3-Phenyl-2-phenylsulfonyl-oxaziridine stability

Mark Marlatt and Mark Lovdahl
Pfizer Global Research & Development

Chemical & Engineering News (25 Feb 2002) Vol. 80, No. 8, p. 4.

Over the past three to four years, we have been synthesizing and using 3-phenyl-2-phenylsulfonyl-oxaziridine here at Pfizer Global Research & Development, Ann Arbor, Mich. We followed an organic synthesis preparation [Org. Synth., 66, 203, (1988)] in which there is a warning of exothermic decomposition of this compound if stored at room temperature for as little as two weeks.

Although an extensive literature search was performed, no other reports were found discussing the potential dangers of this compound. Therefore we explored the thermal stability of the oxaziridine reagent. The results of the differential scanning calorimetry (DSC) and the accelerated rate calorimetry (ARC) both indicated a relatively slow, low-energy reaction followed by a very rapid, high-energy reaction. Consequently, we made it a habit to store the compound in a freezer at ???10 °C and, until the incident described below, we had no problems.

Recently, an odd substance was observed leaking out of a freezer. Upon investigation by the local HazMat team, it was found that a 1-kg batch of the oxaziridine stored in a plastic container had exothermically decomposed, blowing the cap off and burning the storage container. Although there were no injuries, the freezer was destroyed.

It is believed that the container had been removed from the freezer during routine laboratory use and allowed to stand at room temperature for an unknown period of time before being returned to the freezer. Although the DSC and ARC curves did not indicate any potential for autocatalytic decomposition, it is possible that the oxaziridine had converted to a less stable mixture during the time at room temperature. The lot in question was prepared less than two months prior to the incident and had been in the freezer for most of that time.

We recommend storing this compound in plastic rather than glass to avoid shrapnel if there is decomposition, storing the compound in a freezer (0 to ???10 °C), and returning unused material immediately to the freezer after routine laboratory use. We also feel it would be wise to split larger batches into smaller lots for storage, thereby minimizing the amount of material exposed to room temperature at any one time.

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