Explosiveness of 4-azidobenzaldehyde

Paul M. Lahti
University of Massachusetts, Amherst

Chemical & Engineering News (13 Jul 1998) Vol. 76, No. 28, pp. 8.

In a recent edition of Synthetic Communications, we described a convenient synthesis of multigram amounts of 4-azidobenzaldehyde [Synth. Comm., 28, 1087 (1998)], a compound that is also commercially available. We experienced no difficulty in making approximately 10-g lots of this compound, although we took normal precautions in making such a molecule (blast shield, shielding from light and heat). The Material Safety Data Sheet (MSDS) available to us from TCI America, a commercial provider of this compound, did not describe potential detonation or shock sensitivity.

However, after publication of our article, scientists at Dow Chemical's Advanced Materials Electronics Laboratory made us aware of data describing a considerable shock sensitivity hazard for 4-azidobenzaldehyde. They note that U.S. patent 4,354,976, column 1, lines 35-40, states that "4-azidobenzaldehyde is an exceptionally explosive substance." Dow scientists tested the shock sensitivity of this material by a drop weight impact test as outlined in ASTM Test Method D2540.

The test result was positive, with an H50 value of about 11 kg-cm. The evidence for a positive test was conversion of the liquid sample to a solid char with gas generation. These scientists communicated their concern that 4-azidobenzaldehyde is too shock sensitive to be isolated in other than very small quantities.

Accordingly, we most strongly recommend that the greatest of precautions be observed in using our synthesis or any other preparation of 4-azidobenzaldehyde, despite apparent lack of MSDS shock sensitivity warnings, and despite the lack of incident observed by us in our methodology. For example, the compound may be best manipulated as a dilute solution, rather than in neat form.

We thank Dow Chemical for making us aware of these data from their lab and from other sources.

TCI America responds:

We thank Lahti for bringing this potential hazard to our attention. We have since updated our MSDS for 4-azidobenzaldehyde, and we encourage anyone who has an old TCI America MSDS to update it accordingly.

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