Reactions of alkyl siliconium ions under chemical ionization conditions

MASS SPECTROMETRIC FRAGMENTATION OF TRIMETHYLSILYL AND RELATED ALKYLSILYL DERIVATIVES

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy- and amino-acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di- and trialkyl-silyl derivatives, various substituted-alkyldimethylsilyl derivatives such as the tert-butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3-pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1-107, 2019.

Radiative stabilization of trimethylsilyl adduct ions

Ketones and phenol react with trimethylsilyl ions to form adduct ions by radiatively or collisionally stabilized addition reactions, in contrast to aliphatic alcohols and ethers, which react with trimethylsilyl ions to form adduct ions by a rapid two-step process. Secondorder rate constants for the addition of trimethylsilyl ions to acetone were independent of pressure from 3×10(-7) to 50×10(-7) tort at room temperature; consequently, the adduct ions, [M+73](+), are formed primarily by radiatively stabilized addition in these ion cyclotron resonance experiments.