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Nitramine anion fragmentation: a mass spectrometric and Ab initio study
Jan Florián1, Lan Gao, Vladimir Zhukhovskyy
1Department of Chemistry, Loyola University, Chicago, Illinois 60626, USA.
Journal of the American Society for Mass Spectrometry
|February 24, 2007
Summary
This study investigates fragmentation mechanisms of RDX and its metabolites using NCI GC/MS. Key findings reveal dominant fragment ions (m/z 86, 102) formed by specific bond cleavages and neutral losses.
Area of Science:
- Analytical Chemistry
- Computational Chemistry
- Mass Spectrometry
Background:
- Hexahydro-1,3,5-trinitrotriazine (RDX) and its nitroso metabolites are compounds of interest.
- Understanding their fragmentation patterns in mass spectrometry is crucial for identification and analysis.
Purpose of the Study:
- To elucidate the fragment ion formation mechanisms of RDX and its nitroso metabolites.
- To identify the structures of abundant fragment ions observed in negative chemical ionization (NCI) mass spectra.
- To computationally validate proposed fragmentation pathways.
Main Methods:
- Gas chromatography-mass spectrometry (GC/MS) with negative chemical ionization (NCI).
- Ab initio and density functional theory (DFT) calculations.
- Analysis of isotope-labeled standards.
Main Results:
- NCI mass spectra are dominated by ions from nitrogen-nitrogen and carbon-nitrogen bond cleavage within the triazine ring.
- The most abundant fragment ions observed are m/z 86 (C2H4N3O) and m/z 102 (C2H4N3O2).
- Isotope labeling confirms these ions result from neutral losses involving two exocyclic nitrogens and one ring nitrogen.
Conclusions:
- The primary fragment ions (m/z 86 and 102) are formed via single fragmentation reactions from (M--NO)(-) or (M--NO2)(-) anions.
- These reactions involve specific neutral losses (CH2N2O or CH2N2O2), rather than sequential losses of HNO2, HNO, or HCN.
- Computational analysis supports the proposed fragmentation mechanisms and ion structures.
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