The Mass Spectrometric Fragmentation of 1-Alkyl Ions derived from Halides

The mass-spectrometric fragmentation of n-pentyl, n-hexyl, n-octyl and n-nonyl ions has been studied using ¹³C- and D-labelling. The ions were produced from the corresponding halide ions. The loss of an olefin as a neutral fragment is the main reaction. The elimination of this fragment must be by a complex mechanism, since the terminal carbon atoms have the smallest probability of being lost with the neutral fragment. On chains with five to six carbon atoms, hydrogen scrambling seems to preceed the fragmentation; this is not true for hydrogen on terminal positions of longer chains. Ring formation prior to the fragmentation could explain some of the results; but no reasonable conclusion could be reached.