Stereochemical effects in the electron impact mass spectra of cis‐trans isomeric 1,2,3,4‐tetramethylcyclohexanes

The mass spectra of six cis‐trans isomeric 1,2,3,4‐tetramethylcyclohexanes are discussed. The intensity ratio of [MCH 3 ] + /[MC 2 H 5 ] + correlates with the strain energies of the stereoisomers. Therefore, the identification of cis‐trans isomers is possible by means of their mass spectra. The mass spectra of deuterium labelled compounds demonstrate favoured fragmentation of the axial methyl groups and ring opening between the cis substituted carbon atoms of the cyclohexane.