Preparation of 1,5-Diamino-1H-tetrazole

Michael A. Hiskey
Los Alamos, N.M.

Chemical & Engineering News (25 Jul 2005) Vol. 83, No. 30, p.p. 5-6.

We recently had an unanticipated explosion resulting in the injury of two chemists. The workers were repeating a recently published preparation of 1,5-diamino-1H-tetrazole by the aqueous diazotization of diaminoguanidine hydrochloride using a single equivalent of nitrous acid (Inorg. Chem. 2005, 44, 4237). After neutralization (pH 8) and evaporation, the desired product is extracted from the inorganic salts with hot ethanol. The ethanol is then evaporated and the resulting solid recrystallized from water. The preparation states that the product is pure after the ethanol extraction. Unfortunately, we have found that the ethanol extracts not only the desired product but also a very sensitive side product, 5-azidotetrazole. This side product is produced by either double diazotization of diaminoguanidine or possibly by diazotization of the desired product through the intermediate 1H-tetrazolo[1,5-d]tetrazole. If this procedure is repeated, it is imperative that the ethanol extract not be taken to dryness.

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