ELECTRON IONIZATION MASS-SPECTRA AND CRYSTAL-STRUCTURES OF SOME [1,2,4]TRIAZOLO[1,2-B]PHTHALAZINES AND [1,3,4]THIADIAZOLO[3,4-B]PHTHALAZINES

The mass spectra of ten 1,3-dithioxo[1,2-4]triazolo[1,2-b]phthalzaines , five 3-iminosubstituted 1-thioxo-[1,3,4]thiadizaolo[3,4-b]phthalazin es, three ituted-1-thioxo[1,2,4]triazolo[1,2-b]phthalazines, and o-5,1 0-dihydro[1,3,4]thiadiazolo[3,4-b]phthalazine were recorded under elec tron ionization. The fragmentation pathways were elucidated by metasta ble ion analysis and exact mass measurements. The changes in the ring- system had little effect on the fragmentation mechanism, but the effec t on peak intensities was considerable. The most important fragmentati ons began with the opening of the triazole ring. Substituents at nitro gen atoms also had a marked effect on the mass spectral behavior. The aryl substituents prompted a whole new fragmentation. The X-ray crysta l structure was determined for a few compounds. Two of the three struc tures of the 1,3-dithioxo[1,2,4]triazolo[1,2-b]phthalazines that were studied proved to be relatively planar, whereas the structure of -5,10 -dihydro[1,3,4-]thiadiazolo[3,4-b]phthalazine was considerably bent si milarly to the 5,10-tetrahydro[1,2,4]triazolo[1,2-b]-phthalazine. The triazole and the thiadiazole rings had a strong double bond nature.