Rapid degradation of cyclic peroxides by titanium and antimony chlorides

Abstract

First responders face extraordinary risks when dealing with organic peroxides such as TATP due to the extreme sensitivity of this class of explosives, and to a lack of a robust chemical means of safe and rapid neutralisation. The Lewis acids TiCl₄ and SbCl₃ have been found to demonstrate a novel degradation mechanism, with TiCl₄ degrading a model cyclic peroxide in minutes when used in a two-fold excess, or ∼3 hours at half equivalence. The products cannot re-form peroxide compounds as is the case with acid degradation, suggesting the two mechanisms are fundamentally different. The Lewis acids mediate a rearrangement reaction in the cyclic peroxide backbone leading to relatively innocuous products through deactivation of oxidising O. Sub-stoichiometric TiCl₄ reactions highlight a secondary reaction pathway that also leads to some oxidative chlorination products, possibly mediated by an unconfirmed titanium-oxychloride species. SbCl₃ was found to exhibit similar reactivity to TiCl₄, although at a slower rate. A mechanism is proposed, consistent with the observations for both stoichiometric and sub-stoichiometric quantities of TiCl₄.