Mass Spectrometry of Organogermanium Compounds Mechanism of Base Peak Ion Formation for 1, 1-Dimethylgermacyclohexane

Abstract

So far, studies on mass spectrometric fragmentation processes of organogermanium cornpounds have been reported mostly for acyclic systems. In this paper, we report the mass spectrometric fragmentations caused by electron impact and their analysis for 1, 1-dimethylgermacyclohexane(1 ) and related compounds.
The main path of fragmentation of 1 is a loss of an ethylene moiety from the molecular ion, and a subsequent loss of a cyclopropane moiety to yield a dimethylgermyl cation radical. A loss of a methyl radical from the dimethylgermyl cation radical yielded methylgermyl cation which forms the base peak (m/z 89 for the hydrogen compound or m/z 92 for the deuterium compound). A further loss of a methyl moiety yielded a germanium ion. It was found that the main pathway is accompanied by other minor pathways.
The proposed pathway was confirmed by the shift method, i. e., a comparison of fragmentation pattern between the parent and appropriately substituted species. In this study, 1, 1, 3and 1, 1, 4-trimethylgermacyclohexanes(3 and 5) and 1, 1-bis(trideuteriomethyl)derivatives of 3 and 5 were analyzed.
For all of th e compounds investigated the base peak ions are identical, and ions which contain a germanium atom are more abundant than those without.