Metal-in-Ammonia Solutions

Although agreement among workers in the field is not complete, it now appears that the predominant species in concentrated solution is the solvated Na2 molecule with the two 3a electrons delocalized over a number of surrounding solvent molecules, but still paired. The blue species is probably an ammoniated electron—that is, the electride ion.  

Careful evaporation of such solutions yields the original alkali metal. If a catalytic amount of an oxidizing agent (for example, FeCl or I2) is added, however, hydrogen gas is evolved, and the alkali-metal amide MNH2, is formed. Such a compound contains the strongly basic NH ion, and reacts with water to give NHS and OH  

The alkaline-earth metals and certain of the rare earths dissolve in ammonia more slowly, but the resulting solutions are similar to those for 

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Reduction of suitably oriented 1,3-diketones by alkali metal in ammonia solutions also generates reactive nucleophilic intermediates which are capable of intra- and intermolecular attack on electrophilic functions. 

Carbonyl groups can be reduced by sonication using metal and THE Thus camphor on sonication in THF gives a mixture of endo and exo bomeol in the same ratio as by using metal in ammonia solution (Scheme 17). 

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