Ion-molecule reactions of benzoyl ions in a quadrupole ion trap mass spectrometer

Studies using quadrupole ion trap mass spectrometry show that gas phase 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 hydroxy groups. The formation of [M + C(6)X(5)CO](+), [M-H](+) and [M - OH](+) products is determined by the hydroxy group environment in agreement with the known thermochemistry of these. ions and a molecular modelling study of the electrophilic addition. Storing the benzoyl ion at higher values of the ion trap q(z) parameter during the reaction reduces 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, allowing the selectivity of its reactions to be controlled. Reaction of [C6H5CO](+) and [C6F5CO](+) with unsaturated compounds yielded the corresponding adduct ions, whilst the formation of adduct and [M - Cl](+) product ions was observed only for the reaction of [C6F5CO](+) with chlorine-containing molecules, The potential of the benzoyl ion and substituted benzoyl ions as selective chemical ionisation reagents is illustrated for the product related intermediates of 2-(8-phenyloctyl)benzaldehyde separated by GC.