Journal of Mass Spectrometry · 1997 · 21 citations · 0 references
Natural SciencesChemistryAnalytical ChemistryMass Spectrometric AnalysisOrganic ChemistryFragmentation AnalysisMass SpectrometryRadical ReactionsStructural ElucidationFragmentationFragmentation PathwaysIsotope Labeling ExperimentsMass Spectral FragmentationOxonium IonsSiliconTandem Mass SpectrometryTandem Mass Spectrometry Analysis
Two fragmentations of (CH3)3SiO-CR2-X-CR2-OSi(CH3)3, where X is a rigid group such as a triple bond or an aromatic ring, are losses of a methyl or R group (where R is H or alkyl). The metastable-ion dissociations of [M-R]+ and [M-CH3]+ ions include the rearrangement of a trimethylsilyl (TMS) cation and a (CH3)2Si = O neutral species through an ion-neutral complex. On the basis of tandem mass spectrometry (MS/MS), exact mass measurement and isotopic labeling experiments, it has been established that the two trimethylsilyloxy groups in the TMS ethers interact across a wide range of distances via an ion-neutral complex. The migration of a TMS cation occurs when the group that is bound to carbon is expelled as a radical by an oxygen-directed cleavage to give a trimethylsilylated oxonium ion. If, on the other hand, a methyl radical is lost from the silicon atom, then (CH3)2Si = O migrates. The mobilities of the TMS cation and the neutral (CH3)2Si = O are governed by the capability of the rigid group to delocalize charge.