Negative-ion mass spectra of sulfonamides

An example of structural discrimination was found in the mass spectra of isomeric N-nitrophenyl benzenesulfonamides 11781. Common features of the mass spectra of ortho, meta and para isomers were the presence of [M — H]- ions, more intense than the molecular anion, and the presence of fragments at m/z 137 and m/z 141, originating from N—S bond rupture. However, the ratio of the intensities of the latter ions was markedly higher for the ortho and para compounds, which reflected the stabilization of the m/z 137 anion by a nitro group in a conjugatively effective relationship. The ortho isomer was further differentiated by the elimination of hydroxyl radical, to form [M — OH] - ions. 

The [ArS02] ions, produced by dissociative secondary electron capture from sulfonamides 103c and 103d, dissociated both by simple cleavage (equation 35a-d) and by rearrangement (equation 35e) processes, as shown by their CAD MIKE spectra83. 

Bowie and coworkers84 have reported the kinetic energy releases for metastable negative-ion decomposition of p-nitrobenzenesulfonamide 118c. The simple cleavage process 

However, caution was necessary to assess the unimolecular rather than collision-induced character of these consecutive metastable reactions85. 

SIMS15 and atmospheric-pressure ion evaporation MS16 have found application for the production of negative ions, [M — H], or ion clusters, [M - H + (H20)J, from biologically important sulfonamides. 

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