Investigation of Group Migration in the Fragmentation of Bis(trimethylsilyl) Ethers of Diols Separated by Rigid Groups

• Published in: Journal of mass spectrometry. 1997-01, Vol.32 (1), p.71-80
• Main Authors: Byun, Jaeman, Gross, Michael L., George, Mathai, Parees, David M., Kamzelski, Ann Z., Swijter, Dennis F. H., Willcox, Dale A.
• Format: Article
• Language: English
• Subjects: Chemistry; diols; Ethers - chemistry; Ethers - metabolism; Exact sciences and technology; fragmentation mechanisms; group migration; ion-neutral complexes; Ions; Mass Spectrometry; Molecular Structure; Organic chemistry; Reactivity and mechanisms; tandem mass spectrometry; TMS ethers; Trimethylsilyl Compounds - analysis; Trimethylsilyl Compounds - chemistry; Trimethylsilyl Compounds - metabolism
• ISSN: 1076-5174; 1096-9888
• DOI: 10.1002/(SICI)1096-9888(199701)32:1<71::AID-JMS452>3.0.CO;2-9

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. © 1997 by John Wiley & Sons, Ltd.