia reductions. A rate of ca. 10 s is likewise required in lithium dimethylcuprate reactions. ... 

Stability. On evaporating freshly prepared metal-ammonia solutions, a residue of the metal is left indicating that there are no chemical changes in the solution. But on allowing the solution to stand for some time, the blue color gradually disappears with evolution of hydrogen according to the reaction... 

He also interpreted much of the data at low concentrations as an electrolyte solution while at high concentrations they were discussed as liquid metal. Much of the earlier studies of trapped electrons were dominated by the study of metal ammonia solutions, in part because of their exceptional stability. These studies were first collectively presented in the proceedings of Colloque Weyl I in 1963 (Lepoutre and Sienko, 1963). 

A third solution is via primary reduction to the benzylic alcohol which is then stabilized as its anion during the metal-ammonia reduction [119, 217], and can be reoxidized by the Oppenauer method (Fig. 9.9). 

The methoxylated dienes may be prepared from the corresponding arene derivative by metal-ammonia reduction, and react with the metal carbonyl to give XCI in yields of 70-80%. The best yields of demethoxylated aromatic derivatives are obtained when M = Cr, and the stability of the complexes follows the sequence Cr > W > Mo. The organic ligand may be liberated by the combined action of light and air. 

The oxide is soluble in ammonia to give the complex [AglNHjlj] (linear). On heating, silver(I) oxide loses oxygen to give the metal (all the coinage metal oxides have low thermal stability and this falls in the order Cu > Ag > Au). 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

These monomers provide a means for introducing carboxyl groups into copolymers. In copolymers these acids can improve adhesion properties, improve freeze-thaw and mechanical stability of polymer dispersions, provide stability in alkalies (including ammonia), increase resistance to attack by oils, and provide reactive centers for cross-linking by divalent metal ions, diamines, or epoxides. 

Pyrrole is soluble in alcohol, benzene, and diethyl ether, but is only sparingly soluble in water and in aqueous alkaUes. It dissolves with decomposition in dilute acids. Pyrroles with substituents in the -position are usually less soluble in polar solvents than the corresponding a-substituted pyrroles. Pyrroles that have no substituent on nitrogen readily lose a proton to form the resonance-stabilized pyrrolyl anion, and alkaU metals react with it in hquid ammonia to form salts. However, pyrrole pK = ca 17.5) is a weaker acid than methanol (11). The acidity of the pyrrole hydrogen is gready increased by electron-withdrawing groups, eg, the pK of 2,5-dinitropyrrole [32602-96-3] is 3.6 (12,13). 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Can catch fire when in contact with porous materials such as wood, asbestos, cloth, soil, or rusty metals Stability During Transport Stable at ordinary temperatures, however when heated this material can decompose to nitrogen and ammonia gases. The decomposition is not generally hazardous unless it occurs in confined spaces Neutralizing Agents for Acids and Caustics Flush with water and neutralize the resulting solution with calcium hypochlorite Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

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