The Influence of the C-4′ Substituent on the Formation of Benzoyl Ions during Electron Ionization-Induced Decomposition of Some 2-Phenyl-1,3,4-Oxadiazoles

Abstract

The effect of the C-4′ substituent for the formation of benzoyl ions during electron ionization-induced decomposition of some 2-phenyl-1,3,4-oxadiazoles is studied. The formation of these ions occurs via an azirane ion. The sums of the abundances of benzoyl ions and abundances of fragment ions derived from them, expressed as a percentage of total-ion current, were compared with the calculated charge density on both C-4′ atoms and atoms connected with C-4′ atoms. Linear correlations were found for both molecular and intermediate azirane ions. In the case of substituents which are less likely to be positively charged, the peaks of benzoyl ions have higher relative intensities. It is deduced that ionization in the phenyl ring strongly affects the formation of benzoyl ions from molecular ions of the studied compounds.