Electron ionization mass spectra of alkylated sulfabenzamides.

Mono-, di- and trialkyl derivatives of 'sulfabenzamide' (N-4-aminophenylsulfonylbenzamide) have been prepared and their electron ionization (EI) mass spectra examined. It is found that the fragmentation of N-alkylsulfabenzamides (alkyl = CH(3) to n-C(5)H(11)) proceeds via a very specific rearrangement process. The proposed mechanism involves an intermediate formation of distonic molecular ions, and the driving force for this process is the formation of stable N-alkylphenylcyanide cations [R-N(+)≡CC(6)H(5)]. The findings are confirmed by exact mass measurements, tandem mass spectrometry (MS/MS) experiments and deuterium labeling.