The mass spectra of the trimethylsilyl derivatives of glycerophosphoric acids. Inter- and intra-molecular rearrangements of siliconium ions

Abstract

The trimethylsilyl derivatives of several glycerophosphoric acids are taken as model compounds for an investigation of the fragmentation mechanisms producing the characteristic ions present in the mass spectra of trimethylsilyl derivatives of organic phosphates of this type. A considerable number of rearrangement ions formed by migration of hydrogen atoms and/or trimethylsilyl groups are observed. The presence of a fully substituted phosphonium system is thought to contribute to the stability of these ions. A close similarity between the migratory properties of hydrogen atoms and trimethylsilyl groups is apparent. The spectra of the trimethylsilyl derivatives of the diphosphates exhibit ions produced by the interaction and rearrangement of intact trimethylsilyl phosphate groups. Ion–molecule reactions involving the combination of a neutral molecular species with an abundant fragment ion containing a siliconium centre are also observed. These ion–molecule reactions provide additional information regarding the structure of some of the fragment ions.