Studies in organic mass spectrometry. Part 9—mass spectra of 9,10‐disubstituted 2,3,6,7‐tetraalkoxy‐9,10‐dihydroanthracenes: A remarkable loss of radicals from even‐electron ions

The electron impact‐induced fragmentations of 23 9,10‐disubstituted 2,3,6,7‐tetraalkoxy‐9,10‐dihydroanthracenes, including six stereoisomeric pairs, were studied. The loss of the 9‐(or 10‐)substituent constitutes the main fragmentation route. The resulting ions give rise to a remarkable violation of the so‐called ‘even‐electron rule’ as they eject the second substituent at the 10‐(or 9‐)position as a radical. The latter aspect was particularly investigated with the aid of low‐energy (nominal value 15 eV) and mass‐analysed ion kinetic energy spectra.