RDX (1,3,5-trinitroperhydro-1,3,5-triazine), an explosive cyclic nitramine, is used for both military and industrial applications. Fragmentation mechanisms of RDX under negative chemical ionization mass spectrometry (NCI-MS) were studied by density functional theoretical (DFT) methods at B3LYP/6-311G(d,p) level of theory. B3PW91, O3LYP, and X3LYP functionals were used to evaluate the B3LYP results; also, basis sets effects were studied using 6-311++G (d, p). The goal was to study the energetics and ion structures along the fragmentation pathways. The following RDX conformations were modeled: AAA, AAE, AEE, and EEE (A=axial and E=equatorial). The results showed the anion-molecule complex of RDX as the energetically favored structure. The calculations showed the importance of conformational analysis in understanding the associated RDX fragmentation mechanisms. For HNO2 elimination, NO2 group at an axial position led to a different transition state than NO2 at an equatorial position. Both cyclic and acyclic ion structures were considered along the pathways.

Theoretical studies of negative chemical ionization mass spectrometric fragmentation mechanisms of RDX

244th National Meeting (2012)

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