Azide explosions discussed

Peter G. Urben
Editor, "Bretherick's Handbook of Reactive Chemical Hazards", Kenilworth, Warwickshire, England

Chemical & Engineering News (13 Dec 1993) Vol. 71, No. 50, pp. 4.

There is every reason to suppose that eschewing halogenated solvents will not eliminate azide explosions such as those reported by N. P. Peat and P. M. Weintraub (C&EN, April 19, page 4) and by Victor J. Hruby, Lakmal Boteju, and Guigen Li (C&EN, Oct. 11, page 2). The first group explicitly combined sodium azide and sulfuric acid, generating hydrogen azide, which is very explosive. The second group's report was less explicit, but the cold traps of the vacuum pump of the rotary evaporator were involved, implying an explosive more volatile than dichloromethane.

Hydrogen azide (boiling point 37 C) fits this description. The boiling point of diazidomethane may be known, but not to me; I should expect it to be at least 90 C. This means explosions late in solvent stripping, either in the evaporating flask or in the condenser. On the evidence offered your readers, there is no reason to postulate the complicated reaction leading to diazidomethane, even though it can occur in other circumstances.

Hydrogen azide is also, of course, extremely toxic, and it is a rare explosion that consumes all the explosive, rather than spraying it around.

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