Selected ion flow tube studies of the reactions of H3O+, NO+ and O2+ with several amines and some other nitrogen-containing molecules

We report the results of a selected ion flow tube study at 300 K of the reactions of H3O+, NO+, and O-2(+) with ammonia, five primary, three secondary, and two tertiary amines, pyrrole and pyridine, and acetonitrile and benzonitrile. The major product ions of all the H3O+ reactions are the protonated parent molecules, MH+, these being the single product in six of these reactions; NH4+ is seen to be a minor product of three of the primary amine reactions, and ions of the type (M-H)(+) are minor products of the secondary and tertiary amine reactions. The low ionisation energies of all the amines, pyrrole, and pyridine ensures that charge transfer occurs in their reactions with NO+, this generally being sufficiently exothermic to result in partial fragmentation of the (M+)* nascent product ions resulting in (M-H)(+) and (M-CH3)(+) ions. However, charge transfer is endothermic between NO+ and pyridine and the two nitriles and then ion-molecule association occurs, producing the adduct ions NO+. M. The reactions of the more energetic O-2(+) ions with all the amines proceed via dissociative charge transfer, producing major products ions of the type (M-R)(+), where R is the alkyl radicals, CH3, C2H5, etc., as appropriate, but the parent cations, M+, are the single product ions for the reactions of the more stable aniline, pyrrole, pyridine, and benzonitrile. (C) 1998 Elsevier Science B.V.