The mass spectral fragmentation patterns of a various 2,4-dinitrophenyl-4′-substituted phenyl sulfides and sulfones help define the role of substituent effects under electron impact, and subsequently determines the appearance of the base peak. These substituent effects correlated well with the Hammett σ-values. The mass spectral features arise from the elimination of the sulfur atom with recombination of the terminal end groups or with scission across 4′-substituted phenyl ring in sulfides, whereas in sulfones the most abundant ion is formed through the sci-ssion of the rearranged aryl sulfinate ester. A comparison between the spectra of the two types is discussed. The results suggest that the skeletal rearrangement of the molecular ion occurring in these S-bridged compounds is a sensitive diagnostic tool in structure elucidation.