ISOMER DIFFERENTIATION IN 7, 12-DIMETHYLBENZ[A]ANTHRACENE-PYRIDINE ADDUCTS BY FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY

Three isomeric 7,12-dimethylbenz[a]anthracene-pyridine adduct salts, namely, the 5-N-pyridinium-7,12-dimethylbenz[a]anthracene perchlorate, the 7-N-pyridiniummethylene-12-methylbenz[a]anthracene picrate, and the 7-methyl-12-N-pyridiniummethylenebenz[a]anthracene picrate, were studied by fast atom bombardment tandem mass spectrometry using high energy collisional-activated dissociation (CAD). The CAD mass spectra of the molecular cations and the (M - pyridine)+ ions allow one to distinguish positional isomers on the basis of daughter ion peak height ratios. The differences in the CAD mass spectra of the (M - pyridine)+ ions are probably due in part to formation of isomer-specific fused-ring tropylium ions.