Stereochemical Effects In The Mass Spectra Of Cis- And Trans-2-Aryl-4a,5,6,7,8,8a-Hexahydroquinazolin-4(3h)-Ones

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-H](+) 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.