| Summary: | Twelve 3-cyano-4-(substituted phenyl)-6-phenyl-2(1H)-pyridinones were investigated by tandem mass spectrometry using positive as well as negative electrospray ionization. The influence of the electron affinity of the substituent and the steric effect on the fragmentation is discussed. Pyridinones with a substituent of low proton affinity show loss of water, HCN or benzene from the pyridinone ring in the first step of MS2 fragmentations. Oppositely, if a substituent with high proton affinity is present on the phenyl ring in the 4-position of pyridinone, the fragmentation paths are complex, depending mainly on the substituent proton acceptor ability. Elimination of neutral molecules CO, HCN, H2O, PhH (benzene) or Ph and CN radicals are fragmentation processes common for all compounds in the subsequent steps of the fragmentations.
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