title: Electron ionization induced fragmentation of some oxadiazole and thiadiazole derivatives.
abstract: The mass spectrometric behaviour under electron ionization of several 3,4-(alkyl/aryl)-disubstituted 1,2,4-oxadiazole-5(4H)-ones (1-13) and 1,2,4-thiadiazole-5(4H)-thiones (14-17), and that of 3-aryl-5-alkyl- or arylthio-1,2,4-thiadiazoles (18-24), was studied. These five-membered rings split similarly to the corresponding 1,2,4-thiadiazole-5(4H)-ones, although substitution has also a clear effect on the routes of fragmentation and the magnitude of secondary processes. In particular, the fragmentation of 1,2,4-oxadiazole-5(4H)-ones (1-6), which do not bear aromatic substituents, was, in addition to the ring ruptures, fairly complicated. The other compounds fragmented more systematically and relatively few unpredictable fragmentations occurred.
authors.affiliation: Department of Chemistry, University of Turku, FIN-20014 Turku, Finland. kpihlaja@utu.fi
authors.forename: Kalevi
authors.initials: K
authors.lastname: Pihlaja
authors.forename: Hikmet
authors.initials: H
authors.lastname: Agirbas
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ovcharenko
authors.forename: Pauliina
authors.initials: P
authors.lastname: Valtamo