Mass spectra of allenic compounds substituted with a hydrocarbon chain bearing a heteroatomic group (hydroxy, alcoxy, halogen, dialkylamino) or a phenyl in the γ position exhibits a strong peak corresponding to the loss of C2H4 (28a. mu) from the molecular ion. This is commonly the base peak of the spectra and due to a McLafferty type transfer of the heteroatom or phenyl group to the central allenic carbon atom. The methyl group shows a ...