On November 21, 2019, at approximately 2:00 AM, in Halifax, Nova Scotia, Halifax Regional Police carried out a controlled detonation of a bottle
outside an apartment building. (1) The bottle originally contained 500 mL of Life brand 99% isopropyl alcohol (rubbing alcohol, 2-propanol), with an
expiry date of February 2007, and was stored in the dark underneath a bathroom sink. In August of 2017, and again in May 2019, application of the
rubbing alcohol to sterilize an area of skin (on two different people) resulted in scab formation, thought originally to be a sensitivity to rubbing
alcohol. Some time after May 2019, the bottle had tipped over, cracking the plastic top and partially spilling the contents, which were slower to
volatilize than expected for pure rubbing alcohol, and whose odor was a little off. In mid-November, 2019, the owner partially discarded some of the
remaining liquid, and at this time noticed gas evolution at the sink drain and the presence of approximately 25 g of a white solid mass remaining in
the bottle. The owner initially thought that it might have been a result of product tampering, so a small sample of the solid was analyzed by X-ray
crystallography (2) and found to be a polymorph (3) of triacetone triperoxide (TATP), an organic peroxide and high explosive. Once the solid compound
was identified as such, emergency services were called to handle the disposal at the apartment building.
The ability of 2-propanol to form peroxides has been mentioned before. (4) The exact nature of the solid peroxide formed has not been known until now.
Stoichiometrically, 2-propanol and oxygen gas is equivalent to acetone and hydrogen peroxide, the ingredients required for classic TATP synthesis, (5)
which may be relevant to its formation under these conditions. Similar compounds are known to form upon photosensitization with benzophenone. (6)
Given the use of 2-propanol in clandestine drug laboratories and of TATP in recent terrorism incidents, the implications for police work are clear.
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