TETRAMETHYLSILANE CHEMICAL-IONIZATION MASS-SPECTROMETRY OF MONOSUBSTITUTED AROMATIC-COMPOUNDS - GAS-PHASE TRIMETHYLSILYLATION

The tetramethylsilane (TMS) chemical ionization (CI) spectra of the mo no-substituted aromatics studied contain M(+.) and adduct [M + (CH3)(3 ))Si](+) ions. Abundant M(+.) ions are observed in compounds with elec trondonating groups and are attributed to charge-exchange reactions of reactant ions in the TMS CI plasma. The stability of adduct ions in t he halobenzenes was found to increase from fluorobenzene to iodobenzen e. A collision-induced dissociation study of the [M + (CH3)(3)Si](+) i ons of these compounds has been carried out to gain an insight into th e site of adduction.