Mass spectrometry of xanthones‐I: The electron‐impact‐induced fragmentation of xanthone, monohydroxy‐ and monomethoxyxanthones

With the aid of isotopic labelling (D and 18O) and the metastable defocusing technique the mass spectra of xanthone, the monohydroxyxanthones and the monomethoxyxanthones have been recorded and interpreted. The relative position of the hydroxy group exerts no direct effect on the fragmentation, whereas the decomposition of the methoxy compounds is clearly influenced by the position of the substituent. The 1‐methoxy‐group exhibits an ‘Ortho‐effect’. The presence and significance of doubly‐charged ions in the spectra are discussed.