Methane Activation by Metal-Free Radical Cations: Experimental Insight into the Reaction Intermediate

An experimental insight into the reaction intermediate of methane activation by metal-free radical cations (SO2+) was studied. The [CH4-SO2+].+ intermediate was obtained instead by SO2/CH4 high pressure chemical ionization performed in a high sensitivity double focusing mass spectrometer. he low yield requires both high sensitivity and high resolution, since isobaric peaks are found at the same nominal weight of m/z 80. The [CH4-SO2+].+ ion was mass selected and submitted to structural assay by CAD mass spectrometry. The high resolution CAD spectrum shows that the ionic population does not contain a [SO 2+-CH4].+ ion-molecule complex. Fragments such as m/z 31 (C,H3,O)+ and 63 (C,H 3,S,O)+ indicate that the ion explores strongly bound structures along the energy surface and raise the question of whether the methyl group is bound to the oxygen or sulfur atom.