Crystal alkali amides

Amides and related compounds have been thoroughly investigated as ligands for alkali metals. Studies in solution have been made using various physicochemical techniques these, and MO calculations, show that the interaction of amides with M+ is via the carbonyl function.56,57 This leads to a delocalization of the amide N electron pair and so it is possible to follow the decrease in C—O, and the increase in C—N, bond orders using IR spectroscopy. X-Ray crystal structures of amide complexes have shown both types of complexation interaction to be present (Table 2). 

Since most of the synthetically useful enolate anions described in the previous section are prepared by the reactions of enolizable substrates with alkali metal amide bases, it is appropriate to note a few structures of these amide bases. The common bases in synthetic organic chemistry include LDA and LHMDS. The structures of both of these bases are known as the THF solvates.Both of these compounds form bis-solvated dimers corresponding to structure (201). The diethyl ether solvate of LHMDS also forms a bis-solvated dimer (202).Sodium hexamethyldisilazide crystallizes as an unaggregated monomer from benzene solution.Two different cryst line forms of KHMDS are known as the polymeric dioxane solvate (203), ° and the unsolvated dimer (204). ... 

Benzenesulphonamide, C6H5SO2NH2, is formed by the action of ammonia on benzenesulphonyl chloride. It crystallizes from hot water in needles, which melt at 156°. It shows the chemical properties characteristic of amides. On account of the presence of the strongly negative C6H5SO2 group, the amide dissolves in aqueous solutions of alkalies. 

Ammeline and ammelide can be regarded as partial amides of cyanuric acid. They are acid and have no use in resin production. They are very undesirable by-products of the manufacture of melamine because of their catalytic effect in the subsequent MF resin production, due to their acidic nature. If present, both must be removed from crude melamine by an alkali wash and/or crystallization of the crude melamine. 

In case of zeolite crystallization it is vrorth mentioning that organic solvents have low solvent power for silica and alumina and compared to water will not help zeolitization (18). Water and alkali have good solvent power for the oxides mentioned. A valid alternative is liquid ammonia mixed eventually with amides. The necessary low handling temperature will, however, slow down nucleation and crystal growth (18). 

Kubota, K Matsumoto, H., Melting and Crystallization Behaviors of Alkali Metal (Fluorosulfonyl)(trifluoromethylsulfonyl)amides, Chem. Lett., 2011,40,1105-1106. 

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