Successful STR amplification of post-blast IED samples by fluorescent visualisation and direct PCR.

Improvised explosive devices (IEDs) present a number of challenges in terms of the generation of forensically relevant information. Inhibition to PCR from sub-optimal sample types as well as from specific substrates has historically meant that extraction prior to PCR has been required. Improvements to STR kit buffers lead to the successful introduction of direct PCR to the analysis of IED-relevant samples, however none of these samples have been exposed to detonations. This study presents data to support the use of direct PCR in the analysis of IED components post-detonation. VeriFiler™ Plus generated informative profiles, containing ≥ 12 autosomal alleles, from samples touched for a maximum of 15 s that were then exposed to a detonation from plastic explosive placed as close as 100 mm. Of the 37 recovered touched items or fragments, 28 contained autosomal alleles from the donor with 18 (49 %) presenting informative profiles that matched the DNA donor. This compared with results following STR PCR post-extraction with one of 11 amplified post-detonation touch DNA samples being informative. The use of Diamond™ Nucleic Acid Dye (DD) staining and visualisation before and after detonation allowed for analysis as to cell loss or damage as a result of the detonation itself and aided in the triaging of samples to be selected for DNA profiling. This is the first record of cellular visualisation and comparison before and after detonation with accompanying STR results on a range of sample types typical of IED constituents. Following comparison of DD visualised cells and STR amplification success, chemical analysis of plastic and electrical tape samples supported substrate-specific inhibition. These data represent the first instance of informative DNA profiles being produced from post-detonation samples using direct PCR, as close as 100 mm from the charge.

Rapid degradation of cyclic peroxides by titanium and antimony chlorides.

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.

Confirmation of the molecular structure of tetramethylene diperoxide dicarbamide (TMDD) and its sensitiveness properties.

Conjecture existed as to the molecular structure of the crystalline organic peroxide reaction product derived from the acidified aqueous mixture of urea, formaldehyde, and hydrogen peroxide. This study used X-ray crystal structure determination to unequivocally define the reaction product as the 14-membered ring structure tetramethylene diperoxide dicarbamide (TMDD). Crystals of TMDD belong to the monoclinic space group Pc, a = 4.587(4), b = 16.080(2), c = 6.690(5) Å, ß = 107.44(5)°. The crystal contains one crystallographically independent molecule with approximate Cs symmetry. Intramolecular π-stacking of the carbonyl groups is a feature, while intermolecular H-bonding between the N-H and C═O functionalities affords linear polymeric strands that is associated with the extremely fine needle crystal morphology that necessitated synchrotron radiation for the structure determination. Sensitiveness testing examining susceptibility to initiate due to heat, impact, friction, and electrostatic stimuli was conducted to gauge the hazards associated with the material. It was revealed to be a primary explosive, particularly susceptible to impact initiation.

Cyclic pentanone peroxide: sensitiveness and suitability as a model for triacetone triperoxide.

Research to counter the threat of organic peroxides such as triacetone triperoxide (TATP) is at times hampered by their inherent extreme sensitiveness and volatility. This work describes an approach to lowering some risks associated with the handling of TATP in the laboratory through the use of an analog species, tripentanone triperoxide (TPTP). Sensitiveness has been tested via standard methods. GCMS analysis has shown that TPTP degrades via similar mechanisms to TATP under a range of conditions. Slight differences in product composition were traced to side reactions which may also affect impurities present in homemade TATP synthesis. A pilot field trial was conducted to evaluate TPTP as a substitute for TATP in explosive detection dog (EDD) scent training. The degradation studies have yielded insights into the complexities of the acidic degradation of cyclic peroxides with potential forensic application, and TPTP's inadequacy as a TATP pseudoscent is a valuable example of the limitations of such training aids.

Gas chromatography/mass spectrometry analysis of triacetone triperoxide (TATP) degradation products.

Interest in the analysis and detection of triacetone triperoxide (TATP) and other organic peroxides has increased in recent years. Also of interest is the degradation and decomposition of the peroxides, not only to gain more detailed chemical information from organic peroxide samples, but also to investigate possible new procedures or mechanisms for chemical neutralisation. This report investigates the chemical degradation products of TATP after it has been treated with different acids within a sealed system over a period of 14 days. The samples were collected and analysed by solid-phase microextraction (SPME) and direct liquid injection gas chromatography/mass spectrometry (GC/MS). The results of the experiments indicate that the rate of chemical degradation of TATP and the products formed are dependent on the type of acid. The observed differences enables the type of acid used in the degradation process to be determined, provide complementary information to identify the presence of TATP, and possibly indicate new pathways that may be used to chemically neutralise TATP.

Some transition metal complexes derived from mono- and di-ethynyl perfluorobenzenes.

Transition metal alkynyl complexes containing perfluoroaryl groups have been prepared directly from trimethylsilyl-protected mono- and di-ethynyl perfluoroarenes by simple desilylation/metallation reaction sequences. Reactions between Me(3)SiC[triple bond, length as m-dash]CC(6)F(5) and RuCl(dppe)Cp' [Cp' = Cp, Cp*] in the presence of KF in MeOH give the monoruthenium complexes Ru(C[triple bond, length as m-dash]CC(6)F(5))(dppe)Cp' [Cp' = Cp (); Cp* ()], which are related to the known compound Ru(C[triple bond, length as m-dash]CC(6)F(5))(PPh(3))(2)Cp (). Treatment of Me(3)SiC[triple bond, length as m-dash]CC(6)F(5) with Pt(2)(mu-dppm)(2)Cl(2) in the presence of NaOMe in MeOH gave the bis(alkynyl) complex Pt(2)(mu-dppm)(2)(C[triple bond, length as m-dash]CC(6)F(5))(2) (). The Pd(0)/Cu(i)-catalysed reactions between Au(C[triple bond, length as m-dash]CC(6)F(5))(PPh(3)) and Mo( identical withCBr)(CO)(2)Tp* [Tp* = hydridotris(3.5-dimethylpyrazoyl)borate], Co(3)(mu(3)-CBr)(mu-dppm)(CO)(7) or IC[triple bond, length as m-dash]CFc [Fc = (eta(5)-C(5)H(4))FeCp] afford Mo( identical withCC[triple bond, length as m-dash]CC(6)F(5))(CO)(2)Tp* (), Co(3)(mu(3)-CC[triple bond, length as m-dash]CC(6)F(5))(mu-dppm)(CO)(7) () and FcC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC(6)F(5) (), respectively. The diruthenium complexes 1,4-{Cp'(PP)RuC[triple bond, length as m-dash]C}(2)C(6)F(4) [(PP)Cp' = (PPh(3))(2)Cp (); (dppe)Cp (); (dppe)Cp* ()] are prepared from 1,4-(Me(3)SiC[triple bond, length as m-dash]C)(2)C(6)F(4) in a manner similar to that described for the monoruthenium complexes -. The non-fluorinated complexes 1,4-{Cp'(PP)RuC[triple bond, length as m-dash]C}(2)C(6)H(4) [(PP)Cp' = (PPh(3))(2)Cp (); (dppe)Cp (); (dppe)Cp* ()], prepared for comparison, are obtained from 1,4-(Me(3)SiC[triple bond, length as m-dash]C)(2)C(6)H(4). Spectro-electrochemical studies of the ruthenium aryl and arylene alkynyl complexes - and -, together with DFT-based computational studies on suitable model systems, indicate that perfluorination of the aromatic ring has little effect on the electronic structures of these compounds, and that the frontier orbitals have appreciable diethynylphenylene character. Molecular structure determinations are reported for the fluoroaromatic complexes , , , and .

Synthesis and optical properties of bis(oligophenyleneethynylenes).

Bis(oligophenyleneethynylenes) 1-4 were prepared as representative members of a new class of potential nonlinear optical materials. The optical properties of 1-4 were examined for evidence of restricted rotation of the aryl rings when compared to their single-strand precursors, which could potentially increase their nonlinear response through more effective conjugation. The effect of altering the electron density of the terminating functional group of these compounds on their properties was also investigated.