Effect of ortho substituents in the electron impact induced fragmentation of 2,2′‐disubstituted stilbenes

Abstract

AbstractThe effect of ortho substituents NH2, OCH3, CH3, Cl and NO2 on the fragmentation of five symmetrically and five unsymmetrically 2,2′‐disubstituted stilbenes under electron impact was investigated. The fragmentation patterns deduced were supported by metastable transitions in the first and second field free regions and by exact mass measurements of prominent ions. In general, the fragmentation was found to be in accord with that of stilbene and the corresponding monosubstituted stilbenes. There are, however, some deviations from the general fragmentation scheme caused by direct through‐space interactions of the ortho, ortho′ substituents with concomitant loss of neutral fragments. It is supposed that the formation of 7‐membered cyclic or heterocyclic ions is the result of such through‐space reactions.