Ortho effects in organic molecules on electron impact 13—mechanism of decarboxylation in o-carboxy heteroaromatics

Expulsion of CO₂ from the molecular ions of the 2-(2-carboxyphenyl) derivatives of benzoxazole, benzothiazole and benzimidazole gives rise to the base peaks on electron impact. The proposed mechanism for this fragmentation process, involving the anchimeric assistance of the heteroatom by the initial abstraction of the H˙ from the carboxyl group followed by the expulsion of CO₂ from the molecular ions, is supported by the study of the linked scan spectra.