M.Sc Thesis

M.Sc StudentTsoglin Alexander
SubjectDevelopment of Mass Spectyrometric Methods for Analysis of
Novel Nitramine and Cyclic Peroxide Explosives
DepartmentDepartment of Chemistry
Supervisors PROF. Amnon Stanger
DR. Chagit Denekamp
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


This thesis focuses on mass spectrometric analysis of a group of cyclic triperoxides (CTP) and two nitramine explosives, Hexanitrohexaazaisowurzitane (HNIW) and 4,10-Dinitro-2,6,8,12-Tetraoxa-4,10-Diazaisowurzitane (DTIW). The goal of this research is to develop mass spectrometric methods for the identification of the above explosives and to understand their fragmentation pathways in the gas phase. Firstly, the optimal parameters for the analysis of the explosives were found, including the introduction/ionization methods. The most suitable introduction/ionization methods for the analysis of HNIW were found to be LC/ESI in the negative mode, by producing an anionic complexes via interaction of HNIW with inorganic anions. DTIW was analyzed successfully using a direct or GC introduction with positive CI/MS only. MS analyses of CTP were performed using LC-ESI/MS in positive ionization mode with addition of an ammonium salt, as a source of ammonium cation to produce a [CTP+NH4]+ complexes. In addition, it was found that Triacetone Triperoxide and Cyclohexanone Triperoxide can exist in two conformations at ambient temperature. This fact was proved by solving the crystal structure of the latter and supported by DFT calculations and chromatography-mass spectrometry analysis of both peroxides. Secondly, the gas phase fragmentation pathways of the explosives and their complexes were studied by CID experiments. For this purpose several methods of activation, dissociation and detection were used and proposed mechanisms were supported by DFT calculations and isotopic labelling of the studied explosives and the adduct ions. Thus, the main fragmentation in CID of DTIW is the loss of nitrous acid. The fragmentation pathways of HNIW depend on the activation/dissociation method and on the complexing anion. In order to understand these pathways, HNIW with two 15NO2 functional groups was synthesized and analyzed by CID. In addition, the structures of HNIW complexes with bromide and chloride were calculated. The calculations showed that the anions interact preferentially with two of the four identical hydrogen atoms of HNIW molecule and the geometry of the complex depends on the attached anion. This might explain the differences in dissociation pathways that involve the isowurzitane structure. The identities of [CTP+NH4]+ fragments in CID experiments and the routes for their formation were confirmed using deuterated ammonium addition along with deuterated CTP. It was found that all CTPs fragment in a similar pattern, producing two major and two minor daughter-ions. These fragmentation pathways could be used in analytical and forensic work for identification of the cyclic triperoxides.