Safety hydrogen azide

SAFETY PROFILE Confirmed human carcinogen. Hydrolysis reaction in the presence of moisture forms the explosive hydrogen azide gas. When heated to decomposition it emits toxic fumes of Cd and NOx. See also CADMIUM COMPOUNDS and AZIDES. 

CAUTION As with all azides of low molecular weight, tert-butyl azidoformate is sensitive to both heat (>80°C) and shockJ l It is usually purified by distillation under reduced pressure and detonation under these conditions has been reported (distillate and distillation residue are prone to explode). All operations involving this reagent should be carried out with great caution in a fume hood and behind a safety shield Hydrogen azide is an ichthyotoxic compound. 

N.B. A number of serious accidents have occurred due to spontaneous explosion of organic azides. Statements in the literature about the supposed stability of individual azides, particularly those of low molecular weight, should not be implicitly trusted (see, for example, Grundmann and Haldenwanger660). All operations with azides must be carried out with extreme care and with safety precautions similar to those used in work with peroxides, as described on page 306. Particular attention is directed also to the toxicity of hydrogen azide (hydrazoic acid). 

Hydrogen azide, HN3, and its salts (metal azides) are unstable substances used in detonators for high explosives. Sodium azide, NaNs, is used in air-bag safety systems in automobiles (see page 212). A reference source lists the following data for HN3. (The subscripts a, b, and c distinguish the three N atoms from one another.) Bond lengths Ng—Nt, = 124 pm Nb—Nc = 113 pm. Bond angles H—Na—Nb = 112.7° N —Nb—Nc = 180°. 

Caution. Although we have carried out this preparation without incident several times, copper azides, which are explosive, are intermediates in this reaction. This preparation should be conducted behind a safety shield. Pure 1,1 -diazidoferrocene has been reported to explode when heated rapidly above its melting point o/56°C. ° We strongly recommend carrying out the hydrogenation of l,r-diazidoferrocene without isolating it from its ether solutions. 

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