INFLUENCE OF PROXIMITY EFFECT ON THE EI MASS-SPECTRAL FRAGMENTATION OF DIHYDROXY AND DIMETHOXY 2,2'-BIPYRIDINES AND THEIR N,N'-DIOXIDES

The mass spectral fragmentation of 3,3' and 4,4'-dihydroxy as well as of the dimethoxy substituted derivatives of 2,2'-bipyridines and their N,N'-dioxides was studied. Fragmentation pathways, the elucidation of which was assisted by accurate mass measurements and metastable trans itions, are proposed. These results clearly show the proximity effect along with pi-electron conjugation to be responsible for the initial 3 ,3'-isomer fragmentations and create a reliable basis on which it is p ossible to distinguish between the different regio isomers. The relati onship between the structure features and the mode of .OH ejection is discussed.