Fragmentation Mechanisms of Butylmethylsilane, Butyldimethylsilane, and Butyltrimethylsilane Ions in EI Mass Spectrometry : 1. Experimental Approach

概要

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The unimolecular dissociation of the butylmethylsilane, butyldimethylsilane, and butyltrimethylsilane ions in EI mass spectrometry has been investigated using the deuteriumlabeling technique and the B/E linked scanning method. The EI mass spectra of these alkylsilanes were characterized by the formation of silyl cation, [(CH3)nSiH3-n]+ (n=1-3), due to the cleavage of an Si-C bond and the formation of [(CH3)nSiH3-nCH2=CH2]+ due to the cleavage of a Cβ-Cγ bond. The stabilization due to an Si-C hyperconjugation is found to be a driving force to produce [CH3SiH2CH2CH2]+ from butylmethylsilane ion and [(CH3)2SiHCH2CH2]+ from butyldimethylsilane ion, respectively. The present results show that the intensities of [(CH3)nSiH3-n]+ and [M-CH3]+, increase in the order of butylmethylsilane butyldimethylsilane butyltrimethylsilane, and that of [(CH3)nSiH3-nCH2CH2]+ increases in the reverse order. The EI mass spectra of the deuterium-labeled compounds show that [M-CH3]+ is produced due to the cleavage of an Si-CH3 bond. [M-H]+ in EI mass spectra of butylmethylsilane and butyldimethylsilane is produced due to the loss of a hydrogen atom connected to the Si atom. H2 elimination from the butylmethylsilane ion occurs due to 1,4-H2 elimination via a four-membered ring formation or 1,1-H2 elimination due to a loss of two hydrogen atoms connected to the Si atom.
日本質量分析学会の論文
1995-02-28