ELECTRON-IMPACT-INDUCED FRAGMENTATION OF N-ALKYL CYANIDES

The mass spectra of the alkyl cyanides up to n‐pentyl cyanide were studied. Using metastablel ion transitions, appearance potentials and deuterium labelling, the fragmentation patterns, spectral characteristics and trends for this series can be given. The investigation of labelled compounds demonstrates the specificity of rearrangement and normal decomposition processes. Alkyl ions in nitriles are produced by simple cleavage of the carbon‐carbon bond, while ions of the type [M –alkyl]+, which at the first sight could originate in the same way, are presumably formed via cyclic intermediates and are in fact rearrangement ions. Apart from the known γ and δ‐hydrogen rearrangements, there is novel evidence for a β‐hydrogen rearrangement via a five‐membered ring transition state. Copyright © 1969 John Wiley & Sons, Ltd.