Abstract
Ionic decomposition reactions of n‐alkanes under electron impact have been explored by studying the mass spectra of multiply deuterated undecanes and dodecanes and of octane‐1‐d. Label retentions in fragment ions in 70‐V spectra were supplemented by voltage dependence measurements and by metastable peaks. Alkanes appear to break down mainly by initial nonselective cleavage of carbon—carbon bonds, followed by further stepwise decomposition of the primary products, with intervening energy‐releasing rearrangements to give a characteristic product distribution.