Molecular orbital approaches to the interpretation of organic mass spectra

High and low resolution mass spectral data are presented for a series of seven ψ-1,3,4-thiadiazole- 2-thiones; seven other mesoionic heterocycles and two nonmesoionic analogs of the ψ-1,3,4-thiadiazole- 2-thione ring system. The fragmentation pathways for the mesoionic systems and the marked differences with the non-mesoionic analogs can be easily rationalized by application of MO theory. In its present form, this MO interpretation is an extension of the usual resonance approach to the explanation of mass spectral reactions, which has been successfully applied to other heterocycles.