Labelling studies of hydrogen rearrangements in the chemical ionization mass spectra of cyclohexanone and its derivatives

Deuterium labelling studies indicate that loss of water from the protonated molecular ion of cyclohexanone involves competitive site‐specific eliminations. Loss of alcohol from the protonated molecular ions of 4‐alkoxycyclohexanones involves competition between a direct cleavage, a 1,3‐hydrogen rearrangement and consecutive losses of alkene and water.