Metastable and Collision-induced Dissociations of Organosilicon Compounds.

Unimolecular Gas-phase Reactions of Organosilicon Compounds. Part XV. Acetyltrimethylsilane, CH₃COSi(CH₃)₃

“…19) A similar migration, that is a 1,2-shift of the C 6 H 5 group in (CH 3 ) 2 SiCOC 6 H 5 ῌ , occurs prior to CO elimination. 23) On the basis of these reported and our present results, we can conclude that trimethylsilyl ions at m/z 73 are generated by the loss of CO from both (CH 3 ) 3 SiCO ῌ and (CH 3 ) 2 SiCOCH 3…”

“…The former is due to the loss of methyl from the acetyl group and the latter is due to methyl loss from the trimethylsilyl group. That is, the m/z 101 ions generated from 1 ῌῌ consist of two isomeric ions, (CH 3 ) 3 SiCO ῌ and (CH 3 ) 2 SiCOCH 3 ῌ . In the metastable time window, the molecular ion 1 ῌῌ decomposes exclusively into the ion at m/z 101 by the loss of a methyl radical.…”

“…1), 7), 8) A trimethylsilyl ion, (CH 3 ) 3 Si ῌ , is usually observed at m/z 73 in the mass spectra of the compounds, which contains a trimethylsilyl group. 5), 9) Many authors in the field have utilized trimethylsilyl ions as one of the reactants in ion-molecule reactions.…”

“…Unimolecular decompositions of ionic organosilicon species, generated by electron ionization, have been studied extensively, 2), 3) and compared with those of the corresponding carbon analogues. 4)῎7) It is well known that extremely complex fragmentation pathways have been observed, even for simple organosilicon compounds.…”

“…The latter reaction occurs via a 1,2-shift of the methyl group, 19), 23) and is associated with a large KER value (T 0.5 ῌ329 meV) in agreement with that of a rearrangement mechanism. 19) This means that the trimethylsilyl ions, (CH 3 ) 3 Si ῌ , at m/z 73 are generated by at least three di#erent routes as summarized in Scheme 1.…”