Dissolving metals amides

Potassium dissolves in Hquid ammonia, but the conversion of a small amount of the metallic potassium to the metallic amide takes several days. By applying the same technique using sodium metal, sodium amide [7782-92-5] NaNH2, a white soHd, can be formed. 

Dissolved metals and metal-containing surfaces play an important role in the transformation of organic contaminants in the subsurface environment. Metal ions can catalyze hydrolysis in a way similar to acid catalysis. Organic hydrolyzable compounds susceptible to metal ion catalysis include carboxylic acids, esters, amides, anilides, and phosphate-containing esters. Metal ions and protons... 

Huang, C. Stone, A.T. Hydrolysis of naptalam and structurally related amides inhibition by dissolved metal ions and metal hydroxide surfaces. J. Agric. Food Chem. 1999, 47, 4425. 

Sodium Amide or Sodamide, NaNH2. Wh crysts, mp 206.4° dissolves in liq NH3 and is vigorously hydrolyzed by HjO. Was first prepd ca 1810 by Gay-Lussac and Thenard by the action of NH3 gas on molten metallic Na heated to 300°. Can also be prepd by dissolving metallic Na in liq NH3 and then placing in the soln a a spiral of. Fe wire, which catalytically accelerates the otherwise very slow reaction Na + NH NaNH2 + H Mixts of sodamide with nitrates and chlorates expl when triturated (Ref 1, p 255)... 

After Abe s work the problem again lay dormant for a number of years until it was taken up by Wilmarth and his co-workers. Claeys, Baes, and Wilmarth (29) in 1948 reported that a liquid ammonia solution of potassium metal rapidly catalyzed o-p H2 conversion, a half-time in solution of 37 sec. being obtained at —53°. In order to establish that this result was due to dissolved metal and not to amide ion impurity, Claeys, Dayton, and Wilmarth (30) studied the o-p H2 conversion in the presence of potassium amide in liquid ammonia. Rates were obtained comparable with those occurring with the metal solution. The mechanism of the conversion was different for the two cases, however, since the amide solution also catalyzed exchange between gaseous deuterium and liquid ammonia, while the metal solution did not. It was assumed that the metal acted by a paramagnetic mechanism and the amide ion by a chemical mechanism. In the same note Claeys, Dayton, and Wilmarth (30) reported confirmation of Wirtz and Bonhoeffer s results on the aqueous alkali system and questioned the validity of Abe s objections. 

Ammonia dissolves alkali metals, barium, calcium and strontium and forms an unstable blue solution. This solution contains the metal ion and free electrons that slowly decompose, release hydrogen and form the metal amide. Compared to water, liquid ammonia is less likely to release protons (H+ ions), is more likely to take up protons (to form NH4+ ions) and is a stronger reducing agent219. 

The Group 1A metals are extremely soluble in liquid ammonia, releasing hydrogen gas on dissolution. As the metal begins to dissolve, a deep blue solution forms. The color is attributed to the presence of solvated electrons, or e(NH3)r". The metal amide (MNH2) can be isolated by allowing the ammonia to evaporate. 

Liquid ammonia (b.p. -33°C) is a solvent which is not encountered frequendy, but which does have several important general uses, in particular dissolving metal reductions ("Birch" type reductions) and most reactions involving lithium amide or sodium amide as bases. Ammonia gas from a cylinder is condensed directly into the flask (Fig. 14.5). 

Many other examples of chemoselective enone reduction in the presence of other reducible functionalities have been reported. For instance, the C—S bonds of many sulfides and thioketals are readily cleaved by dissolving metals. " Yet, there are examples of conjugate reduction of enones in the presence of a thioalkyl ether group." " Selective enone reduction in the presence of a reducible nitrile group was illustrated with another steroidal enone. While carboxylic acids, because of salt formation, are not reduced by dissolving metals, esters" and amides are easily reduced to saturated alcohols and aldehydes or alcohols, respectively. However, metal-ammonia reduction of enones is faster than that of either esters or amides. This allows selective enone reduction in the presence of esters"" and amides - -" using short reaction times and limited amounts of lithium in ammonia. 

Extension of the dissolving metal reduction of enones to a,[3-unsaturated carboxylic acid esters converts the ester moiety to an amide. However, a, 3-unsaturat-ed esters undergo double bond reduction on treatment with magnesium in methanol. ... 

Na or Li and ammonia, excellent yields. This is a very good method to remove a benzyl group from an amide and will usually work when hydrogenolysis does not. A dissolving metal reduction can be effected without cleavage of a sulfur-carbon bond. Note also the unusual selectivity in the cleavage illustrated below. This was attributed to steric compression. Primary benzyl amides are not cleaved under these conditions. ... 

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