Investigation of group migration in the fragmentation of bis(trimethylsilyl) ethers of diols separated by rigid groups.
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.
Byun
J
J
Department of Chemistry, Washington University, St Louis, MO 63130, USA.
Gross
M L
ML
George
M
M
Parees
D M
DM
Kamzelski
A Z
AZ
Swijter
D F
DF
Willcox
D A
DA
D004987:Ethers / Q000737:chemistry / Q000378:metabolism*; D007477:Ions; D013058:Mass Spectrometry; D015394:Molecular Structure; D014297:Trimethylsilyl Compounds / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
D004987:Ethers; D007477:Ions; D014297:Trimethylsilyl Compounds