Mass-spectrometric study on ion-molecule reactions of CH5+, C2H5+ and C3H5+ with anilines, nitrobenzene, and benzonitrile

The gas-phase ion-molecule reactions of CH5+, C2H5+, and C3H5+ with five mo nosubstituted benzenes carrying a nitrogen atom in the substituent [PhX: X = NH2, NHCH3, N(CH3)(2), NO2, CN] have been studied using an ion-trap type of GC/MS at a low chemical-ionization gas pressure of CH4. The major produc t channels for anilines with low ionization potentials are proton transfer and charge transfer, while the channel for PhNO2 and PhCN with high ionizat ion potentials is proton transfer. The PhX+/(PhX+H)(+) ratios increases wit h decreasing the acidity of the reactant hydrocarbon ion and decreasing the ionization potential of reagent. Small amounts of initial adduct ions, pro duced by radiative association, and their decomposition products are found in the reactions with C2H5+ and C3H5+. The reaction mechanism is discussed based on product ion distributions and semi-empirical calculations of the e nergies of intermediates and products.