Influence of the substituent on the major decomposition channels of the NO2 group inpara-substituted nitrobenzenes: a tandem mass spectrometric study

Abstract

The relative extents of loss of NO 2 and NO were determined by 70 eV electron ionization and tandem mass spectrometry using B/E linked scans to investigate metastable (unimolecular) and collision-induced dissociation processes for molecular ions formed by electron ionization of para-substituted nitrobenzene compounds. The substituents used (NO 2 , CHO, H, OCH 3 ) represent a wide range of electron donor-acceptor properties. Loss of NO 2 was favored by electron-withdrawing groups, while an electron-donor group favored loss of NO. Ion fragmentation mechanisms are consistent with the hypothesis that NO 2 to ONO (nitro to nitrite) isomerization precedes the loss of NO. Ring fragmentation (loss of CO) was observed only after all of the electron-withdrawing groups had dissociated. while the electron-donor group OCH 3 remained attached to the ring in the analogous CO elimination. These results are placed in the context of the thermolysis behavior of nitroaromatic explosives.

Differentiation of isomeric dinitrotoluenes and aminodinitrotoluenes using electrospray high resolution mass spectrometry

“…These m / z 165 and m / z 152 fragment ions show a competition between the prompt isomerization of –NO 2 into –ONO leading to loss of NO • ( m / z 152), which is favored in comparison to the ‘ ortho effect’ hydrogen transfer leading to OH • release ( m / z 165, Table S3). Although the NO • loss, resulting from the NO 2 /ONO isomerization, has been observed in many other studies for radical anions, we show herein that this isomerization plays an important role during fragmentation of [M‐H] ‐ ions of nitrotoluenes.…”

Structure and Location of the Regulatory β Subunits in the (αβγδ)4 Phosphorylase Kinase Complex

“…Theoretical fragmentation of the conjugate in the positive mode was accomplished using the sequences for each peptide in the conjugate and the masses for each intervening chemical cross-link and its possible fragmentation products, using a mass error tolerance not exceeding 0.7 Da for each fragment ion. A modification table was generated for the DFDNB cross-linker based on the loss of NO 2 observed for structural analogs of the reagent (40,41). Potential matching ion assignments for each fragment mass generated by MS2Links were verified using a spreadsheet containing an array of masses predicted for the cross-linker (and fragments thereof) and also those generated for each peptide in the conjugate using MS Product, a fragmentation tool in Protein Prospector developed at the University of California, San Francisco (42).…”

Development of a QSPR model for predicting thermal stabilities of nitroaromatic compounds taking into account their decomposition mechanisms

“…In fact, a reliable model was more expected for the non-ortho than for the ortho molecules since many different reaction paths exist upon the nature of the substituent in ortho position from the nitro group (nitro, alcohol, amino…) [52] whereas all non-ortho nitroaromatic compounds follow the same decomposition process, C-NO 2 homolysis being evidenced in previous theoretical studies [60,61] as the main reaction path (without influence of the substituent nature in meta and para position to the nitro group). Besides the applicability domain analysis confirms this observation since the predictive power (R 2 in ) of models 2 (entire set) and 4 (ortho molecules) are low in their applicability domain, compared to the one of model 3 (non-ortho molecules).…”