Metastable ion study of organosilicon compounds. Part V—tetramethoxysilane and trimethoxymethylsilane

Abstract

Abstract The fragmentations of tetramethoxysilane ((CH 3 O) 4 Si (1)) and trimethoxymethylsilane ((CH 3 O) 3 SiCH 3 (3)) induced by electron impact were investigated by mass‐analysed ion kinetic energy (MIKE) spectrometry and a deuterium‐labelling study. These molecular ions begin to fragment by the loss of CH 3 or CH 3 O. These fragmentations are followed by the loss of an aldehyde molecule (H 2 CO), as commonly observed in the mass spectra of alkoxysilanes. Almost complete scrambling of the methoxy hydrogens takes place in the metastable molecular ion, [1] + ˙, prior to the decomposition. On the other hand, a moderate extent of scrambling of the hydrogens takes place in [3] + ˙. The fragmentations of [1] + ˙ and [3] + ˙ were compared with those of the corresponding carbon analogues, tetramethoxymethane ((CH 3 O) 4 C (2)) and 1,1,1‐trimethoxyethane ((CH 3 O) 3 CCH 3 (4)), respectively.