Gas-phase reactions of the oxygen radical anion with arylalkylamines

The gas-phase reactions of the oxygen radical anion O.- with a number of biologically active arylalkylamines of general formula (RC6H4CHR2)-C-1 (CH2)(n)NHR3, where R-1 = H, F, NO2, OH, or OCH3, R-2 = H or OH, and R-3 = H or CH3, have been studied by means of chemical ionization mass spectrometry, using a mixture of N2O and N-2 (1:9) to generate the O.- reagent ions. The collision-induced dissociation spectra of the [M-H+O](-) adduct ions formed in the ion source of the mass spectrometer have been interpreted in terms of the aliphatic chain length and the presence of different functional groups in the molecule. The analysis of data indicates that the preferred site of oxygen radical anion attachment is the benzylic carbon atom, except for the amines with a benzylic hydroxy group (octopamine and synephrine), where a competition between the aromatic ring and the benzylic carbon atom, becomes evident. The fragmentation pathways observed for octopamine and synephrine are unique as compared with all the other amines, in which the chain length also exerts an important influence on the observed decompositions. (C) 2001 Elsevier Science B.V.