- Rapid degradation of cyclic peroxides by titanium and antimony chlorides
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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.
- Bali, Mark S.,Armitt, David,Wallace, Lynne,Day, Anthony I.
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p. 6775 - 6783
(2015/04/14)
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- Evidence for the Three-Center Elimination of HCl from CH3CHClO
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Time-resolved IR spectral photography and transient diode laser absorption measurements reveal a yield of HCl from the photolysis of Cl2 in the presence of C2H5Cl and O2 which is 78percent larger than expected from Cl + C2H5Cl.The HCl formation occurs in two steps: a rapid rise to = 0, followed by a secondary rise to = 1.780 with a rate constant of k3 = (5.2 +/- 1.3)E-12 cm3s-1.In the presence of NO, the rate of secondary HCl formation is greatly enhanced, but its yield (84percent) is comparable to that in the absence of NO.The secondary HCl is explained as an elimination product from the CH3CHClO, which can be generated by the reaction of CH3CHClO2 with itself of with NO.The fact that the secondary HCl yield increases by 12percent when using CD3CH2Cl shows that the secondary HCl is formed mainly by three-center elimination from the 1-chloroethoxy radical.We also report UV absorption cross sections for CH3CHClO2, which has a broad maximum of ?max = 0.029 Angstroem2 from 215 to 248 nm, and CH2ClCH2O2, with ?max = 0.045 Angstroem2 at 240 nm.The self-reaction rate constants are (5.2 +/- 1.3)E-12 cm3s-1 and (6.0 +/- 0.8)E-12 cm3s-1, respectively.Finally, the rate constant for the reaction Cl + C2H5Cl = C2H4Cl + HCl (1) is determined to be k10 = (7.3 +/- 0.9)E-12 cm-3s-1.
- Maricq, M. Matti,Shi, Jichun,Szente, Joseph J.,Rimai, L.,Kaiser, E. W.
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p. 9686 - 9694
(2007/10/02)
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