Intramolecular oxygen transfer in the gas-phase dissociation of protonated sulfonamides

Abstract In this study, an intriguing intramolecular oxygen transfer reaction in the gas-phase dissociation of protonated sulfonamides was investigated by electrospray ionization tandem mass spectrometry (ESI-MS n ). Sulfonamides with various substituent groups (R) were chosen for collision induced dissociation (CID) experiments, and a peak of a characteristic phenoxonium ion (RC 6 H 4 O + ) was observed for the sulfonamides with substituent groups that favor the formation of conjugated phenoxonium ions. A mechanism involving a three-membered ring transition state (TS1) was proposed for the generation of this fragment ion, which was supported by DFT calculations. And also, the ratio of intensity of I R C 6 H 4 O + and I ( R C 6 H 4 + + R C 6 H 4 O + ) correlates well with the Hammett para-substituent constants of substituent groups. Our work deepens the understanding of the intramolecular oxygen transfer reactions of sulfonamides in the gas phase.