Study of the mass spectral fragmentation processes in dinitroquinoxalines using tandem methodologies

Following electron ionization, the fragmentations of isomeric dinitroquinox alines have been investigated making use of tandem mass spectrometry method ologies such as collisional activation (CA), various linked-scanning (LS) e xperiments, and mass-analyzed ion kinetic energy (MIKE) spectrometry, It wa s shown that, for the two ortho-dinitroquinoxalines 1 and 2, the most abund ant fragment ion at m/z 116 is generated for 1 by successive losses of NO2. , CO, and NO., whereas for 2, it is the result of two main competing fragme ntation routes. The fragmentation of the meta-dinitroquinoxaline 3 differs significantly as an abundant and quite characteristic ion at m/z 127 is the result of consecutive eliminations of NO2. and HNO2. Substitution of the p yrazine ring (for example, compounds 4 and 5) or of the benzene ring (for e xample, compounds 6 and 7) strongly modifies the reactivity.