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Collison‐induced dissociation and photodissociation of nitroaromatic molecular ions: A unique isomerization for p ‐nitrotoluene and p ‐ethylnitrobenzene ions
Author(s) -
Cassady Carolyn J.,
McElvany Stephen W.
Publication year - 1993
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210281242
Subject(s) - isomerization , chemistry , dissociation (chemistry) , ion , photodissociation , photochemistry , fourier transform ion cyclotron resonance , mass spectrometry , molecule , mass spectrum , collision induced dissociation , tandem mass spectrometry , organic chemistry , chromatography , catalysis
The photodissociation and low‐energy collision‐induced dissociation of p ‐nitrotoluene and p ‐ethylnitrobenzene molecular ions were studied using Fourier transform ion cyclotron resonance mass spectrometry. The dissociation of these ions is highly dependent on the time‐scale of the experiment and the pressure of the nitroaromatic compound. Collisions of the ions with nitroaromatic neutral species increase the abundance of fragment ions due to NO elimination, while collisions with inert gases such as sulfur hexafluoride and argon have no effect. Evidence is presented for the occurrence of an ion–molecule reaction between p ‐alkylnitrobenzene ions and nitroaromatic neutral species that induces isomerization of the ion. This isomerization is proposed to involve a nitro‐to‐nitrite rearrangement. Although the mechanism of this process is unknown, isotopic labeling experiments have shown that it does not involve nitrogen atom transfer between the two reactants. The dissociations of o ‐nitrotoluene, m ‐nitrotoluene and nitrobenzene ions are also discussed. For these ions, no pressure‐ or time‐scale‐dependent behavior was observed, indicating that an isomerization did not occur.