✍ Scribed by Kalevi Pihlaja; Marja Himottu; Vladimir Ovcharenko; György Göndös; Lajos Gera; Gábor Bernáth
No coin nor oath required. For personal study only.
The electron-impact (EI) and collision-induced dissociation (CID) spectra of the title compounds were studied. The main fragmentation routes of M" ions included losses of hydrocarbon species and the formation of ArCNH' cations. The geometry of ring annelation predictably affected the stabilities of the molecular ions and the relative abundances of some characteristic fragment ions. The abundance ratios [M-H]'/M+', which were higher for trans-annelated isomers, correlated with the electronic effects of aromatic ring substituents. Molecular ions and [M -HIt ions of stereoisomers gave different CID spectra, suggesting that stereochemical differences are still preserved after the loss of hydrogen from M" ions. The stereochemical effects in the EI spectra were more pronounced at lower impact energies (16-24 eV). Several criteria for differentiating cis-and trans-annelated isomers based on the relative abundances of characteristic fragment ions were established.
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