Hydrogen Azide, Anhydrous

Anhydrous hydrogen azide was first prepd in 1891 by Curtius Radenhausen by fractionally distilling the aq soln with fused calcium chloride(Ref 4). In 1907 Dennis ... 

Aqueous solutions of hydrogen azide are readily obtained by treatment of sodium azide f with sulfuric acid. Since pure hydrogen azide is extremely explosive, and since its vapors produce most unpleasant physiological effects, it is advisable to use care in its preparation. Especially is the treatment of dry sodium azide, or of a cold solution, with sulfuric acid to be avoided, since this results in the formation of pure hydrogen azide (b. 37°C.) which may condense to the anhydrous liquid or to a highly concentrated aqueous solution, both of which are extremely explosive. 

Sodium hydrogen carbonate, sodium carbonate, ammonium hydrogen carbonate, anhydrous sodium sulfate, and sodium azide were purchased from Fisher Scientific. 

Anhydrous hydrogen azide was first prepd in 1891 by Curtius Radenhausen by fractionally distilling the aq soln with fused calcium chloride(Ref 4). In 1907 Dennis 6c Isham isolated the pure compd in larger quanty and detd some physical and chem props (Ref 18). The pure compd is extremely expl but it can be kept for days at RT in sealed... 

Dicyanodiamide reacts particularly readily with azides, giving 5-amino-tetrazoles.50 The parent compound is obtained analogously in about 80% yield by heating an alcoholic solution of hydrogen azide with anhydrous hydrogen cyanide at 100° for 2-3 days.52... 

A solution of hydrogen azide in ether is prepared as described previously. Fifty milliliters of this solution is diluted to 500 ml. with anhydrous ethyl ether and cooled in an ice-salt mixture. Pure, dry ammonia gas is slowly bubbled through this solution until precipitation is complete. This operation should be carried out in a well-ventilated hood. The precipitated ammonium azide is filtered and stored in a vacuum desiccator, which from time to time is alternately evacuated and filled with dry air, until the ether has completely evaporated. Yield 4.1 g. (74 per cent). The product is of a high degree of purity. 

The most important method of preparation of hydrogen azide is by passing nitrous oxide gas into fused sodamide at 190° C under anhydrous conditions. 

Anhydrous hydrogen azide is obtained by dropping 2 1 sulphuric acid on dry potassium azide. 

Bamberger-type rearrangements320 carried out in anhydrous hydrogen fluoride allow the synthesis of 4-fluoroaniline derivatives from ALarylhydroxylamines321 322 or aryl azides.50 Examples of the synthesis of 4-fluoroanilines 11 from (V-arylhydroxylamines 10 are given below.322... 

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