Oxygen equilibration in the mass spectra of 2-benzoylbenzoic acid

Abstract

Positional integrity of the label is maintained in the molecular ions of 2-ben~oyl[¹⁸O]benzoic acid prior to a number of primary fragmentation modes. Positional integrity is also evident for some source and metastable reactions of the protonated molecular ions formed in its chemical ionization (H₂) mass spectrum. The (M-Ph)⁺ ions formed in the electron impact mass spectrum, however, fragment further after complete equilibration of their oxygen atoms.