METASTABLE ION STUDY OF ORGANOSILICON COMPOUNDS .8. DIMETHOXYDIPHENYLSILANE

The spontaneous unimolecular dissociation reaction of the molecular io n of dimethoxydiphenylsilane (1) has been investigated by mass-analyze d ion kinetic energy spectroscopy, collision-induced dissociation, a D -labeling study and high resolution data. The results are compared wit h those of the corresponding carbon analogue, dimethoxydiphenylmethane (2). The fragmentation of the metastable 1(.+) is more complex than t hat of 2(.+). The latter eliminates the methoxy radical only, whereas the former eliminates methanol and benzene molecules, and C7H7 radical in addition to the formation of the molecular ion of biphenyl (3). Th e intensity of the [M-C6H5](+) ion at m/z = 167 is much larger than th at of [M-OCH3](+) ion at m/z = 213 in the normal mass spectrum of 1. O n the contrary, in the case of 2, the intensity of [M-C6H5](+) ions is smaller than that of [M-OCH3](+) ions.