Liquid ammonia solutions

The reaction between sodium acetylide in liquid ammonia solution and carbonyl compounds gives a-acetylenyl carbinols (compare Section 111,148), for example ... 

A second general reaction that proceeds by an SrnI mechanistic pattern involves aryl halides. Aryl halides undergo substitution by eertain nueleophiles by a ehain mechanism of the SrnI class.Many of the reactions are initiated photochemically, and most have been conducted in liquid ammonia solution. 

Sulfur—nitrogen anions in sulfur—liquid ammonia solutions... 

Preparation of pure K2O2, Rb202 and CS2O2 by this route is difficult because of the ease with which they oxidize further to the superoxides MO2. Oxidation of the metals with NO has been used but the best method is the quantitative oxidation of the metals in liquid ammonia solution (p. 78). The peroxides can be regarded as salts of the dibasic acid H2O2. Thus reaction with acids or water quantitatively liberates H2O2 ... 

The most ionic of the organometallic derivatives of Group 1 elements are the acetylides and dicarbides formed by the deprotonation of alkynes in liquid ammonia solutions ... 

Metal nitrides have also been prepared by adding KNH2 to liquid-ammonia solutions of the appropriate metal salts in order to precipitate the nitride, e.g. CU3N, Hg3N2, AIN, TI3N and BiN. 

Solvates are perhaps less prevalent in compounds prepared from liquid ammonia solutions than are hydrates precipitated from aqueous systems, but large numbers of ammines are known, and their study formed the basis of Werner s theory of coordination compounds (1891-5). Frequently, however, solvolysis (ammonolysis) occurs (cf. hydrolysis). Examples are ... 

Liquid ammonia solutions of lithium polysulfides have been characterized by Dubois et al. [18]. The least reduced polysulfide was shown to be 8 (not found previously in aquo) lying in a strongly temperature-dependent equilibrium with the radical 83 . 

Sharp KW, Koehler WH (1977) Synthesis and characterization of sodium polyselenides in liquid ammonia solution. Inorg Chem 16 2258-2265... 

The three picolines react with alkyl halides in liquid ammonia solution in the presence of sodamide to yield the corresponding monoalkylpyridines. a-Picoline also reacts with alkyl chlorides in the presence of sodamide either alone or in the presence of xylene to give a fair yield of monoalkylpyridine CjH N.CHjR. With y-picoliue under similar experimental conditions disubstitution of the alkyl group (CjHjN.CHRj) occurs to an appreciable extent. The preparation of tile three n-amylpyridines is described the 3- and 4-compounds by the liquid ammonia - sodamide method and the 2-compound by the sodamide-3 ene procedure. 

The lustrous black crystals of trirhenium nonabromide are not rapidly degraded on exposure to the atmosphere the crystals can be stored over desiccants for months without evidence of decomposition. The bromide dissolves fairly slowly and sparingly in ether and acetone. In methanol, the bromide gives yellow-orange solutions, but it is solvolyzed within minutes. Similarly, the bromide dissolves in water at room temperature to yield a violet solution which darkens rapidly, yielding a black precipitate, presumably the hydrated dioxide.9 Contrary to published work,10 the bromide does dissolve in ammonia with solvolysis, as is evidenced by lines attributable to ammonium bromide in x-ray diffraction data of the solid residue recovered from liquid ammonia solutions.11 Trirhenium nonabromide reacts with Lewis bases such as phosphines and amines to form a series of complexes of the type (base) 3Re3Br9.6... 

In contrast, these metals dissolve and undergo reaction only very slowly in liquid ammonia. Solutions containing alkali metals in liquid ammonia have been known for more than 140 years, and they have properties that are extraordinary. The extent to which the metals dissolve is itself interesting. The solubilities are shown in Table 10.3. 

Lithium reacts with acetylene in liquid ammonia solution to give the mono and dilithium acetylides, LiC=CH and LiC=CLi, with the evolution of hydrogen, which illustrates the slight acidity of acetylene. One commercial use of LiC=CI I is in one step of the synthesis of vitamin A. 

The synthesis of phosphazenes starting from aminophosphonium salts appears to be conveniently accomplished by the reaction of the phosphonium azide with sodamide in liquid ammonia solution 49... 

A somewhat more complex mechanism takes place with other H-atom donors, such as primary and secondary alcohols, either added to the liquid ammonia solution or used as the solvent (Andrieux et al., 1987). Instead of being totally reduced, the hydroxyalkyl radical, resulting from the H-atom abstraction from the alcohol, partly deprotonates, generating the anion radical of the parent carbonyl compound. The latter is then generated by... 

Smaller tetrel element clusters like the tetrahedral [E4] ions were observed for the first time in the alloy NaPb [38] and are present in AE phases for E = Si to Pb and A = Na-Cs. Although these phases are not soluble, ammoniates of [Pb4]" have been obtained from liquid ammonia solutions of the binary phase RbPb [39]. The Zintl phases Ai2Sii7 (A = K, Rb, Cs) and KgRb6Sii7, which in the solid state contain [Si4]" and [Sig]" anions in the ratio 2 1, readily dissolve in liquid ammonia, and recently it has been shown that both cluster anions [Si4]" [37] and [Sig]" [40] are retained in solution. Corresponding pentel element clusters in bulk solids are [Pn7] and [Pnn] (Table 1). 

The synthesis of sodium amide, NaNH2 (or sodamide ), by passing ammonia over heated sodium metal, was first reported almost two centuries ago. A number of studies have since been made of its properties, but no crystal structure has been reported. Sodamide is used as a strong base in organic chemistry (often in liquid ammonia solution). In contrast, sodium bis(trimethylsilyl)amide NaN(SiMe3)2 (or sodium hex-amethyldisilazide , NaHMDS), whose crystal structure is discussed later, is widely used for deprotonation reactions or base catalysed reactions due to its solubility in a wide range of non-polar solvents. An overview of some of the types of chemical reactions in which NaHMDS is used is presented in Scheme 2.3. 

Inorganic Chemical Technology, "McGraw-Hill, NY(1941), 89-98 17a)Coll, ChemRevs 26, pp l-104(1940)(Symposium on the chemistry of liquid ammonia solutions) 18)M< Serruys, JSocIngenieurs Automobile (Paris)... 

The [In(NH3)6]3+ cation has been identified in liquid ammonia solution,61 but attempts to prepare the perchlorate salt were unsuccessful.62 Mixed complexes such as [In(NH3)sBr]2+ have been postulated in liquid ammonia,63 but this has not been confirmed preparatively. Ethylenediamine yields the salt [Inen3](C104)3 on reaction with In(C104)3(aq) in ethanol,62 and the analogous nitrate64 and thiocyanate65 salts have also been prepared. 

Reduction. Benzene can be reduced to cyclohexane [110-82-7], C5H12, or cycloolefins. At room temperature and ordinary pressure, benzene, either alone or in hydrocarbon solvents, is quantitatively reduced to cyclohexane with hydrogen and nickel or cobalt (14) catalysts. Catalytic vapor-phase hydrogenation of benzene is readily accomplished at about 200°C with nickel catalysts. Nickel or platinum catalysts are deactivated by the presence of sulfur-containing impurities in the benzene and these metals should only be used with thiophene-free benzene. Catalysts less active and less sensitive to sulfur, such as molybdenum oxide or sulfide, can be used when benzene is contaminated with sulfur-containing impurities. Benzene is reduced to 1,4-cydohexadiene [628-41-1], C6HS, with alkali metals in liquid ammonia solution in the presence of alcohols (15). 

One of the most interesting processes in electrically initiated polymerization was an initiation with the solvated electron proposed by Laurin and Parravano (22), who studied electro-anionic polymerization of 4-vinylpyridine in liquid ammonia solution of alkali metal salts in the temperature range — 33 to — 78° C. Rapid and efficient polymerization occurred and conversions of monomer to polymers formed exclusively at the cathode in the form of an orange-red, porous, solid deposit, suggesting the formation of a pile of living polymers. 

In a similar manner the so-called Zintl salts composed of alkali metal cations and clusters of metals as anions (see Chapter 16) were known in liquid ammonia solution but proved to be impossible to isolate Upon removal of the solvent they reverted to alloys. Stabilization of the cations by complexation with macrocyclic ligands allowed the isolation and determination of the structures of these compounds. 

Here ArX is the halothiophene and ArY the product. The nature of the initiation and termination steps is not known. Thus irradiation of 3-bromothiophene in liquid ammonia in presence of potassium acetone enolate gives the monothienylation product (492 51%) and the dithienylation product (493 25%). Instead of employing photostimulation, the reaction can be brought about in lower yields by dissolving sodium or potassium metal in the liquid ammonia solution. Here the corresponding alcohol is a side product. 

M being a univalent metal and X a univalent acid radical. Arsenic may similarly be replaced by metals, but the replacement cannot always be predicted from the position of arsenic in the electrochemical series, this power of replacement being a highly specific property which depends on the nature of the metal and the conditions of the experiment. Such reactions in liquid ammonia solutions show that in the following series an element will in general replace any subsequent element, if it is present in an analogous anion 2 I, S, Se, Te, As, Sb, Sn, Bi, Pb. 

The toluene (Merck reagent grade) was kept dry by storage over sodium wire. Dry thiophene-free benzene may be used instead but is less convenient because it freezes when added to the liquid ammonia solution. 

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