Stereoisomeric effects on mass spectra—II: The isomeric methyldecalins

Mass spectra of the four stereoisomeric 1-methyldecalins and the four 2-methyldecalins have been measured. For each set of stereoisomers, the order of relative intensity of the parent-less-CH₃ ion, but not of the parent ion, parallels the order of relative stability of the molecules. The correlation suggests that loss of the methyl group from the members of each set of stereoisomers leads to a common product, with the differing conformational energies converting into differences in vibrational energy, which in turn lead to differing extents of further decomposition.     

Organic ions in the gas phase. Part XX. Mass spectra of phenylthiophenes

The mass spectra of 2- and 3-phenylthiophenes and their phenyl-d₅ counterparts reveal that the thienyl ring is markedly more reactive than the phenyl ring under electron impact. In one process, that leading to loss of C₂H₂S, the atoms lost are apparently derived solely from the thienyl ring, quite probably from the original molecular configuration.