ION-MOLECULE REACTIONS OF BENZOYL IONS IN A QUADRUPOLE ION-TRAP MASS-SPECTROMETER

Studies using quadrupole ion trap mass spectrometry show that gas phas e benzoyl ions, of the type [C(6)X(5)CO](+) (X = H, F, 4-Me, 4-Bu(t)) undergo selective ion-molecule reactions with compounds containing hyd roxy groups. The formation of [M + C(6)X(5)CO](+), [M-H](+) and [M - O H](+) products is determined by the hydroxy group environment in agree ment with the known thermochemistry of these. ions and a molecular mod elling study of the electrophilic addition. Storing the benzoyl ion at higher values of the ion trap q(z) parameter during the reaction redu ces adduct ion intensity, due to an increased rate of dissociation of the adduct, Substitution of the benzoyl ion with fluorine or a methyl group modifies the electrophilic character of the benzoyl ion, allowin g the selectivity of its reactions to be controlled. Reaction of [C6H5 CO](+) and [C6F5CO](+) with unsaturated compounds yielded the correspo nding adduct ions, whilst the formation of adduct and [M - Cl](+) prod uct ions was observed only for the reaction of [C6F5CO](+) with chlori ne-containing molecules, The potential of the benzoyl ion and substitu ted benzoyl ions as selective chemical ionisation reagents is illustra ted for the product related intermediates of 2-(8-phenyloctyl)benzalde hyde separated by GC.