Collision-induced oxygen addition to chloroaromatic compounds

The reactions of chloroaromatic radical anions with oxygen were studied with a triple quadrupole mass spectrometer. Two chlorobenzenes and eight polychlorinated biphenyls were analyzed by gas chromatography-tandem mass spectrometry under negative ion chemical ionization. The molecular radical anions were selected with the first quadrupole and reacted with oxygen in the collision cell. Under these conditions, [M+O - Cl] ions were obtained with intensities similar to those of the transmitted precursor ions. This dechlorination reaction was not affected by a detectable chlorine isotope effect. The intensities of the [M+O - Cl] ions vary with the nature of the chloroaromatic compounds and with the oxygen pressure and collision energy. Charge transfer reactions are also observed, and the relative amount of O 2 (-.) produced is controlled by the relative electron affinity of the organochlorine. At high collision energies, collision-induced fragmentation of the molecular ion competes for the production of Cl(-).