Ammonium Fonnate

Oxazole synthesis from benzoin and nitrHes or ammonium fonnate. 

Cyclization of 382 to Af-cyclohexyl-2-(2 -chlorophenyl)-4-phenyl-5-oxazolecar-boxamide 383 was accomplished using ammonium fonnate in refluxing acetic acid. Selected examples of iV-cyclohexyl-2,4-diaryl-5-oxazolecarboxamides 383 are shown in Table 1.31. 

Table 16-21 Recommended Composition Range for Copper-Ammonium Fonnate Solutions ...

Figure C2.12.2. Fonnation of Br0nsted acid sites in zeolites. Aqueous exchange of cation M witli an ammonium salt yields tlie ammonium fonn of tlie zeolite. Upon tliennal decomposition ammonia is released and tire proton remains as charge-balancing species. Direct ion-exchange of M witli acidic solutions is feasible for high-silica zeolites.

In base the tetrahedral intennediate is fonned in a manner analogous to that proposed for ester saponification. Steps 1 and 2 in Figure 20.8 show the fonnation of the tetrahedral intennediate in the basic hydrolysis of amides. In step 3 the basic amino group of the tetrahedral intennediate abstracts a proton from water, and in step 4 the derived ammonium ion dissociates. Conversion of the carboxylic acid to its conesponding carboxylate anion in step 5 completes the process and renders the overall reaction ineversible. 

Hydrofluoric acid dissolves the nitride slowly with fonnation ammonium fluoborate thus —... 

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