PUB - Publikationen an der Universität Bielefeld

The electron impact induced fragmentations of some hexaalkyl disiloxanes have been studied with respect to the effect of the size and the positions of different alkyl substituents at the Si-atoms. Positional isomers of hexaalkyl disiloxanes differing by the distribution of alkyl groups over both Si-atoms can be easily distinguished by large intensity differences of fragment ions in the 70eV EI-mass spectra. D-labelling studies and MIKE-spectra of relevant ions show that this effect is due to an unusual preference for the loss of a small alkyl group flanked by two larger ones at the same Si-atom from molecular ions. The results also indicate that after the initial loss of an alkyl radical the structural identity of the fragment ions is lost probably by migrations of alkyl groups.