抄録
Mass spectra(MS)of 1-phthalazinecarbonitrile(Ia), 1-substituted 4-phthalazinecarbonitriles(Ib to If)and 1-substituted 1, 2-dihydro-4-phthalazinecarbonitriles(Ig and Ih)were examined. The main fragmentation of Ia proceeds by the expulsion of nitrogen molecule from the molecular ion(M+). In MS of Ib, Ic, Ie and If, the principal dissociation of ring system proceeds by the. expulsion of·N2H radical from M+ or(M-· EH)+ species. When the alkyl substituent at the 1-position is the methyl group(Ib), the intensity of resulting (M-·N2H)+ species is greater than that of(M-HCN)+ species. In turn, when the substituent at the 1-position is the ethyl (Ic), benzyl(Ie)or phenyl(If), the intensity of(M-· H-· N2H)+· species is smaller than that of(M-· H-HCN)+ species. These facts mean that the facility for the ring cleavage by the expulsion of. N2M radical from M+ or(M-· H)+ species is inversely proportional to the relative size of the substituent at the 1-position. Other dissociation of ring system proceeds by the expulsion of carbon and nitrogen at the 1-and 2-positions or at the and 3-positions caused by the scission of bond between adjacet nitrogen atoms at the 2-and 3-positions. The fragmentation of 1-isopropy l-4-phthalazinecarbonitrile(Id)proceeds by the dissociation of isopropyl group. The main fragmentation of Ig and Ih proceeds by the expulsion of the substituent at the1-position to give the cyanophthalazinium ion.
