Low–energy,low-temperature mass spectra. 8—The McLafferty rearrangement

The McLafferty rearrangement giving rise to the McLafferty ion, the complementary ion and a protonated molecule is discussed in the cases of the alkenes, alkanals, alkanones, alkanoic acids and alkanoic esters, in terms of the low-energy, low-temperature mass spectra. Based on the behaviour of the alkanals, which show a series of peaks corresponding to [M ? C_nH_2n]⁺˙, it is suggested that these also involve McLafferty rearrangements from rearranged distonic ions. The same processes are held to be responsible for similar series of peaks in the case of the alkenes and that of the amines. Where possible the energetics of the processes concerned are discussed. The low-energy mass spectra of the linear alkenes propene to octene and those of the octenes are reported.