ELECTRON-IMPACT INDUCED FRAGMENTATION OF ALKYLTHIOPYRIDINES . EXTENT OF RING NITROGEN INVOLVEMENT

The fragmentation patterns obtained upon electron impact of 2‐, 3‐, and 4‐alkylthio‐pyridines were examined to determine the extent that the ring nitrogen is involved. The effect of the size of the alkyl group, as well as the ring position of the sulfide on the fragmentation of the methyl‐, ethyl‐, n‐propyl‐, n‐butyl‐ and t‐butylthiopyridines, is discussed. The mass spectrum of 2‐n‐octylthiopyridine is also recorded. The molecular ions decomposed with rupture of the bonds α, β, γ, and δ from the hetero‐aromatic ring. The molecular ions also exhibited the loss of alkenes via a number of mechanisms, notably the loss of Cn‐1 H2n from the alkyl group of 2‐alkylthiopyridines by a transition involving the rupture of a C‐C bond γ to the ring and the transfer of a proton on a carbon ϵ to the ring. The role of the pyridine sp2 nitrogen in this and other fragmentations is discussed. An elimination of HS radical is also observed in a number of these alkylthiopyridines. Copyright © 1969 Journal of Heterocyclic Chemistry