Sodium solution in liquid

Electrochemical generation of solvated electrons was first observed in 1897 by Cady who found that when sodium solutions in liquid ammonia are electrolysed the blue coloration intensity increases at the cathode. All information on cathode generation of solvated electrons remained at this qualitative level for over half a century until Laitinen and Nyman made the first attempt to quantitatively investigate the kinetics of this process. This work, however, remained isolated for a long time and only after 20 years, with the awakening of interest in the chemistry of solvated electrons, were systematic studies into the kinetics of electrode reactions of solvated electrons started, almost simultaneously by three groups of researchers in Southampton Tokyo and Moscow In Moscow these studies... 

These methods are linked in that the solvents which dissolve alkali metals yielding solvated electrons and solvated cations are most commonly used for electrochemical generation of solvated electrons. One of the first experiments on such a generation was performed in 1897 by Cady who noticed an increase in the intensity of the blue coloration at the Pt cathode in a dilute sodium solution in liquid ammonia at —34 °C... 

Silver black was also prepared by application of some other succession of the solutions being flowed to the sodium solution in liquid ammonia was flowed to the solution of AgNOs in liquid ammonia. Flakes of silver black, settling at the bottom of a glass, were therewith formed. Formation of the colloidal particles was not observed in this case. Washing out the sodium ions was performed by decantation. Afterwards, the sample was dried in air at room temperature (sample 3). 

The alkali metals have the interesting property of dissolving in some non-aqueous solvents, notably liquid ammonia, to give clear coloured solutions which are excellent reducing agents and are often used as such in organic chemistry. Sodium (for example) forms an intensely blue solution in liquid ammonia and here the outer (3s) electron of each sodium atom is believed to become associated with the solvent ammonia in some way, i.e. the system is Na (solvent) + e" (sohem). 

A solution of mono-sodium acetylide in liquid ammonia is formed by passing excess of acetylene gas into the suspension of sodamide ... 

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

Ccasionally the reaction mixture does not become completely black nor free from suspended solid here the acetylide is in an insoluble (or sparingly soluble) form, but it gives satisfactory results in the preparation of hex-l-yne. The saturated solution of the soluble form of mono-sodium acetylide in liquid ammonia at — 34° is about i- M. 

The formation of the above anions ("enolate type) depend on equilibria between the carbon compounds, the base, and the solvent. To ensure a substantial concentration of the anionic synthons in solution the pA" of both the conjugated acid of the base and of the solvent must be higher than the pAT -value of the carbon compound. Alkali hydroxides in water (p/T, 16), alkoxides in the corresponding alcohols (pAT, 20), sodium amide in liquid ammonia (pATj 35), dimsyl sodium in dimethyl sulfoxide (pAT, = 35), sodium hydride, lithium amides, or lithium alkyls in ether or hydrocarbon solvents (pAT, > 40) are common combinations used in synthesis. Sometimes the bases (e.g. methoxides, amides, lithium alkyls) react as nucleophiles, in other words they do not abstract a proton, but their anion undergoes addition and substitution reactions with the carbon compound. If such is the case, sterically hindered bases are employed. A few examples are given below (H.O. House, 1972 I. Kuwajima, 1976). 

The chemical resistance of PTFE is exceptional. There are no solvents and it is attacked at room temperature only by molten alkali metals and in some cases by fluorine. Treatment with a solution of sodium metal in liquid ammonia will sufficiently alter the surface of a PTFE sample to enable it to be cemented to other materials using epoxide resin adhesives. 

Herrmann et al. reported for the first time in 1996 the use of chiral NHC complexes in asymmetric hydrosilylation [12]. An achiral version of this reaction with diaminocarbene rhodium complexes was previously reported by Lappert et al. in 1984 [40]. The Rh(I) complexes 53a-b were obtained in 71-79% yield by reaction of the free chiral carbene with 0.5 equiv of [Rh(cod)Cl]2 in THF (Scheme 30). The carbene was not isolated but generated in solution by deprotonation of the corresponding imidazolium salt by sodium hydride in liquid ammonia and THF at - 33 °C. The rhodium complexes 53 are stable in air both as a solid and in solution, and their thermal stability is also remarkable. The hydrosilylation of acetophenone in the presence of 1% mol of catalyst 53b gave almost quantitative conversions and optical inductions up to 32%. These complexes are active in hydrosilylation without an induction period even at low temperatures (- 34 °C). The optical induction is clearly temperature-dependent it decreases at higher temperatures. No significant solvent dependence could be observed. In spite of moderate ee values, this first report on asymmetric hydrosilylation demonstrated the advantage of such rhodium carbene complexes in terms of stability. No dissociation of the ligand was observed in the course of the reaction. 

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

Initiation presumably involves metal alkyls as the primary source of carbanions. These are immediately available from the Grignard reagents, organosodium compounds, or sodium amide used as catalysts when the alkali metal itself or its solution in liquid ammonia is used, addition to the monomer may precede actual initiation. ... 

Triphenylmethyl sodium and triphenylmethyl potassium conduct in liquid ammonia although they slowly react with that solvent.887 888 When the liquid ammonia is allowed to evaporate from a solution of triphenylmethyl sodium in ammonia, the residue is a colorless mixture of sodamide and triphenylmethane. The sodium-tin and sodium-germanium compounds analogous to sodium triphenylmethide are also strong electrolytes in liquid ammonia. Sodium acetylide in liquid ammonia is dissociated to about the same extent as sodium acetate in water.889... 

Sodium dissolves in liquid ammonia forming an unstable blue solution. The reaction is slow. Sodium amide and hydrogen are generated ... 

Sodium azide is prepared by reacting sodium amide with nitrous oxide. The amide is heated with nitrous oxide at 200°C or its solution in liquid ammonia is treated with nitrous oxide at ambient temperature ... 

A solution of 2.5 mol of sodium acetylidc in liquid NHj (p. 17-19) is cooled to —40 C and a vigorous stream of acetylene is introduced for 2 min (31/mjn). The alkyl bromide (2.0 mol) is then added dropwise over 1 h while maintaining the temperature as close as possible to -38 C Stirring at this temperature is continued for another 1.5 h (for the type of stirrer see fig 3), then 300 ml of high-boiling petroleum ether (b.p. >170 C) is added. The mixture is cautiously poured onto 2 kg of finely crushed ice in a 5-1 wide-necked round-bottomed (fig. 13) or conical flask. The reaction flask is rinsed with a small amount of ice water which is added to the bulk. After separation of the layers, three extractions with small amounts of petroleum ether are carried out The extracts are washed with dilute hydrochloric acid and subsequently dried over MgS04. Isolation is carried out as described in exps. 1 and 3, and in Chap. 1-2.6. The product is carefully redistilled through a 40-cm Widmer column. 1-Pentyne, b.p. 

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