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Issue 11, 1996
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Combined quantum chemical and mass spectrometric study of [Si,C,H3,O]+ isomers


The potential energy surface of [Si,C,H3,O]+ has been explored by means of ab initio MO calculations at the G2 level of theory as well as by mass spectrometric techniques. The silicon–methoxide cation H3COSi+ has been identified as the global minimum (ΔfH= 151 kcal mol–1), followed by the silaacetyl cations H3SiCO+fH= 172 kcal mol–1) and H3CSiO+fH= 180 kcal mor–1). A number of other intermediates, the transition structures associated with the mutual interconversion reactions and the energetics of possible fragmentation channels are explored computationally. It turns out that the energy demands for the unimolecular isomerizations of most of the isomers are substantially lower than those of fragmentations. Consequently, an identification of the different isomers based solely on mass spectrometric information is made difficult by intramolecular rearrangements which precede the structure-indicative fragmentation reactions, even though H3SiCO+ is clearly distinguishable from H3CSiO+ and H3COSi+. However, when the experimental findings are combined with the computationally predicted [Si,C,H3,O]+ potential-energy surface and with thermochemical information, this difficulty can be overcome, and a coherent picture of this complex system emerges. In addition, the existence of the neutral radicals H3COSi˙, H3CSiO˙, as well as H3SiCO˙ and/or H3SiOC˙ is explored by means of neutralization–reionization mass spectrometry.

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Article type: Paper
DOI: 10.1039/P29960002389
Citation: J. Chem. Soc., Perkin Trans. 2, 1996,0, 2389-2399
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    Combined quantum chemical and mass spectrometric study of [Si,C,H3,O]+ isomers

    M. C. Holthausen, D. Schröder, W. Zummack, W. Koch and H. Schwarz, J. Chem. Soc., Perkin Trans. 2, 1996, 0, 2389
    DOI: 10.1039/P29960002389

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