Doubly Charged Ion Mass Spectra of Monosubstituted Aromatic Compounds

The 2E doubly charged ion mass spectra of twelve simple monosubstituted aromatic compounds were recorded. The spectral pattern of these compounds can be classified into three types. When the substituent is strongly electron-donating such as the amino or dimethylamino group, a very intense molecular ion peak appears, no fragment ion peak being observed. Phenol, anisole, toluene, and chlorobenzene show both molecular and fragment ion peaks in varying intensities. The parent benzene itself behaves similarly. Only fragment ion peaks were observed for nitrobenzene and aromatic carbonyl compounds such as benzaldehyde, acetophenone, methyl benzoate, or benzoic acid. The major fragmentation reactions are discussed.